AN ABSTRACT OF THE THESIS OF
Sookapracha Vachananda
(Name)
in
Chemistry
presented on
(Major)
Title:
for the Doctor of Philosophy
(Degree)
(Date)
A STUDY OF THE LIMITATIONS OF ULTRAVIOLET
SPECTRAL DATA FOR THE DETERMINATION OF DISSOCIATION
CONSTANTS OF ORGANIC NITROGENEOUS BASES
Abstract. approved
Redacted for Privacy
(Major professor)
Ultraviolet spectroscopic methods for the determination of dissociation constants can only be applied to
those compounds having protonatable sites conjugated with
or inherent in a chromophoric group of the compound.
The determination of the dissociation constants of
organic nitrogeneous bases by ultraviolet spectroscopic
methods was found to be only reliable for those compounds
having a single protonatable site in or conjugated with
the chromophoric group of the heterocycle.
With such compounds both methods,
(I)
those based on
taking the extinction coefficient profile over the entire
pH range at selected wavelengths, and
a
(II)
those based on
measurement of the pH at which the ;,max
hoax, value was
approximately the average for the protonated and unprotonated forms at
a
selected wavelength, were in fair
agreement with one another and with dissociation
constants determined by potentiometrics,
conductometric
and other methods.
With those compounds having two protonatable sites,
both weakly basic,
there was found to be approximately
fair agreement between methods
I
and II and with those
determined by other procedures, but not in all cases.
Method II did not lend itself to the measurement of more
than
a
single constant when several constants were pres-
ent in a compound
Those compounds having two protonatable sites, one
weakly basic and the other weakly acidic, also gave
approximately fair agreement between methods
I,
II and
published data.
The amino acids likewise gave only fair approximations with methods
I
and II and those recorded in the
literature.
With compounds having three or more protonatable
sites in the chromophore there was poor agreement between
methods
I
and II as well as with those determined by
other procedures.
Method
I
was found to be capable of measuring
several dissociation constants when more than one oc-
curred with
a given.
compound.
Moreover, the most
reliable information was obtained by taking the extinction coefficient profile over the entire pH range at
10
mil
intervals over the entire ultraviolet spectra.
This was especially helpful for measuring dissociation
constants which were of approximately the same order
associated with
Method
I
a
gave
given chromophoric group.
a
number of dissociation constants
for compounds having several protonatable
sites within
the chromophoric group for certain compounds which had
not been measurable by other procedures.
Included in
these observations was evidence of the deprotonation of
amino substituent in alkaline media in
a
fairly large
number of instances.
A number of unreported dissociation constants of
known compounds are herein documented.
A STUDY OF THE LIMITATIONS OF
ULTRAVIOLET SPECTRAL DATA FOR THE
DETERMINATION OF DISSOCIATION CONSTANTS
OF ORGANIC NITROGENEOUS BASES
by
SOOKAPRACHA VACHANANDA
A THESIS
submitted to
OREGON STATE UNIVERSITY
in partial fulfillment of
the requirements for the
degree of
DOCTOR OF PHILOSOPHY
June 1967
APPROVED:
Redacted for Privacy
Professor of Chemistry
In Charge of Major
Redacted for Privacy
Chairman of Department of Chemistry
Redacted for Privacy
Dean of Graduate School
Date thesis is presented
Typed by Erma McClanathan for
ri,
i
%
-!
ACKNOWLEDGMENTS
The author wishes to express sincere appreciation
to Dr.
Bert E. Christensen for his guidance in preparing
this thesis.
Without his patient and helpful suggestions
this work would not have been possible.
Thanks also are due the Rockefeller Foundation for
financial support; and the Department of Chemistry,
Oregon State University, for the Teaching Assistant
granted.
In addition,
the author is grateful to Kasetsart
University and the Government of Thailand for granting
leave of absence.
TABLE OF CONTENTS
Introduction
Introduction...
............................
Results and Discussion
Experimental
......
....... ....... .....
.a
1
17
47
Summary
206
Bibliography
209
Appendix
Abbreviations .............o........... 213
LIST OF FIGURES
Figure
1.
2.
Dissociation of Phenol by Method of
Stenström and Goldsmith
5
Dissociation of Benzoic Acid as an Acid by
Method of Flexser et al
8
3.
A Typical Spectral Transmission Curve
4.
E versus pH of
5.
E
6.
7.
51
I
versus pH of p-Aminophenylacetic Acid
by Method I
53
E versus A of p- Aminophenylacetic
by Method II
55
Acid
E versus pH of Aniline Hydrochloride
by Method
8.
Acetanilide by Method
12
57
I
versus A of Aniline Hydrochloride by
Method II
E
59
9.
E versus pH of Benzoic Acid by Method
I
61
10.
E versus pH of Benzoic Acid by Method
I
62
11.
E versus A of Benzoic Acid by Method II
64
12.
E versus pH of N,N- Dimethylaniline by
Method
13.
66
I
E versus A of N,N- Dimethylaniline by
Method II
14.
E versus pH of Diphenylamine by Method
15.
E
16.
E versus pH of 3- Indoleacetic Acid
versus
by Method
17.
18.
A
68
I
70
of Diphenylamine by Method II
72
74
I
versus A of 3- Indoleacetic Acid by
Method II
76
E versus pH of Pyridine by Method
78
E
I
19.
E versus
20.
E versus pH of Quinoline by Method
I
82
21.
E versus pH of Quinoline by Method I
83
22.
E versus a of Quinoline by Method II
85
23.
E versus pH of Isoquinoline by Method
24.
E versus A of
25.
E versus pH of 5- Acetyl -2,4- Dimethylpyrimidine by Method I
26.
E versus
7\
2\
of Pyridine by Method II
80
I
87
Isoquinoline by Method II
89
91
of 5- Acetyl- 2,4- Dimethylpyrimidine
by Method II
93
27.
E versus pH of 2- Aminopyridine by
I
95
28.
E versus T of 2-Aminopyridine by Method II
97
29.
E
versus pH of Benzamidine Hydrochloride
by Method I
99
30.
E versus A
Method
of Benzamidine Hydrochloride
by Method II
101
31.
E versus pH of
32.
E versus
33.
E versus pH of 4- Methylpyrimidine
34.
E versus
35.
E versus pH of m- Phenylenediamine
2\
2\
Hydrazobenzene by Method
I
104
of Hydrazobenzene by Method II
106
38.
108
113
I
E versus pH of m- Phenylenediamine
Dihydrochloride by Method
37.
I
of 4- Methylpyrimidine by Method II 110
Dihydrochloride by Method
36.
by Method
114
I
E versus '
of m- Phenylenediamine
Dihydrochloride by Method II
116
E versus pH of o- Phenylenediamine by
Method
118
I
39.
E versus
40.
E versus pH of p- Phenylenediamine by
2\
of o- Phenylenediamine by Method II 120
Method
I
122
41.
E versus h of p- Phenylenediamine by
42.
E versus pH of
43.
E versus A of Phenylhydrazine by Method II...
44.
E versus pH of
45.
E versus
46.
E versus pH of
47.
E versus A of Pyrimidine by Method II........
48.
E versus pH of p ®Aminobenzoic
T
by Method
49.
Method II 124
Phenylhydrazine by Method I... 126
128
Phthalic Acid by Method I..... 130
of Phthalic Acid by Method II..... 132
Pyrimidine by Method I........ 134
136
Acid
............................... 140
I ...
E versus pH of p- Aminobenzoic
Acid
by Method I.....................
.o...
141
E versus A of p- Aminobenzoic Acid
by Method II .. .........................c.....
143
51.
E versus pH of m- Aminophenol by Method I......
145
52.
E versus A of m- Aminophenol by
147
53.
E versus pH of o-Aminophenol
54.
E versus A of o-
Aminophenol by Method II.....
151,
55.
E versus pH of p- Aminophenol by Method I,,,..,
154
56.
E versus A
156
57.
E versus pH of
58.
E
59.
E versus
60.
E versus pH of Nicotinic Acid by Method I....
61.
E versus A of
62.
E versus pH of
63.
E versus A
64.
E versus pH of 1- Histidine by
65.
E versus A
50.
.o
.
Method II
by Method I..... 149
of p- Aminophenol by Method II.....
Anthranilic Acid by Method I.. 159
versus pH of Anthranilic Acid by Method I.. 160
\
of Anthranilic Acid by Method II
162
164
Nicotinic Acid by Method II.... 166
Sulphanilic Acid by Method
I
of Sulphanilic Acid by Method II..
168
17C
Method I....... 172
of 1-Histidine by Method ÏI.......
174
66.
E versus pH of p- Hydroxyphenoxyacetic Acid
by Method I.... ...o...........o...o.a....aoo.. 177
67.
E versus pH of p- Hydroxyphenoxyacetic Acid
by Method I...................................
68.
E versus T of p- Hydroxyphenoxyacetic
69.
E versus pH of d1
70.
E versus A of d1- Tryptophane by Method II.....
71.
E versus pH of 1- Tyrosine by
72.
E versus A of
73.
E versus pH of
Acid
by Method II... .....o ......................... 180
by Method
74.
I
Tryptophane by Method I..... 182
1- Tyrosine by Method II.........
2
77.
-Amino- 4,6.Dich.loropyrimidine
versus A of 2-Amino- 4,6- Dichloropyrimidine
by Method II
o..
.........
192
E versus pH of 2- Amino- 4,6- Dimethylpyrimidine
by Method I...oa..a.a..o....
.. oo..
194
E versus A of 2- Amino- 4,6- Di.methylpyrimid.ine
by Method II ...... ................. ... .....
196
E
.
E versus pH of 2-Amino- 4- Methylpyrimidine
by Method I...................................
78.
E versus A
80.
198
of 2-Amino- y4- Methylpy.r.im.idine
.............. .................. 200
by Method II
79.
188
.................... ............. 190
.
76.
184
Method I....e.... 186
.
75.
178
.
E versus pH of 4,5,6- Triaminopyrimidine
by Method I .... ...............................
E versus pH of
by Method II ...
203
495,6- Triaminopyrimidine
............................... 205
LIST OF TABLES
Table
I.
II.
III.
IV.
V-
VI.
VII.
VIII.
IX.
X.
XI.
XII.
XIII.
XIV.
XV.
XVI.
Phenolo.o.. ......00.o.e.o....o...o.a...00.
4
o.o.o.....o...ó
9
Amax.' pH at Inflection Point and
Tsosbestic Point of Compounds in Group I...
18
by Method
Comparison of pKa of Compounds in Group I
I and Method II .................
21
Amax., pH at Inflection Point and
Isosbestic Point of Compounds in Group II..
25
Comparison of pKa of Compounds in Group II
by Method I and Method 11......000..00.o..
27
pH at Inflection Point and
Amax
Isosbestic Point of Compound in Group III..
34
Comparison of pKa of Compound in Group III
by Method I and Method II.................
36
Amax., pH at Inflection Point and
Isosbestic Point of Compounds in Group IV..
40
Comparison of pKa of Compounds in Group IV
by Method I and Method II.................
41
Tmax.' pH at Inflection Point and
Isosbestic Point of Compounds in Group V...
44
Comparison of pKa of Compounds in Group V
by Method I and Method II .................
45
Dissociation Constants of Acetanilide
by Method I ...............................
50
Dissociation Constants of p- Aminophenylacetic Acid by Method I ...................
52
Dissociation Constants of p- Aminophenylacetic Acid by Method II ..................
54
Dissociation Constants of Aniline
Hydrochloride by Method I.................
56
Benzoic Acid
o
XVII.
XVIII.
Dissociation Constants of Aniline
Hydrochloride by Method II ................
Dissociation Constants of Benzoic Acid
byMethod
XIX.
XX.
XXI.
XXII.
XXIII.
.ao..a...
.a.o..
.o...0
60
Dissociation Constants of Benzoic Acid
by Method II..............................
63
Dissociation Constants of N,N- Dimethylaniline by Method I.......................
65
Dissociation Constants of N,N- Dimethylaniline by Method II .................o....
67
Dissociation Constants of Diphenylamine
by Method I ............................
.
69
.
71
I..
o.
.
Dissociation Constants of Diphenylamine
by Method II..o...a..a..o..a. ....
.
XXIV.
XXV.
XXVI.
XXVII.
XXXIII.
XXIX.
XXX.
XXXI.
XXXII.
XXXIII.
58
o
e
Dissociation Constants of 3- Indoleacetic
Acid by Method I..........................
73
Dissociation Constants of 3- Indoleacetic
Acid by Method II.........................
75
Dissociation Constants of Pyridine
by Method I...........................
77
Dissociation Constants of Pyridine
by Method II ..............................
79
Dissociation Constants of Quinoline
by Method I ...........o ...................
81
Dissociation Constants of Quinoline
by Method II ..............................
84
Dissociation Constants of Isoquinoline
by Method I ...............................
86
Dissociation Constants of Isoquinoline
by Method II ..............................
88
Dissociation Constants of 5- Acetyl -2,4Dimethylpyrimidine by Method I............
90
Dissociation Constants of 5-Acetyl -2,4Dimethylpyr.imidi.ne by Method II...........
92
XXXIV.
Dissociation Constants of 2-Aminopyridine
by Method Ioo..o... .000 .o.
...o
94
Dissociation Constants of 2-Aminopyridine
by Method II... .................. .........
96
Dissociation Constants of Benzamidine
Hydrochloride by Method Io.oWa..a.a..
98
.
XXXV.
XXXVI.
XXXVII.
XXXVIII.
XL.
XLI.
XLII.
XLIII.
XLIV.
XLV.
XLVI.
o.0
Dissociation Constants of Benzamidine
Hydrochloride by Method II ................ 100
Dissociation Constants of Hydrazobenzene
by Method I
.000.o0
o
XXXIX.
o
102
o
Dissociation Constants of Hydrazobenzene
by Method II..........." ................. 105
Dissociation Constants of 4-Methylpyrimidine by Method Z
...
Dissociation Constants of 4-Methylpyrimidine by Method II ... .........o. .....
.
107
109
Dissociation Constant of m- Phenylenediamine Dihydrochloride by Method I....... 111
Dissociation Constants of m- Phenylenediamine Dihydrochloride by Method II...
Dissociation Constants of
diamine by Method I
o-
..
115
Phenylene117
Dissociation Constants of o- Phenylenediamine by Method II
119
Dissociation Constants of p- Phenylenediamine by Method I....................
121
XLVII.
Dissociation Constants of p- Phenylenediamine by Method II..
.........o. 123
XLVIII.
Dissociation Constants of Phenylhydrazine
by Method I
..
..............
....... 125
o
XLIX.
L
Dissociation Constants of Phenylhydrazine
by Method II .............................. 127
Dissociation Constants of Phthalic Acid
byMethod I............................... 129
LI.
Dissociation Constants of Phthalic Acid
by Method II....... 000.o..,.mo...00.O.e.0
131
LII.
Dissociation Constants of Pyrimidine
byMethod I............................... 133
LIII.
Dissociation Constants of Pyrimidine
by Method II ............................... 135
LIV.
Dissociation Constants of p- Aminobenzoic
Acid by Method I.m.....o..
o....00... 137
LV.
Dissociation Constants of p- Aminobenzoic
Acid by Method I..
O0ou000,0,700,,u0. 138
.
LVI.
Dissociation Constants of p- Aminobenzoic
Acid by Method Io.. .. ...o.o
oa....o.a.
139
LVII.
Dissociation Constants of p- Aminobenzoic
Acid by Method II.......
........... 142
LVIII.
Dissociation Constants of m-Aminophenol
by Method I............................... 144
LIX.
Dissociation Constants of m- Aminophenol
by Method II .............................. 146
LX.
Dissociation Constants of o-Aminophenol
by Method I.
.......... 148
LXI.
LXII,
LXIII.
LXIV.
LXV.
Dissociation Constants of o-Aminophenol
by Method II.........e........
...
150
Dissociation Constants of p- Aminophenol
by Method I ............................... 152
Dissociation Constants of p- Aminophenol
by Method II.............
..
155
Dissociation Constants of Anthranilic
Acid by Method I .............,............. 157
Dissociation Constants of Anthranilic
Acid by Method I ..........................
158
LXVI.
Dissociation Constants of Anthranilic
Acid by Method II .......................... 161
LXVII.
Dissociation Constants of Nicotinic Acid
by Method I....
... 163
LXVIII.
Dissociation Constants of Nicotinic Acid
by Method II
165
LXIX.
Dissociation Constants of Sulphanilic
Acid by Method I ......................... 167
LXX.
Dissociation Constants of Sulphanilic
Acid by Method II........................ 169
LXXI,
LXXII.
LXXIII.
LXXIV.
LXXV.
LXXVI.
LXXVII.
LXXVIII.
LXXIX.
LXXX.
LXXXI.
LXXXII.
LXXXIII.
LXXXIV.
Dissociation Constants of 1-Histidine
by Method I..............................
171
Dissociation Constants of 1-Histidine
by Method II ............................... 173
Dissociation Constants of p-Hydroxyphenoxyacetic Acid by Method I...........
175
Dissociation Constants of p- Hydroxyphenoxyacetic Acid by Method I........... 176
Dissociation Constants of p-Hydroxyphenoxyacetic Acid by Method II...o.s.
179
Dissociation Constants of di- Tryptophane
by Method i
181
Dissociation Constants of dl- Tryptophane
by Method II
183
Dissociation Constants of 1-Tyrosine
by Method i ...................... ,...... 185
Dissociation Constants of 1-Tyrosine
by Method II
187
Dissociation Constants of 2-Amino -4,6Dichloropyrimidine by Method I........... 189
Dissociation Constants of 2- Amino -4,6Dichloropyrimidine by Method II... .....
191
Dissociation Constants of 2- Amino -4,6Dimethylpyrimidine by Method I........... 193
Dissociation Constants of 2-Amino-496Dimethylpyrimidine by Method II
195
Dissociation Constants of 2-Amino -4-Methylpyrimidine by Method I ................
197
LXXXV.
LXXXVI.
LXXXVII.
Dissociation Constants of 2- Amino -4Methylpyrimidine by Method
.
199
Dissociation Constants of 4,5,6 Triaminopyrimidine by Method I.....oa.o
.
201
II
Dissociation Constants of 4,5,6 Triaminopyrim.idine by Method II...
204
A STUDY OF THE LIMITATIONS OF
ULTRAVIOLET SPECTRAL DATA FOR THE
DETERMINATION OF DISSOCIATION CONSTANTS
OF ORGANIC NITROGENEOUS BASES
INTRODUCTION
Interest in the possibilities of employing ultraviolet spectral data as
a
means of determining dissocia-
tion constants of certain organic acids and bases stems
from the early work of Stenström and Reinhard
(36)
who
reported the influence of the pH upon the ultraviolet
absorption spectra of certain cyclic compounds.
This approach appeared to be especially attractive
due to the great sensitivity of organic compounds to
ultraviolet radiation which would allow these determinations to be made at high dilution.
This provides the
only means of measuring dissociation constants for those
fairly insoluble compounds which absorb energy in the
ultraviolet and whose chromophores are either protonable
or are conjugated with either acid and /or basic group.
In 1926 Stenström and Goldsmith
(37)
described
a
method for the determination of the dissociation constants of phenol and tyrosine based on observations of
Stenström and Reinhard (36) using extinction data taken
at a given wavelength in the ultraviolet over a span of
pH values ranging from pH 4 to pH 13.
The selection of
the given wavelength for this determination was based on
2
ease with which the change in extinction coefficient with
pH could be most readily followed.
Their procedure was based on the assumption that for
certain compounds two forms of absorbing species existed,
one in acidic medium, and the other in basic medium,
each
of which was capable of yielding its own absorption curve
in the ultraviolet.
Thus at
a
given wavelength there
should be a significant difference between the extinction
coefficients of the two structures taken at a fixed pH.
It was also assumed that a mixture of two types of ab-
sorbing units coexisting at
given pH would have an
a
extinction coefficient lying between those two values
and that the relationship between them would be
x(l,
where
a
=v
a)
+ ya = E
= fraction of tyrosine molecules
ionized at
the hydroxyl group
1 -a
= fraction of tyrosine molecule not ionized at
hydroxyl group
x = extinction coefficient of molecules not
ionized at hydroxyl group
y = extinction coefficient of molecules
ionized
at hydroxyl group
E
=
extinction coefficient for
two species
c =
original concentration
a
mixture of the
3
K
Since
a
= dissociation constant
[111
KlY
ffi
LL
.
anion
= K
I
J
a
K
a _
[H1
and
[acid]
x ac = Ka x c(1-a)
!
Where
a
E =
[
a
+ Ka
[[H
+ Ka
Ka_
_
Ka `
and
Ka
+y
vi.i11-114,
¡(Y - É-
`H4-"
+
eq.
(1)
[11+1
The dissociation constant could be calculated when
x and y are known and the value of E lying between x and
y has been determined for a certain pH.
To determine a value of K
a
one constructs the entire
curve showing relationship of pH and extinction coefficient at a selected and given wavelength.
For example, in the case of phenol
(37)
with meas-
urements taken at wavelength 2825Á one obtains the data
shown in Table
a
To calculate the dissociation constant,
I.
point of the curve was used for which E was approxi-
mately the arithmetical mean of the highest value
the lowest value
x = 380,
(x)
of the extinction coefficient.
y = 2822, E =
Calculated value of K
pK a
= 9.86
(y)
a
1600, pH = 9.86
= 1.38 x 10
-1 0
.
and
4
Table
Phenol:
I.
Figure
1
.2\
Extinction
Coefficient
pH
4.5
= 2825 A
pH
Extinction
Coefficient
380
9.95 to 9.8
1550
380
10.0 to 10.1
1830
7.5
435
10 ±
2100 approx.
8..75
540
10.15 to 10.2
2125
8.9
610
10,2
2160
600
10.45
2465
6
approx.
8.95 ±
C
.05
9,25
790 approx. 11.
9.3
690
11.7 ± .05
2800
9.3
755
12.75
2822
9.5
1215
13
2970
In 1935 Flexser and co-- workers
2630
(13)
published a
second procedure based on the use of ultraviolet spectroscopic data for the determination of dissociation constants of very weak bases having chromophoric groups.
The determination of dissociation constants by the
first procedure had been based on observation of changes
in the extinction coefficient at a selected wavelength
caused by variations
in
pH of the solution.
This new
approach was based on data obtained by taking the spectral
transmission curve in the ultraviolet of
a
0.1N, basic
pH.
and
in
a
a
0.1
N.
acidic,
buffered solution at an appropriate
5
2,800
2,400
2,000
E
1,600
1,200
800
400
pH
Figure
1.
Dissociation of phenol by method of
Stenström and Goldsmith (37).
Full curve experimental, broken curve
theoretical..
= 2825 A
T,
6
The calculation of acid or base strength was made as
The extinction coefficient k for
follows.
given wave-
a
length was obtained by Beer's law.
k = -log T /cl
eq.
(2)
where T = absorbancy or optical density
1
= length of cell
c =
(normally
1
cm. width)
concentration of the sample in mole /liter.
If a solute exists in two forms, say B and
Be,
so that
the total concentration c is equal to the sum of the con-
centrations of these two forms,
therefore
and if,
c =
cB + cBH+
eq.
as seems generally to be the case,
(3)
each substance
absorbs independently of the presence of the other, then
-log T = (kBcB + kB.+cBH +)1
and it follows from equations
(2),
(cBH+)/(cB) =
(k-
(3),
and
eq.
(4)
kB)/(kBH+
k)
(4)
that
o
eq.
(5)
In a dilute aqueous solution, kB may be determined by
reducing the acidity to the point where the concentration
of BH+ is vanishingly small; kB
the acidity.
Knowing these,
a
similarly by increasing
measurement of k in some
solution of intermediate acidity permits the calculation
of
cBH +
/cB and from this,
if the pH of the solution is
known, of the dissociation constant of the base.
The
modifications of the above considerations, necessary if
the dissociation constant of
a
weak acid HA which
7
and A- is to be measured, are obvious.
ionizes to H
In
the measurement of the strengths of very weak bases in
strong sulfuric acid solutions, certain complications
arise from the fact that the change of acidity involves
necessarily
a
significant change in the nature of the
medium with
a
concomitant change in the absorption
spectrum.
Measurements in Dilute Aqueous Solution
The absorption
The Acid Strength of Benzoic Acid.
of benzoic acid was determined in the following solvents:
(1)
0.1 Nosulfuric acid;
(2)
buffer containing
a
0.10 M.sodium acetate and 0.35 Mo acetic acid
(this sol-
vent is transparent in most of the range of wavelengths
available);
(3)
0.1 M.sodium hydroxide.
The results
are plotted in Figure 2, and the extinction coefficients
are given in Table II.
The logarithmic dissociation constant pKa was cala
culated by the equation
p.K.HE3
=
pKHA + log cA-/cHA
-
log
derived from substitution of equation
(k-kHB)/(ka._-k)
(5)
eq.
(6)
eq.
(7)
in the
equation
PEHB
=
PKHA
+ log
cA_.
-
log ca../cHE
which is an obvious combination and transformation of
8
3.80
3.40
3.00
2.60
log E
2.20
1.80
3
1.40
2900
I
1
2800
I
I
2700
1
)\
Figure
2.
1
1
2600
I
2500
I
I
2400
(A)
Dissociation of benzoic acid as an acid
by method of Flexser et a1. (13):
Curve 1, 0.1N.H2SO4; curve 2, buffer;
curve 3, 0.1N.Na0H.
I
2300
9
Table II
Benzoic Acid.
Extinction Coefficients in
Wavelength, A
0.1 N.
0.1
H2804
NaOH
M.
pKa
Buffer
2857
450
50
225
4011
2791
840
300
540
4.13
2727
950
475
680
4.10
2667
820
575
680
4.09
2609
675
620
640
2553
740
700
720
2500
1250
900
1050
4,09
2449
3050
1400
2350
4,35
2400
6450
2300
4500
4.27
2353
9200
4800
7200
4.30
-
Average 4018
f 0.09
the equilibrium expressions for the dissociation of
acetic and benzoic acids.
The subscript A refers to
acetate, and the subscript B to benzoate.
For the cal-
culations, values of kHB were taken from curve
1,
of kB. from curve 3, and those of k from curve 2.
value of pKHA was taken as 4,76.
that the quantity
those
The
This equation assumes
fA- fHB,fHAfB- is unchanged by a trans-
fer from infinite dilution to an ionic strength of
0.,1.
10
Within the precision of this assumption, therefore, the
PKHB
obtained is the value in terms of activities
referred to infinite dilution in water as the standard
state
pKim = -log aH
eg.
(8)
Table II gives the values of pKa thus obtained at various
wavelengths, omitting those in the neighborhood of the
isobestic point, the point where all three curves meet.
The average value of 4.16 thus obtained is in satisfac-
tory agreement with the value of 4.20 found in the recent
measurements by the conductivity method of Brockman and
Kilpatrick
(7)
and of Saxton and Meier
(33).
The conclusion of Flexser and co- workers
(13)
that
ultraviolet colorimetry cannot be applied to the measurement of the dissociation of benzoic acid was apparently
due to the limitations of their measurements.
They did
not determine the complete absorption spectra of benzoic
acid but instead measured the wavelengths at which benzoic acid has an extinction coefficient of 800
(log k = 2.9).
They thereby determined three points of
the curve for benzoate ion and three for molecular ben-
zoic acid.
Four of these six points happen to fall on
the isobestic point where of course no change takes
place.
The other two points are not in agreement with
our measurements,
11
The significant difference between the two methods
is
in the selection of the pH which is used in the
determination of the dissociation constants.
Fl.exser et al. used a pH which would give the arith-
metic mean of the extinction coefficient of the acidic
and basic solutions.
Stenström and Goldsmith used the
pH at the inflection point of
a
curve obtained by plot-
ting the pH versus the extinction coefficient.
The determination of
a
dissociation constant of
a
protonated chromophore of an organic compound depends
upon securing accurate data
(a)
in regard to the extinc-
tion coefficients of the protonated and deprotonated
species, and
(b)
the assumption that the absorption of
a
With this
mixture of the two species are additive.
information it is possible to calculate the ratio of two
species knowing the extinction coefficients of the two
forms and its mixture at
given wavelength together with
a
the pH of the mixture of two species, provided these
measurements are taken at
spectra.
a
meaningful region of the
In our work this method will be referred to as
Method II.
In Figure
3
is
an example of a typical illustration
of spectral transmission
curves of
a
simple protonated,
deprotonated chromophore, together with
mixture of the two species.
a
spectrum of
a
Absorbancy (Optical Density
,J
!'
3
/
/
'
,
/
i
'
/'
\
-'
`\
.
`\
\
2
.
.
.
.`
i
`.
I
;
`. `.
.
1`
1
,
2
-
3
\`2
3
l
210
I
I
230
220
I
I
I
240
2\
Figure
3.
I
I
250
I
260
(n)
A Typical Spectral Transmission Curve,
(1)
(2)
(3)
a
a
a
protonated or deprotonated. chromophore
deprotonated or protonated chromophore
mixture of the two species
270
280
13
It is obvious that no determination of dissociation
constants in this case
(Figure
3)
can be obtained with
measurements taken at the isosbestic points or close
proximity to wavelengths 225, 250, and 275 mµ.
Further-
more, the data in region 250 to 275 mµ would not be very
reliable due to the similarity in absorption characteristics of both species in this range.
At
7\
max.
240
mp,
one finds the greatest deviation
in extinction coefficients between the two species and
consequently in the region 235 --245
one obtains the
mi,
most accurate data for dissociation constant measurements,
On the other hand if one plots the extinction co-
efficients at wavelength 240
mp.
(the most sensitive point
of the spectra to pH changes) versus acidity over the
entire pH range, one would obtain
a
potentiometric titration curve) with
point.
curve (similar to
a
typical inflection
From this data one can calculate the dissociation
constant of the compound.
referred to as Method
In our work this will be
I.
If the compound plotted in Figure
3
had two reactive
sites in its chromophoric group then one might obtain
two inflection points indicative of two distinct dis-
sociation constants.
However, if two dissociation constants should be
indicated from the plot of pH versus extinction
14
coefficients it is evident that three distinct species
of the molecule must have been involved as the pH changes
from
C
to 14.
In this case the measurement of dissociation con-
stant from extinction coefficients of the protonated,
deprotonated, partially protonated at a given wavelength
together with pH of the partially protonated form
(Method II) would be suspect.
It is possible that more
than two species of the molecule could have been involved
in absorbance measurements
and hence calculations would
only lead to approximate values for dissociation constants for compounds having more than
a
single reactive
site in the chromophore.
When Method
I
is used in
conjunction with Method 71,
it should be possible to obtain the highest degree of
precision for
a
spectral method.
For example,
it
is
possible to determine the number of protonated and de-
protonated forms of a given molecule that are responsible
for the absorption at a given wavelength,
technique of Method
I.
using the
If results of such an investiga-
tion indicate that only two forms are responsible for the
absorption at a given wavelength,
and if the differences
in the magnitude of the extinction coefficients of these
forms are significant, then the technique of Method II
should lead to the measurement of dissociation constants
15
with greatest precision.
However, the data in Table IV
does not substantiate this hypothesis; apparently the
differences due to possible presence of
a
third molecular
species, where so indicated, are so minimal as to be
negligible in most cases.
In order to accurately determine the dissociation
constants of compounds having chromophoric groups with
two protonatable sites using Method II,
it would be
necessary to obtain the spectral transmission curve of
the half protonated chromophore.
If both sites are
weakly acidic or strongly acidic, it would be difficult
to distinguish between constants due to difficulty of
obtaining the extinction coefficient of the half protonated form.
However,
and the other strongly
if one site was weakly acidic
basic
(i.e., p- aminophenol),
one
should be able to secure more reliable measurements..
Another indication of the accuracy of these measurements is the magnitude of the differences in extinction
coefficients taken at the most favorable region of the
spectra.
These differences will be indicated on the
following tables of data.
One would assume from the work of Flexser that cal-
culations of pKa from ultraviolet data for compounds
having several
7\
max.
values in ultraviolet spectra of
the protonated and unprotonated form would yield the
16
same values of pKa as determined over the entire range
of the usable spectra.
This has never been established
experimentally and furthermore should be questionable in
the case of compounds having more than one reactive site
in the chromophore.
The procedure of Stenström and Goldsmith, on the
other hand, which was based on the measurement of changes
in extinction coefficient at an easily followed wave-
length over the entire pH range, should give
as
illustrated in Figure
single reactive site.
1
a
curve such
for simple compound with a
The behavior of compounds having
more than one reactive site has not been investigated.
For these reasons a study of the limitations and
other aspects of the use of ultraviolet absorption data
for the determination of dissociation constants of
organic bases was undertaken.
17
RESULTS AND DISCUSSION
Using these procedures,
acids and bases
a
group of simple organic
(having only one reactive site in the
chromophore) were studied.
The spectral transmission
curves of both the protonated and deprotonated form were
determined to ascertain the
extinction coefficients.
T
max.
and their respective
Having determined the
A
maxo
values of both forms, the extinction coefficients were
calculated and plotted over the entire pH range for each
value of
A
This gave an inflection point which in
max.
turn provided the pH used to calculate the dissociation
constant as described for Method
I.
For Method II the pH of the curve which gave approx-
imately the arithmetical mean of the optical density of
the protonated or deprotonated form, at a wavelength at
which
a
significant difference in extinction coefficient
values occurred
(usually at
A
max.
value of either form),
was used in the calculations of dissociation constants.
In Table III are tabulated the results of these
studies.
In general there was very
little change in
A
max.
values at pH's seven, thirteen and fourteen as would be
expected for
a
moderately weak organic base.
Moreover,
the pH of the inflection points was the same for all
wavelengths at
A
max.
values exhibited by the compound
Table III.
pH at Inflection Point and isosbestic Point of Compounds
in Group I (having one reactive site in the chromophore).
)\max.,
Compound
pH
Acetanilide
238
-
pH
pH 13
pH 14
Inflection Point
pH
max.
238
238
238
238
0.20
230
280
230
280
230
280
230
280
4.70
4.70
Benzoic Acid 230
273
224
270 sh
224
270 sh
224
270 sh
230
270
4.15
4.15
Diphenyl-
279
279
214
279
218
279
279
0.90
217
275
219
280
219
280
219
280
219
13.10
Isoquinoline 226
215
215
218
215
5.30
N,N-Dimethylaniline
242.5
285 sh
214
242.5
288 sh
218
242.5
288 sh
242.5
5.06
Aniline
1
7
amine
3- Indole-
acetic
Acid
-
Isosbestic
Point
222
241
307
Table
iii. (Continued)
Compound
p- Aminophenyl
Acetic Acid
Pyridine
pH
1
-
250 sh
255
pH
pH 13
pH 14
Inflection Point Isosbestic
A
pH
Point
max.
236
285
236
285
236
285
236
285
5.00
5.00
244 sh
250
244 sh
249
255
262
224
228
275
312.5
244 sh
249
255
262
249.5
255
262
5.00
5.10
5.15
224
228 sh
275
312.5
224
232
275
312.5
4.90
4.80
4.80
4.80
7
255
262
Quinoline
232
312.5
224
228 sh
312.5
228
243
289
20
in both acid and basic media.
The extremely weak bases, diphenylamine and acet-
anilide, gave inflection points at the expected level.
The graphical data for the determination of the inflec-
tion point of acetanilide was not clear -cut.
There was
considerable fluctuation in E value in ranging from pH 4
Since acetanilide should be an extremely weak
to pH 14.
base the inflection point at approximately pH 0.2 could
be meaningful.
The second inflection point at about
pH 4 may be due to aniline resulting from hydrolysis of
the amide.
Having established the pH of the inflection point,
the dissociation constants were then calculated by
Method
I
at wavelengths of the A
and basic regions.
max.
values in the acid
Moreover, the pH of the solution
whose spectral transmission curve gave an approximate
mean value for extinction coefficient at the "max. value
max.
either of the protonated or deprotonated form of the
compounds, was used to calculate the dissociation constants by Method II.
The results of these studies are tabulated in
Table IV.
In all cases there was reasonably good agreement
between the pKa values as determined by other methods
and the ultraviolet spectral methods using either
Table IV.
Comparison of pKa of Compounds in Group
and Method II.
Method
pH
I
I
Compound
pKa from
literature
Amax.
Acetanilide
0.61(9)
238
1
7
13
14
0.16
Aniline
4.580(18)
4.60C(32)
230
280
-
7
13
13
14
14
4.62
4.65
Benzoic Acid 4.18P(24)
4.20C(7)
224
230
270
-
7
-
13
14
1
-
-
1
7sh 13sh 14sh 4.26
218
279
-
-
1
7
13
13
14
14
219
275
280
1
7
13
14 13.12
1
-
-
-
-
7
13
14
Diphenylamine
3- Indole-
acetic Acid
0.85P(18)
7
by Method
pKa
-
4.18
-
0.88
-
-2`max.
I
Method II
pKa-pH 7 pKa-pH
230
280
4.77
4.66
4.71
4.59
225
230
270
4.23
4.16
4.28
4.19
220
279
1.33
1.35
1.34
1.35
219
275
280
4.11
4.49
-
-
-
13
Table IV.
(Continued)
Compound
pKa from
literature
Isoquinoline
5.40P(30)
Method
pH
Tmax
215
226
Method II
pKa Tmax. pKa -pH 7 pKa -pH 13
I
5.06
215
5.01
242.5 5.03
5.04
5.07
14
14
5.00
5.03
236
285
5.04
5.03
5.05
5.04
13
13
13
14
14
14
5.05
5.12
5.16
249.5 5.32
255
5.38
262
5.36
5.32
5.39
5.37
13
13
13
14
4.83
4.80
4.89
4.77
224
235
275
312.5
4.78
4.82
4.79
4.84
4.91
4.82
4.82
4.84
13
14
-
-
-
N,N- Dimethyl- 5.06C(18)
aniline
214
242.5 -
-
13
13
14
14
p-Aminophenylacetic
Acid
236
285
-
7
13
13
1
7
1
7
-
7
224
232
1
275
1
312.5 1
7
Pyridine
Quinoline
249.5
5.16S(19)
255
5.16P(2)
5.23P(2)(15) 262
4.93S(3)
7
7
7
215
225
5.33
5.42
7
1
7
5.33
5.33
5.44
-
-
14
14
23
Method
I
or Method II.
ment between
ferent
Amax.
(a)
Furthermore, there is good agree-
the pK values as determined at the dif-
values of
given compound and
a
(b)
calcula-
tions using Method II based on species existing either
at pH
7
and pH 13
(same specie).
The case of diphenylamine is one in which there is
some deviation between the two methods.
This compound
would appear to have two absorption peaks so close to
one another as to be unresolvable by the spectrometer.
If this were the case the À
max.
value that we would see
would be proportioned somewhat differently (more blunt)
than the usual absorption peak in the ultraviolet.
This
would lead less precise dissociation constant as calculated by Method II.
The dissociation constants of 3- indoleacetic acid
as determined by Method
I
appear reasonable in contrast
to the unlikely values obtained by Method II.
However,
the spectra in the region of 220 mµ was such as to make
this determination questionable.
Compounds having two protonatable sites on the
chromophore could exhibit two dissociation constants,
the magnitude of which would be dependent on the acidity
of the protonated function.
Thus within
a
given chroma
phonic group there could exist both strong and weak
acidic functions or
a
combination of both.
24
Method II, however, would not be capable of yielding
both constants unless a given compound had more than one
absorption peak each whose existence was dependent on
a
different dissociation constant, and provided it was
possible to measure the distinction coefficient of the
half protonated chromoohoric group.
only give
Otherwise it will
single value which might be only an approx-
a
imation for the dissociation constant.
However, it may
be possible to determine both dissociation constants
using Method
I.
In the case of compounds having only
strongly acidic functions (protonated form) the deproto-
nated form (weak base) would be expected to exhibit the
same structure at pH
7
through pH 13.
If this were the case,
the solutions should give
the same absorption over this pH range if no other re-
actions occurred as a consequence of the basicity.
To
test this hypothesis the spectral transmission data in
the range 210 to 320
mil
of a number of nitrogenous bases
having two weakly basic functions
(protonated function
would be strongly acidic) were obtained in which the pH
varied from one to fourteen.
The results of these
studies are tabulated in Tables V and VI.
It is
apparent from Table VI that practically all
the compounds having two reactive weakly basic functions
remain unaltered
in aqueous
solution as judged by
A
max
Table V.
Amax . pH at Inflection Point and Iscsbestic Point of Compounds in Group
TI (having two similar reactive sites in the chromophore).
Compound
pH
5-Acetyl -2,4-
223
Dimethylpyrimidine(16)
1
pH
7
233.5
pH 13
pH 14
233.5
234
252sh
Inflection Point
pH
Amax.
223
233.5
1.70
Isosbestic
Point
253
13.50
13.50
2-Aminopyridine
228
299
228
289
228
287
228
287
228
287
6.70
6.70
280
284
Benzamidine
Hydrochloride
228
228
228
228
228
11.30
245
270
Hydrazobenzene
245
239
213
318b
290b
318b
239sh
318b
318b
213
239
245
290
318
0.90
2.30
1.65
1.80
242
242
242
242
2.30
2.35
4- Methylpyrimidine(14).
244
244
245
8.88
8.40
8.80
8.75
13.10
267.5
Table V.
(Continued)
Compound
pH
m- Phenylene=
240b
diamine
Dihydrochloride
1
-
pH
pH 13
pH 14
210
240sh
290
212
219
235sh
290
235sh
290
7
Inflection Point
Amax.
pH
Isosbestic
Point
210
235sh
240
290
4.80
4.90
4.90
4.85
13.00
2.25
2.25
2.20
13.50
o-Phenylenediamine
230
280
206
213
230sh
290
230sh
290
218
238sh
290
230
290
0.75
0.75
4.25
4.20
p-Phenylenediamine
240
240
213
240
305
218
240
305
240
305
305
2.68
2.60
6.10
5.80
270
230sh
274
230
270sh
230
285sh
230
274
6.20
5.30
7.50
10.50 13.10
203
229
225sh
275sm
216
220
275sm
216
229
275
2.85
2.85
3.00
5.30
5.30
5.20
12.20
275sm
242
242
242
242
1.40
Phenylhydrazine
Phthalic Acid
221
275sm
Pyrimidine(14)
242
233
270
292
221
266
Table VI.
Comparison of pKa of Compounds in Group II by Method
and Method II.
Compound
pKa from
Tmax.
literature
5- Acetyl -2,4-
dimethylpyrimidine(16)
2-Aminopyridine
Benzamidine
hydrochloride
6.86P(2)
(6)
Method I
pKa
pKa2
pH
pKa3
I
Method II
pKa-pH 7 pKa-pH 13
1
223
233.5
1
-
-
-
7
13
14 1.56
228
287
1
7
7
13
13
14 6.62
-
228
1
7
13
14 11.32
213
239
245
290
318
-
-
13
7
1
1
7b
-
-
242
244
-
7
1
-
-
-
-
13.48
13.68
-
1.75
-
1.72
-
6.76
6.51
11.60P(2)
11 .60S (29)
Hydrazobenzene
4-Methylpyri- 1.98P(2)
midine(14)
-
0.93
2.30
1.70
1.86
13 14 2.24
-
-
2.30
-
8.87 13.15
8.37
8.75
8.80
11.27
1.72
1.60
1.75
1.86
2.13
2.10
2.14
2.09
Table VI.
Compound
(Continued)
pKa from
Tmax.
literature
pH
m-Phenylene- 4.88C(26)
diamine
2.50C(32)
Dihydro5.20C(32)
chloride
210
235
240 lb
290
-
7sh
o- Phenylene- 4.37
230
290
1
1
p- Phenylene- 2.54 (9)
diamine
6.04 (9)
6.08C(26)
240
305
1
Phenylhydrazine
5.21(9)
230
274
Phthalic
Acid
2.95T(25)
5.41T(25)
diamine
Pyrimidine
(14)
(9)
4.47C(26)
1.30P(2)
Method
PKa1
e
216
229
275
1
1
242
1
7
-
-
0
13sh 14sh
I
pKa2
pKa3
Method II
7
pKá pH 13
pK pH
2.20
2.24
2.20
4.80 12.97
4.92
4.86
4.85
2.19
2.28
2.64
2.21
2.29
2.64
m
-
7
13
14
7sh
13sh 14sh
7
13
14
0.65
0.65
4.45 13.63
4.26
4.50
4.40
7
6.10
5.62
5.87
5.87
6.06
-
7
13
13
14
14
2.62
2.60
-
7sh13
14
7
-
-
6.20
5.30
7.50
10.50 13.10
-
-
13
-
-
7
13
14
2.84
3.00
3.00
5.22 12.23
5.39
5.40
7
13
14
1.43
-
-
-
-
-
5.00
5.23
4.99
5.12
1.58
1.60
29
and E values as the pH of the solutions varied from seven
to fourteen.
a T
max.
It is interesting to note the presence of
which cannot be assigned to either the completely
protonated or deprotonated chromophoric group.
This must
be due to the presence of the third species (half pro -
tonated form).
The spectral transmission curve of o- phenylene-
diamine at wavelength 205
mil
wavelength 212 mj
(pH
hydrazobenzene at wavelength
260 mµ
and p- phenylenediamine at wavelength
(pH 1.8),
5.48),
(pH 7),
phthalic acid at
233 mµ (pH 6.95) are illustrations of the effect of the
absorbance of the intermediate form.
In general those compounds whose chromophores have
two weakly basic active sites yield dissociation con-
stants by Method II, which are in approximate agreement
with one of the values obtained by Method
I
or with
literature data despite having no information on the
extinction coefficient of the half protonated compound.
This may be due to the fact that one of the protonated
forms is so acidic that the extinction coefficient at
pH
1
is a close
approximation of that half protonated
chromophore.
In the case of nitrogenous bases Method II will
yield the dissociation constant of the more acidic form
of the protonated base if the value does not fall below
a
pKa of one.
30
The only exception to this expected behavior (same
7\
and E values at pH
max.
and 13) was that of the com-
7
pound hydrazobenzene in which the weakly basic functions
are adjacent to one another.
It is apparent that the
structure of hydrazobenzene in dilute aqueous solution
of pH
7
is not the same as that of
different from that of pH
pH 13 which in turn is
1.
One must conclude that the spectral transmission
curve obtained at pH
1
represents the protonated form,
that at pH 13 the deprotonated form and that at pH 4
the composite of both forms
nated).
a
-
6
(protonated and half- proto-
Protonated hydrazobenzene therefore behaves as
relatively strong acid having at least one highly
acidic
(protonated) function.
In order to confirm this hypothesis the experiments
were undertaken with phthalic acid.
In this
case, as
would be expected, the structure of phthalic acid in dilute aqueous solution of pH
7
was not the same as that of
pH 13; moreover, the structure in dilute aqueous solution
pH
1
was not the same as that of pH 13.
The relative
changes in structure of these two compounds with pH were
very much alike.
The agreement of values of dissociation constants as
obtained from ultraviolet spectral data for compounds
having two protonable sites is not as consistent as those
31
having a single protonatable site group.
Moreover, there
are more extended regions where pK values cannot be ob-
tained by Method II.
It is interesting to note that
optical density of the compounds of Tables IV and VI
(having two reactive sites in their chromophores) was
approximately one -half the value of those having only
single reactive site in the chromophore.
a
Consequently,
the data in Table VI was the less accurate of the two.
Only
a
few of the compounds
(pyrimidine and 4-methyl-
pyrimidine) gave dissociation constants by both Methods
I
and II at all Tmax. values which were in only approxmax.
imate agreement with the literature values.
2- Aminopyridine gave dissociation constants by both
Methods
I
and II which agree approximately with litera-
ture value but not for all
7
max.
values.
The dissocia-
tion constant was not calculated by Method II at
7
max
.
228 due to small differences in extinction coefficient
values.
p- Phenylenediamine gave two dissociation constants
by Method
I
which were in fair agreement with literature
or with one another.
At one wavelength
(305 m4)
agree-
ment was obtained with the literature values by Method
II,
while at the other wavelength (240 mµ) the dissociation
constant was not calculable at pH 13.
o- Phenylenediamine gave constants by both procedures
32
which were in fair agreement with literature value.
However, Method
I
yielded two other constants, one of
which (pK 13.63) must be due to other factors.
m- Phenylenediamine gave three different dissociation
constants by Method
I,
one of which was in agreement with
dissociation constant reported earlier.
The second con-
stant was in approximate agreement with that obtained by
Method
The third constant must arise from structural
I.
changes due to other considerations.
Hydrazobenzene gave four dissociation constants as
determined by Method
I,
with poor agreement between two
constants measured at different wavelengths.
agreement was obtained between values at
7
Good
max.
290 mµ and
Method II.
5- Acetyl- 2,4- dimethylpyrimidine, however, gave only
rough agreement between values obtained by Methods
I
and II.
The phthali.c acid experiments indicated fair agree-
ment between literature values and Method
I
values.
The
values yielded by Method II at wavelength 229 mµ were
rather poor.
Method
I
The other constant (pKa 12.23) yielded by
a
must be due to other factors.
Benzamidine hydrochloride gave
a
the literature value by both methods.
fair agreement with
The difficulty is
that the pH meter can be used up to pH 11 only, in order
33
to adjust the intermediate pH for Method II.
Phenylhydrazine gave only one value by Method
that agreed with that from literature data.
I
The reasons
for other higher values were unknown.
A number of bifunctional compounds in which
(a)
the
acid or basic site was inherent in the chromophore or
conjugated with it, and
(b)
both acidic and basic func-
tions were involved in the given chromatophori.c system,
were examined.
The results of these studies are tabulated in
Tables VII and VIII.
The results of those experiments employing Method
I
gave anywhere from one to three dissociation constants
(where two were expected).
stants obtained at one
A
max.
The agreement between con-
with that of another
7
max.
of a given compound in general was reasonably good.
Sulfanilic acid gave only one dissociation constant,
that for the amino function, which was in good agreement
with the literature.
The dissociation constant for the
sulfonic acid moiety was not obtainable
(as
expected).
In the initial work p- aminobenzoic acid gave only
what appeared to be one dissociation constant, in which
the values determined at two different wavelengths
(A
max.
values) were only in approximate agreement.
This
may be due to the superimposing of one inflection point
Table VII.
7max' pH of Inflection Point and Isosbestic Point of Compounds in
Group III (having two different reactive sites in the chromophore).
Compound
pH
p- Aminobenzoic
Acid
225
1
pH
265
275b
7
pH 13
pH 14
215
265
218
265
Inflection Point
pH
7\max.
Isosbestic
Point
215
225
235
245
255
265
275
285
295
305
315
2.90
2.10
2.30
231
281
4.25
4.25
9.85
13.35
260
275
2.30
2.20
2.30
2.30
2.25
2.25
2.25
13.10
4.40
4.70
4.55
4.80
4.50
5.00
5.00
4.85
4.85
4.90
m- Aminophenol
215
270
231sh 213
281
235sh
290
218
o-Amino-
210
270
228
281
213
240
295
218
240sh
295
228
281
4.55
4.50
9.20
13.60
phenol
255
272
p- Aminophenol
218
270
231
296
212
240
312
220
240sh
231
296
5.45
5.40
9.70
9.60
13.05
222
235sh
290
312
280
Table VII.
(Continued)
Compound
pH
Anthranilic
Acid
226
pH
Inflection Point
Amax.
pH
pH 13
pH 14
270sh 310
216
240
310
220
240
310
216
220
226
240
310
2.05
2.00
3.10
2.05
2.10
4.65
5.00
5.50
4.90
4.90
Nicotinic
Acid
212.5
255sh
260
265
212.5
255
262
269
220
255sh
262
269
220
255sh
262
269
212.5
220
255
260
262
269
4.60
4.80
4.65
4.80
4.80
4.90
12.30
12.30
Sulphanilic
Acid
212.5 247.5
250b
247.5
247.5
247.5
3.20
1
7
240
Isosbestic
Point
12.85
13.00
12.85
227
247
270
211
223
Table VIII.
Comparison of pKa of Compound in Group III (having two different
reactive sites in the chromophore) by Method i and Method II.
Compound
pK from
literature
p- Amino-
2.29S(27)
4.86S(27)
benzoic
Acid
max.
215
225
235
245
255
265
275
285
295
305
315
Method I
pK a
pH
e
2.90
2.13
2.30
Method II
pKa -pH 7 pKa -pH 13
-
13
-
-
-
7
13
14
lb -
-
-
-
-
-
2.32
2.21
2.29
2.31
2.25
2.26
2.25
-
-
4.23
4.27
9.82 13.41
4.26
4.46
1
-
-
-
-
13.08
4.38
4.65
4.56
4.77
4.50
5.00
4.99
4.85
4.86
4.92
2.96
3.06
-
-
2.92
-
-
3.10
-
2.92
-
m-Aminophenol
4.17C(26)
9.87C(26)
231
281
-
7sh
o-Aminophenol
4.72C(26)
9.71C(26)
228
281
-
7
7
-
-
4.50
4.42
9.28 13.78
-
4.46
4.51
4.43
4.41
p-Aminophenol
5.50C(26)
10.3OC(26)
231
296
0
7
7
-
-
5.42
5.38
9.70 13.00
9.57
5.45
5.54
-
7
Table VIII.
(Continued)
Method
Compound
pKa from
literature
T
Anthranilic
Acid
2.05T(25)
4.95T(25)
6.46C(22)
2.14S(27)
4.80S(27)
216
220
226
-
240
310
2.07P(17)
4.81P(17)
2.09S(20)
4.78S(20)
2.09S(12)
4.75S(12)
212
220
255
260
262
269
5
3.23C(28)
247
5
Nicotinic
Acid
Sulphanilic
Acid
max.
Method II
pKa -pH 7 pKa -pH 13
I
pH
m
13
-
-
14
-
7
13
13
14
14
1
7
-
-
lsh
7
1
7
-
2.04
1.99
3.04
2.05
2.10
4.63 12.85
4.96 12.97
5.58 12.85
4.87
4.90
1
-
-
7
7
4.49 12.22
4.74 12.30
13sh 14sh 4.71
4.92
13
4.83
14
13
4.80
14
-
7
13
-
-
13
14
14
3.17
e
-
-
-
4.70
4.55
4.76
4.59
4.65
4.95
4.73
4.70
4.82
4.79
4.73
4.84
-
3.13
-
-
3.13
38
on another in the cases where dissociation constants
were of approximately the same magnitude.
For this reason the relationship of pH versus
extinction coefficients were determined at 10
over the range 215 to 315 mµ.
m1,1
intervals
A plot of this data was
much more informative, showing that indeed there were
two dissociation constants of approximately the same
magnitude, as well as
a
third dissociation of a very
weakly acidic function.
All three of the aminophenols gave three dissociation constants by Method I, as determined using one of
the wavelengths of
7
max.
at pH 7, while the other wave
length of the second Amax value at pH
max.
7
-
provided only
one or two dissociation constants which were in good
agreement with those obtained at the other
T
max.
value.
The reason for a third dissociation constant is not
known.
Since Method II is only capable of yielding one dis-
sociation constant value, in contrast to Method I, it
was interesting to note that the dissociation value ob-
tained by two methods were in approximate agreement.
Moreover,
this agreement of Method II values could in-
volve either the higher or lower value obtained from
Method
I,
depending upon the compound in question.
Certain amino acids having protonatable chromophores
39
were examined by Methods
I
and II, inasmuch as this was
one method by which it might be possible to determine
their respective dissociation constants.
The results of
these studies are tabulated in Tables IX and X.
Since spectral procedures can only determine dis-
sociation constants which are an integral part of chromo-
phoric groups or conjugated with it, only certain amino
acids would be responsive to this procedure.
Thus, one
may determine the dissociation constant of phenolic
group of tyrosine or protonated amino ring nitrogen of
tryptophane
or
histidine.
Using Method
I,
dissociation constants were obtained
for the chromophoric groups which are only in approximate
agreement in the case of tyrosine, although in somewhat
better agreement in the case of 1- histidine with literature values.
In both
instances other apparent constants
were indicated which are unexplainable.
The data from Method II yielded values which were
either indeterminate or in reasonably good agreement with
literature.
Although p- hydroxyphenoxyacetic acid is not
an amino acid, the dissociation of the phenolic group
should behave similarly to that of tyrosine.
Determina-
tions employing Method I, however, give two constants at
two
7
max.
values which are not in very good agreement.
Furthermore,
t
is difficult
to explain the constant
Table IX.
at Inflection Point and
7,max., pH
in Group IV
1 osbestic Point of Compounds
(Amino Acids and p- Hydroxyphenoxyacetic Acid).
?\max.
Compound
pH
1
pH
7
pH 13
pH 14
Inflection Point
pH
Isosbestic
Point
2`max
.
1- Histidine 210
210sh
215
218
210
215
5.60
9.85
9.40
13.00
13.20
12.75
p-Hydroxyphenoxyacetic
Acid
222
285
222
287
235
305
235
305
222
235
285
287
305
3.10
3.10
3.10
2.80
3.10
10.30
10.30
10.40
10.50
10.30
dl-Tryptophane
217
278
218
278
221
278
221
278
218
221
278
2.70
3.05
11.90
13.10
1- Tyrosine
222.5 222.5
274
274
240
292
240
292
222.5
240
274
292
undeterminable
9.60
9.75
13.40
undeterminable
9.80
262
294
280
Table X.
Comparison of pKa of Compounds in Group IV by Method
and Method II.
pKa from
Method
Compound
literature
Tmax.
1-Histdine
6.06,9.41T(35)
5.85,9.45T(21)
210
215
p- Hydroxy-
222
235
285
287
305
phenoxyacetic
Acid
dl- Tryptophane
1- Tyrosine
9.39,11.62P(34)
9.56,10.07S(38)
10.05S(4)
9.15,10.15P(10)
11.77,12.40P(23)
Method II
pKa -pH 13
I
pH
pKa
1
7sh
-
-
1
7
-
-
-
-
13
14
-
13
-
-
7
-
-
-
13
14
218
221
278
-
7
-
-
-
1
7
13
13
14
14
222.5
240
274
292
1
7
-
-
-
-
13
14
1
7
-
-
-
-
13
14
1
I
5.60
9.85 13.02
9.33 13.16
3.13 10.30 12.75
3.15 10.29
10.38
2.92 10.43
3.22 10.28
2.65 11.88
3.08
13.05
undeterminable
9.65
9.73
13.33
undeterminable
9.74
-
10.24
10.41
10.42
10.24
-
9.31
-
10.07
-
9.84
42
around 3.20, 2.90 which is unreasonable.
Method II, however, gives
a
series of values based
on the extinction coefficient of structure existing in
aqueous solution at pH
7
which are in approximate agree-
ment with those of the more acidic constants obtained by
Method I, while those based on structures existing at
pH 13 are incalculable.
It is interesting to note that dissociation con-
stants for these compounds as determined by Method II
were frequently incalculable or unreasonable.
Moreover,
much better agreement was obtained in those cases where
calculations were based on the extinction coefficient of
the structure existing at pH 7.
Anthranilic acid behaved in much the same manner as
p- aminobenzoic acid in that it had a similar pH profile
(pH versus extinction
coefficient) at various wavelengths
which indicated the presence of two dissociation constants in close proximity to one another.
However,
it
also gave a third constant which might arise from the
deprotonation of the amino substituent.
Nicotinic acid gave two dissociation constants, one
of which was
in approximate
agreement with published
.
data, the other so low as to be suspect.
p- Hydroxyphenoxyacetic acid gave three constants.
The first constant was of such
a
magnitude as to imply
43
that dissociation of the carboxyl function was capable
of altering the chromophoric group, thus making it pos-
sible to measure the dissociation constant using spec-
troscopic methods.
The second constant gave a reason-
able value for phenolic hydrogen.
The third constant
can only be accounted for on the possible deprotonation
of the methylene moiety of the acetic acid.
Finally, compounds having three or more active
sites associated with their chromophoric groups were
examined.
The results of these studies are tabulated in
Tables XI and XII.
In general the agreement between dissociation
con-
stants reported for other methods were not in good
agreement with values found in these studies.
4,5,6 Triaminopyrimidine, which has five protonatable sites associated with its chromophore, gave three
constants by Method
I.
One of the constants
(pKa 13.4)
must have resulted from the dissociation of the amino
substituent.
Both 2- amino -4- methylpyrimidine and 2- amino -4,6-
dimethylpyrimidine gave dissociation constants which
must have been the consequence of deprotonation of the
amino substituent.
of
a
It is interesting to note the effect
methyl substituent on the magnitude of the dis-
sociation constants.
Tale
XI..
?max., pH at Inflection Point and Isosbestic Point of Compounds in
croup V (raving three or more reactive sites in the chromophore).
max.
Compound
2
=Amino -4,6Dichloropyrimidine
pH
1
pH
7
pH 14
232
232sh
297.5
232
207
232
297.5 297
222
295
225
286
225
286
218
286
222
299
224
288
224
288
218
288
232
Inflection Point
pH
)max.
pH 13
5
Isosbestic
Point
0.96
297.5 0.40
13.50
248
280
218
222
225
286
295
4.25
4.20
4.60
4.30
4.20
12.60
13.55
13.50
227
284
218
288
299
3.60
13.80
290
210
215
277
0.85
0.85
0.85
(8)
2- Amino -4,6-
Dimethylpyrimidine
(11)
2- Amino -4-
Methylpyrimidine
-
-
3.50
(5)
4,5,6-Triaminopyrimidine(31)
216
210
267b 277
215
277
215
277
5.65
5.70
.
13.25
13.40
221
226
Table XII.
Compound
Comparison of pKa of Compounds in Group V by Method
and Method II.
pKa from
literature
2- Amino -4,6-
Dichloropyrimidine
Method I
pKa
pH
Amax.
I
232
1
297.5 -
7
7
13
13
218
222
225
286
295
-
-
-
-
7
7
13
13
14
1
-
-
224
288
299
-
7
7
13
13
14
1
-
-
-
3.45
210
215
277
-
7
-
-
-
13
13
14
14
0.88
0.87
0.87
14sh
Method II
pKa -pH7 pKa -pHl3
0.92
0.57
13.50
12.60
13.57
13.52
-
4.18
4.28
4.30
4.48
4.20
-
3.47
13.85
14
(8)
2- Amino -4,6-
4.85P(2)
Dimethylpyrimidine
(11)
2- Amino -4-
4.15P(2)
Methylpyrimidine
1
14
-
undeterminable
3.96
3.89
3.82
3.95
3.87
3.90
3.31
3.32
3.62
3.76
3.32
3.62
-
(5)
4,5,6 -Triaminopyrimidine
(31)
1.47S(29)
5.78S(29)
7
5.66
5.66
13.27
13.39
5.69
5.93
-
o
46
2- Amino -4,6- dichloropyrimidine gave essentially
the same spectral transmission curve over the entire pH
spectrum.
This no doubt accounts for the poor precision
for dissociation constants determined at two different
wavelengths.
47
EXPERIMENTAL
Preparation of Samples
All chemical reagents used in this investigation
were reagent grade.
The stock solution, in each case,
was prepared using either distilled water or 95% ethanol,
depending on the solubility of the compound under investigation.
preferable.
However, the aqueous stock solutions were
The concentration of the stock solution
ranged from 0.05 x 10 -5 to 0.5 x 10 -5 mole /ml.in order
to avoid error in weighing.
If the stock solution was
unstable a new one was prepared daily.
The working solution was pipetted out from the stock
solution into 100 ml. volumetric flask, using volumetric
pipette, then diluted with distilled water and adjusted
to the desired pH with hydrochloric
acid or sodium hy-
droxide solution of suitable concentration to avoid
dilution of the sample.
14,
From pH
0
to
2
and pH 11.5 to
either the hydrochloric acid or sodium hydroxide
solution of known normality was used in dilution, instead
of water.
In the case of benzoic acid,
each working solution
for Method II was prepared independently in 1000
ml..
volumetric flask with the concentration about 10 mg. per
liter
48
Determination of pH
The pH of the working solution was determined before
and after the spectrum was taken, using a Beckman Zero=
matie pH meter, model 9600, with glass and calomel electrodes.
Accuracy is 0.1 pH and reproducibility 0.02 pH.
The original and final pH of each working solution were
determined at about ten minute intervals.
The reported
pH was the average of the above.
Determination of Spectra
The ultraviolet absorption spectra of the compound
being investigated were taken with
a
Cary 15 spectro-
photometer and recorded on the chart paper.
The instru-
ment was set for sensitivity at 4 and dynode voltage at
2
all through the course of study.
No.
and 8, which corresponded to
7
sion.
5
mp.
per chart divi-
Matched silica cells No. 1242
(1
cm. width) with
polystyrene cell- covers were used.
maintained between 20 ° -25
Scanning from 320
cases;
Chart gears were
mp.
The temperature was
°C.
to 200
mil
was done in most
except when the base line was too high, scanning
from 360
mpg,
to 200
two minutes to scan
mil
was made instead.
It took about
each sample.
For Method I, spectra of the compound were recorded
at various pH from 0 to 14, with about 0.5 pH scale
49
interval.
pH
1,
7,
On the other hand,
spectra of the compound at
and 13 were taken for Method II.
Besides, the
spectrum (of the intermediate pH) which lay between
those of pH
1
and
7
and 13 or between
1
and 13 were also
recorded.
In the case of benzoic acid and pyridine, the inter-
mediate pH values were obtained by adding half equivalent
of sodium hydroxide or hydrochloric acid solution respec-
tively.
All others were by adjustment to the desired
intermediate pH (which corresponded to the pH of the
inflection point yielded from Method I).
50
Table XIII.
Dissociation Constants of Acetanilide
by Method I.
No.
pH
E at
238
1
0.00
lA
6
0.25
0.65
1.25
1.98
2.85
3.58
7
4.30
8
5.06
5.60
6.24
7.00
7.45
7.98
8.44
8.82
9.44
9.91
10.47
11.00
11.50
12.00
12.50
13.00
13.50
14.00
2
3
4
5
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
= 238 mµ,
y = 10770,
x = 10520,
pH - 0.20,
mil
10516
10699
10760
10760
10760
10729
10729
10881
10851
10942
10912
10851
10790
10912
10760
10851
10790
10820
10760
10912
10881
10912
10912
10973
10851
10881
E = 10650
pKa = 0.16
11,00
O
o
o
o
o
o
O
O
o
o
o
o
O
238 mµ
o
10,80
o
o
o
o
o
E
10,600
10,400
10,200
t
t
0
2
i
i
4
I
i
I
6
t
i
pH
Figure 4.
E
versus pH of Acetanilide by Method
i
10
8
I.
I
t
12
t
14
52
Dissociation Constants of p- Aminophenylacetic Acid by Method I.
Table XIV.
No.
pH
E at
236 mµ
E at
285 mµ
1
0.15
0.57
0.95
1.50
2.00
2.50
3.00
3.45
3.75
4.05
4.32
4.59
4.95
5.30
5.55
5.75
5.98
303
303
329
303
329
379
480
859
1213
1643
2249
2982
4296
6015
7076
7708
8188
6.50
7.03
7.60
7.95
8.45
9.11
9.45
10.00
10.56
10.95
11.50
12.00
12.50
13.00
13.50
14.00
8971
9275
9199
9148
9148
9123
9174
9224
9224
9224
9199
9300
9199
9325
9426
9856
177
202
202
202
202
202
202
253
303
379
455
556
758
986
1137
1264
1289
1390
1440
1415
1390
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
2\
= 236 mµ,
x = 300,
1390
1390
1390
1415
1390
1390
1415
1390
1415
1440
1415
1440
E = 4800
y = 9300,
pH = 5.00, pKa = 5.00
= 285 mµ,
y = 1450,
x = 200,
E = 800
pH = 5.00, pKa = 5.03
2\
10,000
236 mµ
,000
6,000
E
4,000
2,00
0
Figure
2
5.
4
6
8
10
pH
E versus pH of p- Aminophenylacetic Acid by Method
12
14
ui
w
I.
54
Table XV.
À
(mO
Dissociation Constants of p- Aminophenylacetic Acid by Method II.
E at
pH 1.00
200
205
210
215
220
225
230
235
236
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
0
6697
6065
3285
1112
505
354
354
354
354
354
354
354
329
278
253
253
237
202
152
101
76
76
51
25
0
pH 7.04
E at
pH 5.10
E
pKa
20596
11625
6065
4625
4094
4069
4675
5105
5080
4625
3311
1946
1011
632
-
556
607
733
834
859
809
581
354
202
126
31590
15921
5812
3993
4599
6192
8087
9227
9119
8415
6015
3386
1643
960
783
885
1112
1365
1415
1314
1011
607
329
152
25
51
0
0
5.04
-
4.88
5.00
5.04
5.04
5.05
5.06
5.05
5.08
5.13
5.01
5.00
5.00
5.05
5.03
5.00
5.05
5.06
5.10
-
pH 13
E
pKa
5054
5206
5257
5257
5383
6596
8340
9300
9275
8415
5939
3311
1617
885
758
885
1112
1365
1440
1314
986
581
303
152
25
0
-
4.95
5.03
5.04
5.05
5.05
5.05
5.03
5.06
5.02
4.96
5.00
5.00
5.05
5.04
4.99
5.02
5.01
5.00
-
32,000
55
28,000
24,000
vpH
1.00
'pH
5.10
°pH
7.00
pH
13.00
20,000
16,000
12,000
8,000
4,000
0
200
220
240
260
280
300
2\(m11)
Figure 6.
E versus
2\
of p-Aminophenylacetic Acid
by Method II.
320
56
Table XVI.
No.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Dissociation Constants of Aniline
Hydrochloride by Method I.
pH
E at
230 mµ
0.80
1.55
2.10
2.68
3.20
3.93
4.25
4.58
5.03
5.38
5.70
6.62
7.53
8.65
9.80
11.00
12.00
13.00
14.00
E at
280 mµ
89
0
114
114
216
546
1815
3122
3845
3807
7792
7970
8147
8046
8160
8147
8338
8249
8236
8236
0
0
25
76
305
520
635
635
1320
1345
1371
1371
1383
1383
1421
1409
1396
1396
2\=230 mµ,
x=100,
E=4500,
y=8200,
pH=4.70,
pKz 4.62
T=280mµ,
x=0,
E=750,
y=1450,
pH=4.70,
pKa= 4.65
8,000
6,000
230 mµ
.
NM
E
4,000
I
2,000
280 mµ
0
1
0
2
4
I
I
I
6
8
I
I
I
pH
Figure
7
E versus pH of
Aniline Hydrochloride by Method
t
12
10
1.
t
14
58
Table XVII.
2\(mµ)
Dissociation Constants of Aniline
Hydrochloride by Method II.
E at
pH 1.17
210
1576
215
220
225
113
45
34
56
68
79
113
113
113
101
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
0
11
11
11
11
11
11
0
0
0
0
0
E at
pH 4.80
0
0
957
2984
4167
3886
2590
1363
687
394
360
439
597
732
800
732
552
282
146
56
23
0
0
pH 7.00
E
3919
4110
5518
7264
7995
6869
4482
2252
1070
563
563
709
991
1273
1374
1250
901
518
248
113
56
23
11
pH 13
pKa
-
4.77
4.69
4.68
4.65
4.63
4.58
4.69
4.59
4.63
4.68
4.66
4.66
4.61
4.74
4.65
-
pKa
E
0
0
2703
6025
7489
6588
4302
2252
1070
563
552
698
957
1227
1284
1160
800
439
191
56
23
0
0
-
4.71
4.65
4.63
4.65
4.63
4.58
4.67
4.57
4.59
4.64
4.59
4.57
4.55
4.56
-
8,000
59
7,000
o
pH
pH
4.80
pH
7.00
1.17
pH 13.00
6,000
5,000
E
4,000
3,000
2,000
1,000
0
210
230
250
270
290
7\
Figure
8.
E
versus
2\
310
(mw)
of Aniline by Method II.
330
60
Table XVIII.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Dissociation Constants of Benzoic Acid
by Method I.
pH
E at
230 mµ
0.80
1.59
2.28
3.15
3.97
4.60
4.78
6.10
7.03
7.84
8.94
10.04
11.05
12.00
13.00
14.00
11124
11043
11075
10819
9310
8266
7673
7079
7063
7223
6982
7047
7095
7095
6934
7095
E at
270 mµ
899
899
899
899
770
674
626
562
562
546
578
562
594
562
546
578
T=230 mµ,
x=7600,
E=9100,
y=10700,
pH=4.15, pK =4.18
2\=270 mµ,
x=562,
E=710,
y=900,
pH=4.15, pK =4.26
a
16,000
12,000
8,000
E
4,000
0
t
0
1
2
t
t
4
1
t
6
t
t
t
8
pH
Figure
9.
E versus pH of Benzoic Acid by Method I.
t
10
1
1
12
1
1
14
1,000
900
800
E
700
600
270 mµo
o
500
o
i
1
0
Figure 10.
2
4
6
10
8
pH
E versus pH of Benzoic Acid by Method
I.
12
i
14
63
Table XIX.
?\(mµ)
210
215
220
225
230
235
240
245
250
255
260
265
Dissociation Constants of Benzoic Acid
by Method II.
E at
3303
4663
7521
10108
11161
9702
6393
3008
1339
5355
6197
7897
8724
7822
5641
3309
1729
1038
752
692
662
662
617
300
305
310
315
320
15
15
15
15
275
280
285
290
295
at
pH 4.80
797
752
842
963
1009
978
842
526
150
30
15
270
272.5
E
pH 1.05
572
376
165
45
15
15
0
0
0
0
E
pH 7.03
pKa
5827
6421
7897
8347
7063
4848
2600
1396
915
706
626
562
562
465
417
225
32
0
0
0
0
0
0
0
4.16
-
4.23
4.16
4.10
4.16
4.22
-
pH 13
pKa
E
5415
6046
7912
8093
7010
4844
2587
1474
1023
-
752
692
647
647
526
496
271
90
45
-
15
-
0
0
0
0
0
4.28
-
-
4.19
4.10
4.20
4.10
-
4.17
4.10
4.15
4.12
-
64
12,000
10,000
'
o
pH
1.05
pH
4.80
pH
7.03
pH 13.00
8,000
E
6,000
4,000
2,000
o
210
230
250
270
290
310
(mw)
Figure 11. E versus
T
of Benzoic Acid by Method II,
330
65
Table XX.
Dissociation Constants of N,N- Dimethylaniline by Method I.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
pH
0.00
0.45
0.85
1.44
1.84
2.50
3.00
3.48
3.84
4.02
4.15
4.35
4.51
4.66
4.85
5.05
5.20
5.42
5.65
5.85
6.11
6.37
6.70
7.04
7.31
7.68
8.45
9.21
9.91
10.75
11.50
12.00
12.50
13.00
13.50
14.00
E at
242.5 mµ
471
471
471
471
471
508
659
791
1318
1902
2241
3126
3729
4991
6328
7815
8927
10810
12260
12618
14576
14896
15782
16064
15800
15725
15424
15198
15706
15989
16460
16497
16460
16422
16403
16441
2\=242.5,
x=450,
E=8500
y=15900,
pH=5.10,
pKa=5.06
c---,,---0
242.5 mµ
16,000
WO
12,000
E
8
,
000
4,000
WPM
0"
-
-1
-I
1
0
2
I
4
I
1
1
1
6
8
I
1
10
pH
Figure
12.
E versus pH of
N,N- Dimethylaniline by Method I.
1
1
12
I
I
14
67
Table XXI.
À(mµ)
Dissociation Constants of N,N- Dimethylaniline by Method II.
E at
pH 1.00
210
215
220
225
230
235
240
242.5
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
4331
471
132
151
282
320
377
414
414
414
414
320
132
94
75
94
94
94
94
94
113
113
113
94
E at
pH 7.08
pKa
pH 5.08
E
10358
4237
3277
4143
5593
7156
8286
8437
8343
7401
5650
3766
2448
14124
7439
6026
7721
10546
13371
15311
15612
15348
13446
10264
6949
4369
1695
1412
1337
1281
1149
942
791
659
527
414
282
3126
2693
2637
2373
2090
1751
1394
1130
885
697
452
-
5.01
5.02
5.03
5.05
5.04
5.03
5.03
5.02
5.02
5.02
5.04
5.00
5.03
5.06
5.10
5.04
5.03
5.06
5.02
5.01
5.01
5.05
5.03
E
7458
7646
7062
8380
11017
13936
16008
16290
16083
14124
10716
7062
4539
3258
2731
2561
2599
2166
1789
1412
1149
923
716
471
pH 13
pKa
-
5.04
5.15
5.11
5.09
5.08
5.07
5.07
5.07
5.06
5.07
5.06
5.03
5.07
5.08
5.07
5.13
5.06
5.08
5.03
5.03
5.06
5.08
5.08
16,000
® pH
1.00
d
pH
5.08
°
pH
7.08
A
pH 13.00
12,000
E
8,000
4,000
0
210
230
250
270
2.0
310
330
A (mµ)
Figure 13.
E versus
7\
of N,N- Dimethylaniline by Method II.
m
co
69
Table XXII.
Dissociation Constants of Diphenylamine
by Method I.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
T=279 mµ;
y=14300,
pH
0.00
0.20
0.40
0.57
0.76
0.90
1.06
1.27
1.35
1.59
1.82
2.00
2.25
2.62
3.00
3.50
4.00
4.57
5.05
5.48
6.10
6.57
6.99
7.60
8.20
8.95
9.65
10.30
10.95
11.50
12.00
12.50
13.00
13.50
14.00
E at
279 mµ
1358
1790
2901
4599
6296
7685
9383
11080
11574
12747
13364
13642
14012
14167
14352
14352
14352
14414
14352
14475
14383
14290
14506
14352
14444
14414
14352
14506
14537
14506
14568
14660
14568
14660
14660
x=1350,
E=8000
pH=0.90,
pKa=0.88
16,000
u
MP
n
v
O
.
v
n
279 mµ
12,000
E
8,000
4,000
i
I
2
I
I
4
I
i
i
1
6
i
i
10
8
pH
Figure 14.
E versus pH of
Diphenylamine by Method
I.
1
1
12
it
14
71
Table XXIII.
?\
(mµ)
210
215
220
225
230
235
240
245
250
255
260
265
270
275
279
280
285
290
295
300
305
310
315
320
Dissociation Constants of Diphenylamine
by Method II.
pH 1.01
E at
E at
pH 1.38
E
15123
7377
4475
3457
3086
2901
2901
3025
3488
4321
5062
5895
6821
7531
7716
7685
7253
6296
5031
3765
2469
1543
833
340
15741
8488
5864
4938
4475
4290
4136
4321
4753
5648
7037
8457
9753
10833
11204
11173
10617
9259
7407
5494
3673
2160
1173
463
16049
9043
7099
6019
5494
5093
4938
5093
5864
7284
9074
10957
12685
14043
14444
14414
13611
11759
9414
6914
4599
2778
1389
586
pH 7.00
PH 13
pKa
-
1.33
1.24
1.24
1.14
1.19
1.16
1.32
1.47
1.39
1.37
1.38
1.37
1.35
1.35
1.33
1.30
1.30
1.29
1.27
1.38
1.19
1.38
E
pKa
15741
8981
7130
6049
5494
5093
4969
5093
5895
7377
9105
10957
12747
14074
14444
14414
13673
11821
9444
6944
4630
2747
1358
586
-
1.34
1.26
1.24
1.14
1.21
1.16
1.33
1.49
1.40
1.37
1.39
1.37
1.35
1.35
1.34
1.31
1.31
1.30
1.28
1.36
1.12
1.38
16,000
G
pH
1.01
pH
pH
1.38
7.00
pH 13.00
12,000
E
8,000
4,000
o
210
i
I
230
t
t
t
I
250
t
t
t
T
Figure 15.
i
I
270
1
a
I
t
I
290
( ml-- )
E versus T of Diphenylamine by Method II.
i
I
310
t
330
73
Table XXIV.
No.
Dissociation Constants of 3- Indoleacetic
Acid by Method I.
pH
0.00
0.50
1.00
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
1.45
1.95
2.51
2.75
2.95
3.39
3.79
4.26
4.65
5.11
5.56
6.20
6.57
6.99
7.50
8.06
8.52
8.95
9.56
10.05
10.51
11.00
11.50
12.00
12.50
13.00
13.50
14.00
30
31
E at
219 mµ
32824
30998
32909
30998
32824
31847
32696
30149
32272
32484
31423
33715
30998
31762
30701
30828
32059
32654
30701
32187
32144
30488
30870
30531
32569
30786
29936
30573
33970
36858
39278
E at
280 mµ
5732
5732
5648
5648
5945
5945
5732
5435
5732
5945
5478
5732
5223
5308
5180
5180
5478
5520
5138
5393
5350
5096
5223
5138
5478
5223
5053
5180
5478
5563
5393
?\=219 mµ,
x=30200, E=34600, y=39200, pH=13.10, pKa=13.12
T=280
pKa undeterminable
m[1,
44,000
219 m
36,000
28,000
E
20,000
IMP
12,000
280 mµ
.
4,000
1
Ó
i
2
i
I
i
4
6
1
8
1
10
pH
Figure 16.
E versus pH of 3- Indoleacetic Acid by Method I.
o
.
1
12
14
75
Dissociation Constants of 3- Indoleacetic
Acid by Method. II.
Table XXV.
?\(mµ)
200
205
210
215
219
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
E
at
E at
pH 7.02
pH 1.00
pH 4.40
E
23355
20679
25605
31338
29936
28662
15711
5435
2760
2335
2335
2633
3185
3992
4671
5223
5308
5265
4416
3185
1104
19193
19448
24416
30786
31847
31210
20807
7643
3057
2251
2251
2548
3057
19278
18174
22081
28790
32527
32484
25902
10616
3397
2166
2123
2293
2803
382
85
42
0
0
3907
3609
4671
5223
5435
5520
4671
4374
5053
5308
5520
4841
4331
2208
3864
1699
594
212
85
42
0
pH 13
pKa
1019
425
212
85
0
-
4.41
4.69
4.96
4.11
4.10
4.40
4.53
4.46
4.45
4.58
4.88
4.70
4.95
-
4.23
4.24
4.33
4.70
4.63
4.87
4.41
-
pKa
E
34013
34862
36008
36263
34183
33673
26115
10616
3355
2081
2038
2251
2760
3524
4289
4926
5223
5435
4765
4246
2123
892
340
127
85
42
-
o
-
4.49
4.39
4.42
4.53
4.40
4.71
4.81
4.94
4.77
5.05
-
4.15
4.25
4.55
4.40
4.39
4.41
-
40,000
v
32,000
°
pH
1.00
pH
4.40
pH
7.00
pH 13.00
24,000
E
16,000
8,000
o
200
I
I
I
I
I
220
I
I
240
I
II
1
I
260
1
I
280
1
I
.
+
300
(ml,)
Figure 17.
E versus
r,
of
3-
Indoleacetc Acid by Method II.
4
320
77
Table XXVI.
Dissociation Constants of Pyridine
by Method I.
pH
No.
1.26
2.17
3.37
4.05
4.48
5.05
5.47
5.90
7.10
7.58
9.44
10.37
11.13
12.00
13.00
14.00
1
2
3
3A
4
5
5A
6
7
8
9
10
11
12
13
14
?\=249.5 m
,
E at
249.5 mµ
E at
255 mµ
E at
262 mµ
4757
4750
4710
4499
3912
3607
3091
2668
2527
2527
2512
2488
2512
2535
2543
2543
5407
5282
5203
4969
4296
3991
3396
2934
2739
2739
2700
2660
2700
2778
2739
2778
3443
3208
2973
2895
2504
2465
2222
1886
1800
1886
1878
1870
1878
1878
1878
1875
x=2500, E=3560, y=4760, pH=5.00, pKa=5.05
)\=255 mµ,
x=2700, E=3920, y=5200, pH=5.10, pKa=5.12
mµ,
x=1780, E=2380, y=3000, pH=5.15, pK =5.16
a
)\=262
5,600
4,800
4,000
E
3,200
255 mh
249.5 mµ
2 ,400
262
1,600
0
Figure 18.
2
4
8
6
pH
E versus pH of pyridine by Method I.
10
12
mµ.
14
J
79
Table XXVII.
T (m1)
Dissociation Constants of Pyridine
by Method II.
E at
pH 1.12
200
205
210
215
220
225
230
235
240
245
249
250
252.5
255
256.5
260
262.5
265
270
275
280
285
290
295
300
305
310
315
320
E
at
pH 5.78
3028
2551
1255
389
130
0
0
0
0
0
178
405
931
1822
3150
4534
4688
4858
5328
5182
3603
3093
1174
105
40
308
737
1377
2178
2915
3109
2955
3385
3498
2227
2219
972
105
32
24
24
16
8
0
0
0
0
32
0
0
0
0
0
0
0
0
0
0
E
pH 7.02
pK a
4089
1498
583
494
470
502
648
891
1239
1806
2348
2518
2186
2607
2834
1628
1887
972
81
0
0
0
0
0
0
0
0
0
0
-
5.27
5.36
5.32
5.35
5.38
5.38
5.38
5.42
5.36
-
pH 13
pK a
E
0
0
0
0
0
0
324
810
1255
1798
2348
2510
2186
2599
2826
1619
1878
972
81
0
0
0
0
0
0
0
0
0
0
-
5.22
5037
5.32
5.36
5,38
5,39
5.38
5.43
5.37
-
-
80
6,000
pH
'
G
5,000
1012
pH 5.78
pH 7.00
pH 13000
4,000
E
3,000
2,000
1,000
0
200
220
240
260
280
300
T (m4)
Figure 19.
E versus
2\
of Pyridine by Method II.
320
81
Table XXVIII. Dissociation Constants of Quinoline
by Method I.
pH
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
0.30
0.80
1.29
1.89
2.40
2.98
3.55
3.86
4.17
4.57
4.85
5.48
6.00
6.55
6.91
7.83
8.89
9.88
11.00
12.00
13.00
14.00
E at
224 mµ
E at
232 mµ
17892
16667
18137
17647
17647
17647
18137
18627
19265
22206
24510
29314
30294
30441
31471
31275
32010
31176
31373
31520
32353
35294
38235
36765
38333
37255
37304
37402
35784
34461
32353
27451
23284
15196
11520
10784
10784
10784
10784
10784
10784
10784
10784
11275
E at
275 mµ
312.5 mµ
1667
1569
1716
1667
1667
1716
1716
1863
2108
2353
2745
3382
3578
3578
3824
3676
3676
3627
3824
3676
3676
3627
7157
6863
7059
6912
6863
6961
6765
6569
6275
5686
5294
4314
3824
3431
3922
3725
3725
3725
3775
3725
3725
3725
E.
at
x=17400, E=25000, y=31400,
2\=232 mµ, x=10800, E=24200, y=37600,
)\=275 mµ, x=1700,
E=2600,
y=3700,
pH=4.90, pKa=4.83
2\=312.5 mv, x=3700, E=5400, y=7000,
pH=4.80, pKa=4.77
2\=224 mu,
pH=4.80, pKa=4.80
pH=4.80, pKa=4.89
a
a
40,000
o
224 mµ
32,000
24,000
E
16,000
232 mµ
8,00
0
Figure 20.
2
4
6
10
8
pH
E versus pH of Quinoline by Method
1.
12
14
0o
N
8,000
6,000
E
4,000
2,000
0
1
0
1
2
1
1
4
1
1
1
1
6
8
1
1
10
1
1
12
1
14
pH
Figure 21.
E versus pH of Quinoline by Method I.
m
84
Table XXIX.
2\(mp,)
210
215
220
224
225
228.5
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
312.5
315
320
325
330
335
340
Dissociation Constants of Quinoline
by Method II.
E at
E at
pH 1.02
pH 5.07
9559
9069
11275
17157
18627
27696
31618
35833
8823
20098
19559
882
686
637
735
833
1176
1569
2010
2647
3431
1618
1716
1716
2108
2353
2647
2892
3039
3235
3382
3382
4069
3971
4020
4902
3186
1961
1176
980
686
539
4412
5539
6373
6569
6912
6471
4167
2843
2206
1520
1078
2.2059
26029
26422
27451
26275
14902
3676
E
pH 6.98
pKa
26667
25784
28382
30539
29902
26961
22059
3137
1961
2010
2206
2451
2892
3137
3431
3578
3578
3529
3284
2794
3137
2696
2549
3725
1471
441
294
294
294
294
4.86
4.84
4.84
4.78
4.72
-
4.96
4.82
4.60
4.80
4.75
4.90
4.83
4.78
4.80
4.79
4.79
4.77
-
4.83
4.87
4.80
4.83
4.84
4.79
4.91
4.79
4.82
4.74
4.73
pH 13
E
29216
29557
30392
32108
31618
27696
23039
3088
1961
2108
2402
2598
2941
3186
3529
3627
3627
3627
3333
2843
3186
2745
2549
3725
1471
392
294
294
294
294
pKa
5.01
5.05
4.96
4.91
4.89
-
4.85
4.82
4.60
4.89
4.89
4.98
4,85
4.81
4.82
4.82
4.83
4.89
-
4.79
4.85
4.78
4.83
4.84
4.79
4.92
4.79
4.82
4.74
4.73
40,000
pH 1.02
pH 5.07
32,000
o
pH 6.98
pH 13.00
24,000
E
16,000
8,00
0
210
230
250
290
270
7
Figure 22.
(m)
E versus A of Quinoline by Method II.
310
330
350
86
Table XXX.
Dissociation Constants of Iso- Quinoline
by Method I.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
2\=215 mµ,
pH
0.43
1.01
1.51
2.01
2.44
3.13
3.60
4.15
4.71
5.28
5.69
6.50
7.00
7.66
8.58
9.13
9.81
10.52
11.03
12.00
13.00
14.00
E at
215 mµ
28788
26818
28030
28106
27348
28636
28712
29470
35606
43333
51818
61288
62045
59924
59924
62424
61061
60758
57652
60906
61136
40758
x=28000, E=44000, y=61000, pH=5.30, pKa=5.33
a
64,000
o
o
o
o
0
215
mi.;.,
o
56,000
48,000
E
40,000
32,000
o
o
24,000
'
Figure
1
0
1
2
23.
1
i
4
1
i
6
1
1
i
pH
E versus pH of Iso-quinoline by Method
1
10
8
1.
1
1
12
1
14
88
Table XXXI.
(mµ)
210
215
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
318
320
325
330
335
340
345
Dissociation Constants of Iso- Quinoline
by Method II.
E at
E at
pH 1.01
pH 5.28
21818
26894
33333
41288
37879
13258
3106
1591
1591
1742
2121
2197
2273
2273
1667
1515
1364
1364
1742
2500
3030
3788
4091
4242
4318
4394
4167
3030
34470
43409
37045
30303
23864
8333
3030
2273
2424
2652
2879
2955
2727
2576
2121
1591
1515
1591
1970
2727
3030
3409
3788
3485
2727
2879
2576
1742
1061
1515
pH 7.00
E
pKa
50000
61742
38636
14394
7500
3788
3030
5.37
5.33
3182
3333
3636
3636
3712
3561
3030
2803
1742
1742
1894
3030
2879
2727
2879
3409
2652
682
530
606
455
455
5.40
5.32
5.31
5.28
5.28
5.54
5.46
5.46
5.58
5.46
5.40
-
5.44
5.35
5.24
-
®
-
5.43
5.38
5.32
5.39
5.47
5.37
5.28
5.40
pH 13
E
61212
62045
40909
15152
6818
3712
2879
2955
3182
3561
3561
3636
3409
2803
2879
1667
1667
1591
2045
2727
2651
2727
3333
2727
833
455
455
455
455
pKa
5.60
5.33
5.30
5.42
5.37
5.25
5.58
5.28
5.24
5.28
5.23
5.23
5.46
-
5.50
5.28
5.28
-
-
5.54
5.46
5.28
5.36
5.48
5.40
5.28
5.40
64,000
89
opH
1.01
pH
pH
5,28
7.00
O
56,000
pH 13.00
48,000
40,000
E
32,000
24,000
16,000
8,000
4.
0
i
1
210
i
.
i
.
if
.
,
. .
1
.1
.-.=.--.-0;re
r
ii.
;
24.
E
i
.1
ii
,
240
270
versus
(m4)
of Iso-quinoline by Method II.
300
A
Figure
_
)\
330
360
90
Table XXXII.
Dissociation Constants of 5-Acetyl -2,4Dimethylpyrimidine by Method I.
pH
No.
E at
223
0.49
0.97
1.33
2.05
2.40
2.97
3.65
4.95
5.69
6.16
6.91
7.23
8.24
9.35
10.36
11.20
12.00
13.00
14.00
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
-N=223 mil,
7\=233.5
mil
8792
8426
8528
8305
8447
8447
8284
8284
8122
8183
8122
8345
8162
8142
8122
8081
7919
7147
4467
x=4500, E=6400, y=8200,
rku,
E at
233.5
mia,
7005
6437
7614
9868
10416
10680
10741
10741
10782
10761
10701
10802
10721
10843
10680
10680
10701
10640
10233
pH=13.50, pKa=13.48
x=7000, E=9200, y=10800, pH=1.70, pKa=1.56
x=10200, E=10400, y=10700, pH=13.50, pKa= 13.68
12,000
233.5 mµ
10,000
o
8,000
E
6,000
223 m
4,000
I
I
o
2
I
i
4
I
I
I
I
8
6
I
I
10
I
I
I
12
14
pH
Figure
25.
E
versus pH of 5-Acetyl -2,4-Dimethylloyrimidine by Method
I.
92
Table XXXIII. Dissociation Constants of 5- Acetyl 294Dimethylpyrimidine by Method II.
?\
E at
( mpa, )
pH 1.05
200
205
210
215
220
223
225
230
233
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
0
5
1005
5307
6995
8040
8322
8241
7417
6292
6030
4724
4261
4281
4281
3819
2854
1668
1065
864
764
704
603
482
422
302
201
101
E at
pH 1.67
4864
4121
4623
5910
7477
8322
8543
8683
8241
7920
6834
5688
4905
41.01
3196
1990
1085
784
663
603
543
462
362
302
241
201
100
_pH 7.04
E
pK a
7035
3618
3638
4824
6734
8040
8824
10231
10550
10493
9407
7417
5588
3920
2412
1065
583
462
362
322
241
201
141
121
101
80
40
-
1.83
1.67
1.79
-
1.64
1.76
1.75
1.80
1.76
1.75
1.71
1.67
1.77
1.70
1.60
1.73
1.85
1.91
1.94
1.94
1.93
1.85
-
pH 13
pK
E
0
0
0
0
4422
7035
8241
9970
10452
10432
9427
7437
5628
3859
2432
1065
563
442
382
342
281
221
161
141
101
60
20
a
-
-
1.68
1.72
1.79
1.76
1.76
1.73
1.90
1.76
1.70
1.62
1,76
1.82
1.,,88
1.88
1.90
1,90
1.80
-
93
14,000
12,000
v pH
1.05
pH
1167
pH
7
°
4 pH
04
13,00
10.,000
8,000
u
6,000
4,000
2,000
0
200
220
240
260
T
Figure 26.
E
versus
by Method
A
of
iI
280
300
320
(rnP,)
5- Acetyl- 2,46pimethy1pyrimid;.ne
94
Table XXXIV.
No.
pH
Dissociation Constants of 2-Aminopyridine
by Method I.
E at
228
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
1.33
2.05
3.05
3.70
4.86
5.43
6.03
6.64
7.01
7.95
9.04
9.92
10.44
10.98
12.00
13.00
14.00
mkt,
8538
8739
8903
8890
8802
8802
8852
9103
9129
9267
9329
9292
9329
9292
9017
9042
9042
E at
287 mµ
E at
292 mµ
4269
4395
4382
4420
4395
4370
4269
4093
5023
5073
5148
5148
5148
5035
4884
4357
3842
3616
3553
3528
3516
3553
3415
3528
3528
3855
3767
3754
3767
3742
3717
3642
3705
3717
E at
301
m
5525
5688
5738
5738
5650
5525
5148
3993
3039
2398
2373
2323
2285
2336
2260
2310
2336
A=228
mil,
x=8800, E=9100, y=9350,
pH=6.70,
pKa=6.62
A=287
m[1,
x=3750, E=4050, y=4400,
pH=6.70,
pKa=6.76
)\=292
m4.1,
x=3500, E=4250, y=5150,
pH=6.75,
pKa=6.75
ñ=301
mil,
x=2500, E=3750, y=5250,
pH=6.70,
pKa=6.78
228 mµ
8,000
_ ---, -+- ----- ,
6,000
11,
E
4,000
287 mµ
---
2,000
0
i
0
I
2
I
I
4
I
I
I
I
-----1------------,---301 mµ
I
8
6
292 mµ
I
10
pH
Figure 27.
E versus
pH of 2mAminopyridine by Method
10
I
I
12
I
14
96
Table XXXV.
7\
(mµ)
Dissociation Constants of 2- Aminopyri.dine
by Method 11
E at
pH 1.18
200
205
207
210
215
220
225
228
230
235
240
245
250
255
260
265
270
275
280
285
287
290
292
295
300
305
310
315
320
E at
pH 6.11
7685
1871
1557
1790
3135
5460
7887
1921
1608
1871
3236
5561
8140
9201
9120
6673
1820
8889
9100
9080
6775
2224
354
384
556
859
1274
1871
2629
3539
526
394
516
819
1244
1830
2609
3438
4449
4853
5359
5561
5986
6168
5966
5137
3953
2629
4328
4651
5051
5274
5511
5602
5298
4540
3438
2275
E
pH 7.00
pKa
a
5157
2315
2326
2831
4449
6724
8696
9151
8999
6775
3134
1112
536
607
910
1365
2022
2730
3438
4014
4146
4277
4287
4206
3842
3286
2558
1820
1122
_
-
-
6.64
-
-
6.51
6.52
6.65
6.55
6.60
6.59
6.63
6.61
6.62
E
.pH 13
pKa
a
2750
3347
3640
4146
5460
7887
10111
10566
10415
8291
4803
2123
1011
1011
1325
1871
2558
3316
3953
4307
4348
4277
4146
3832
3064
2214
1335
708
334
--
-
--
-
-
6.52
6.70
6.66
6.76
6.77
6.84
6.83
6.85
97
12,000
o pH
1.18
pH
6.11
pH
7.00
°
pH 13.00
10,000
8,000
6,000
E
4,000
1
1
1
-
[
,
`
2,000
o
1
200
.
I
220
.
I.
I
240
1
I
.
I, I,
260
(
Figure
28.
E versus T
Method I1,
I. I.
280
m4
)
of 2- Aminopyridine by
1,
300
I
320
98
Table XXXVI.
Dissociation Constants of Benzamidine
Hydrochloride by Method I.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
)\=228
mL;,,
pH
0.00
0.48
1.00
1.45
2.00
2.54
3.04
3.51
4.00
4.50
5.00
5.50
5.96
6.54
7.00
7.51
8.10
8.57
9.22
9.75
10.13
10.57
11.00
11.50
12.00
12.50
13.00
13.50
14.00
x=8850, E=9900, y=11000,
E at
228 mµ
10925
11040
11040
11012
10983
11012
11098
10925
10954
10954
10983
10983
10867
10954
11012
10896
10983
10983
10896
10751
10723
10607
10202
9682
9191
8873
8786
8526
8208
pH=11.30, pKa=11.32
12,000
11,000
10,000
E
228 mµ
9,000
8,000
0
2
4
6
8
10
12
pH
Figure 29.
E versus pH of Ben.zamidine
Hydrochloride by Method
1.
14
100
Table XXXVII. Dissociation Constants of Benzamidine
Hydrochloride by Method II.
7\
(mµ)
E at
E
pH 1.00
200
205
210
215
220
225
228
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
21965
10405
6590
7399
9075
10549
10983
10925
9538
7023
4191
2023
1012
pH 13
pKa
at
pH 11.00
E
17486
10694
7312
7775
9075
10260
10231
9971
8526
6358
4191
2572
1561
1243
1012
954
665
434
5780
6156
6561
6936
7803
8786
8815
8613
7312
5780
4335
3353
2428
1763
1243
954
29
173
58
87
58
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
867
751
867
636
347
173
520
173
11.27
11.15
11.09
10094
a
11.15
11.20
11.14
10.95
16,000
101
opH
14,000
1000
.pH 1100
ApH 13000
12,000
10,000
8,000
6,000
4,000
2,000
0
I
i
,
220
200
t
i
240
260
( mit,
Figure
30.
280
i
i
300
)
versus
ofBenzamidine Hydrochloride
by Method II.
E
ïA
i
320
102
Table XXXVIII.Dissociation Constants of Hydrazobenzene
by Method I.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
pH
0.00
0.45
0.95
1.40
1.86
2.35
2.70
3.20
3.74
4.24
4.79
5.31
5.65
5.96
6.55
6.99
7.30
7.75
8.20
8.66
9.05
9.63
10.17
10.50
11.00
11.50
12.00
12.50
13.00
13.50
14.00
E at
213 mµ
E at
239 mµ
E at
245 mµ
10994
10148
9725
9725
9302
9091
8964
8879
9006
9091
9006
8753
8837
9091
8668
8964
9091
8964
8795
8457
8372
8457
8034
8372
8795
8879
8245
16279
31459
59197
13742
13615
13784
13658
13827
14715
14926
14968
15180
15222
15053
14799
14757
15518
15180
14799
14715
14461
13784
13531
13277
13277
12727
12474
12685
12051
12262
12474
13235
12896
13953
14588
14757
14672
14419
13700
13277
13192
13319
13446
13531
13319
13066
13023
13742
13573
13108
13023
12854
12220
11628
11501
11416
10825
10613
10698
10106
10233
10571
11205
9937
10359
-
E at
290 mµ
E at
318 mµ
1564
1522
1649
1818
2622
3594
3636
3552
3679
3679
3636
3721
3679
3594
3510
3805
3848
3890
4017
4059
4059
4144
4313
4397
4355
4482
4482
4482
4397
4482
4609
2452
2410
2622
2748
2833
2706
2664
2791
2537
2537
2579
2875
2875
2283
2156
3002
3087
3214
3848
3890
4059
4186
4693
4989
4863
5666
5243
5201
4905
6131
5877
103
Table XXXVIII.
(Continued)
2\=213 mµ,
x= 8900, E= 9800, y=11000,
pH=0.90, pK = 0.93
?\=239 mµ,
x=13600, E=14500, y=15300,
pH=2.30, pKa= 2.30
x=12100, E=13500, y=15150,
pH=8.80, pKa= 8.87
x=12100, E=13000, y=14000,
pH=13.10, pKa=13.15
x=13200, E=13900, y=14700,
pH=1.65, pKa= 1.70
x=10400, E=12000, y=13500,
pH=8.40, pKa= 8.37
2\=245 mµ,
?\=290 mµ, x=
2\=318 mµ,
a
a
1500, E= 2500, y= 3650,
pH=1.80, pKa= 1.86
x= 3650, E= 4100, y= 4500,
pH=8.80, pKa= 8.75
x= 2400, E= 3800, y= 5400,
pH=8.75, pKa= 8.80
16,000
239 m
o
o
12,000
245 mµ
o
o
o
o
mp,
E
8,000
318 mµ
4,000
290
0
I
0
I
2
I
I
4
I
I
1
I
6
I
I
10
8
pH
Figure 31.
E versus
pH of Hydrazobenzene by Method
I.
I
I
12
mp,
i
14
105
Table XXXIX.
a ( mkt
210
215
220
225
230
235
239
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
)
Dissociation Constants of Hydrazobenzene
by Method II.
E at
E at
pH 7.00
pKa
pH 1.00
pH 1.84
E
10359
2748
2283
4863
7611
9979
10825
10825
10444
9006
6089
3044
1268
211
1438
1480
1776
2199
2579
3087
3510
3975
4186
4186
14799
7780
6850
8203
10148
11628
12220
12178
11628
10233
8245
5708
4228
3383
2918
2791
2960
3298
3510
3805
4101
4313
4482
4440
10994
8161
8795
10359
11966
13066
13277
13192
11416
8118
4693
2664
2072
2283
2748
3383
3975
4186
4144
4144
4186
4228
4271
4228
-
1.65
1.70
1.78
1.72
1.72
-
1.49
1.77
1.75
1.68
1.51
-
E
29810
30190
23467
16913
14165
13362
13023
12770
10825
7696
4355
2875
1860
2114
2622
3383
3975
4440
4651
4136
4989
5159
5201
5201
pH 13
pKa
-
-
1.86
1.60
1.48
-
1.49
1.77
1.86
1.93
1.95
-
106
`
14,000
v pH
1.00
pH
1.84
pH
7.00
A pH
13.00
12,000
10,000
8,000
E
6,000
4,000
2,000
o
210
Figure 32.
230
E
versus
250
2
270
?Am4)
290
310
330
of Hydrazobenzene by Method II.
107
Table XL.
No.
Dissociation Constants of 4- Methylpyrimidine by Method I.
pH
4
0.38
1.17
1.49
2.43
3.36
5
4.40
6
5.16
5.97
7.09
7.63
8.40
9.23
10.33
11.20
12.00
13.00
14.00
0
1
2
3
7
8
9
10
11
12
13
14
15
16
E at
242 mµ
4869
5115
5069
4147
3487
3410
3364
3379
3349
3333
3425
3379
3395
3289
3226
3379
3395
E at
244 mµ
.
5192
5253
5161
4209
3518
3425
3379
3364
3333
3303
3425
3395
3379
3287
3257
3303
3349
7\=242 mµ,
x=3350,
E=4300,
y=5125,
pH=2.30,
pKa=2.24
a=244 mµ,
x=3350,
E=4350,
y=5250,
pH=2.35,
pKa=2.30
5,500
5,000
4,500
E
4,000
3,500
3,000
I
I
2
0
4
8
6
10
pH
Figure
33.
E versus pH of 4- Methylpyrimidine by
Method
1.
12
14
109
Dissociation Constants of 4- Methylpyrimidine by Method II.
Table XLI.
?\(m11)
E at
pH 1.05
200
203
205
207.5
210
215
220
225
230
235
240
242
244
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
1774
2074
2558
2849
2535
1551
1306
1659
2496
3725
4892
5108
5207
5177
4155
2465
1068
530
307
192
107
69
38
23
8
0
0
0
0
E at
pH 2.21
E
pH 6.95
pKa
3879
3379
3034
2458
1882
937
768
1175
1997
3072
3994
4140
4148
4094
3072
1528
691
422
338
269
184
3994
3149
2727
2151
1613
730
568
891
1559
2458
3226
3333
3333
3303
2381
1006
530
422
369
292
215
123
77
31
138
77
31
0
0
0
0
0
0
0
0
0
0
-
2.10
1.82
-
1.98
2.05
2.20
2.14
2.13
2.10
2.07
2.02
1.96
1.89
-
2.21
-
1.81
-
pH 13
pKa
E
0
0
0
0
0
0
230
691
1459
2366
3157
3318
3341
3303
2660
1091
545
422
361
300
215
138
77
31
0
0
0
0
0
_
--
-
-
2,28
2.21
2,21
2.24
2026
2.18
2.14
2.09
2.07
1.79
1.88
1.80
-
2.08
1.81
1.81
-
-
-
110
6,000
V pH
1.05
pH
2.21
pH
6.95
o
5,000
pH 13.00
4,000
3,000
E
2,000 ¡
i
1,000
0
AAA A'
200
220
0
I
1
1
1
1
240
.
1
,
1
260
i
280
A(m)
Figure 34.
E versus T of 4- Methylpyrimidine
by Method II.
300
320
111
Table XLII,
No.
pH
1
0.00
2
0.45
1.00
1.42
1.60
1.80
2.00
2.21
2.45
2.55
2.69
2.80
3.12
3.34
3.60
3.88
4.26
4.56
4.96
3
4
5
6
7
8
9
9A
9B
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
5..50
6.01
6.47
7.02
7.48
7.82
8.32
8.71
9.29
9.85
10.42
10.95
11.50
12.00
12.50
13.00
13.50
14.00
Dissociation Constants of m- Phenylenediamine Dihydrochloride by Method I.
E at
210 mµ
2536
1902
2061
1966
1966
2473
2283
2790
2885
2885
3171
3361
3868
4280
5073
6658
11097
11034
21972
29423
33925
34750
35794
35724
35933
36421
36072
36281
36212
35794
36560
36630
36490
35376
24861
21031
15320
E at
235 mµ
E at
240 mµ
222
317
254
317
444
951
1300
2029
2632
3932
5231
5517
5897
6563
7292
7292
7451
7578
7578
7356
6975
6848
6722
6627
6894
6755
6895
6964
6825
476
1110
1554
2410
3171
4851
6309
6817
7387
7958
8751
9036
9195
9290
9131
9036
8339
7895
7610
7578
7730
7660
7660
7730
7760
7730
7660
7591
7730
7730
7730
7660
7730
7660
7660
6894
6775
6685
6894
6964
6894
6964
6894
6755
6894
E at
290
m
0
0
0
127
159
317
412
698
951
1046
1110
1205
1363
1395
1427
1522
1585
1585
1776
1871
1934
1966
2019
2019
2019
2019
1950
2019
1950
1950
1950
2019
2089
2019
2089
1950
1950
112
Table XLII.
)\=210 mµ,
(Continued)
x= 2000, E=19000, y=36000, pH= 4.80, pKa=. 4.80
a
x=14600, E=26000, y=36600, pH=13.00, pKa=12o97
2\=235 mµ,
x=
225, E= 5000, y= 9275, pH= 2.25, pKa= 2.20
x= 7575, E= 8400, y= 9275, pH= 4.90, pKa= 4.92
2\=240 mµ,
x=
200,
E= 4000, y= 7700, pH= 2.25, pKa= 2.24
a
x= 6600, E= 7200, y= 7750, pH= 4.90, pKa= 4.86
T=290 mµ, x=
0,
E=
700, y= 1400, pH= 2.20, pKa= 2020
x= 1400, E= 1700, y= 2000, pH= 4.85, pKa= 4.85
a
32,000
24,000
E
16,000
8,000
o
0
2
4
8
6
10
14
12
pH
Figure 350
E versus pH of
m- Phenylenediamine Dihydrochloride by Method
I.
235 mµ
8,000
.
240
mp.,
6,000
E
4,000
290 mµ
2,000
i
2
1
1
4
6
10
8
t
14
12
pH
Figure 36.
E
versus pH of m- Phenylenediamine Dihydrochloride
by Method
10
115
Table XLIII.
(mµ)
200
205
210
215
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
Dissociation Constants of m- Phenylenediamine Dihydrochloride by Method II.
E at
E at
pH 7.05
pKa
pH 1.05
pH 2.30
E
10028
7660
2298
18106
8357
2786
1950
2437
3621
4526
4666
3900
2437
1184
418
279
279
418
19638
30641
36072
28203
17409
10794
8565
7660
6894
5153
3343
1532
696
557
557
348
487
766
836
766
627
418
209
70
0
0
0
0
0
0
0
0
0
0
0
0
627
696
696
627
279
70
70
0
0
0
766
1114
1602
1950
2019
1671
905
348
139
70
0
0
-
m
2.33
2.19
2.28
2.48
-
2.30
2.22
2.19
2041
2.56
2.64
-
pH 13
pKa
E
23189
23538
30710
23189
15669
10306
8357
7799
6964
5223
3273
1602
836
627
836
1114
1602
2019
2019
1671
905
418
70
70
0
--
-
-
-
2.31
2,21
2.29
2049
-
2.40
2.30
2.19
2.41
2.58
2.64
-
116
28,000
vpH
1.05
pH
2.30
PH
7.05
,
pH 13.00
24,000
20,000
16,000
12,000
8,000
4,000
0
200
220
240
260
280
2\(m4)
Figure 37.
E versus
of m-Phenylenediamine
Dihydrrochloride by Method II.
2\
300
320
117
Table XLIV.
Dissociation Constants of o- Phenylenediamine by Method I.
No.
PH
E at
230 mµ
E at
290 mµ
1
0.00
2
0.41
1.03
1.34
1.84
2.60
3.55
4.55
5.00
6.05
6.95
8.13
9.14
10.30
11.00
12.00
13.00
14.00
1480
3855
7151
8659
9078
9078
8547
7123
6871
6620
6536
6704
6564
6620
6592
6788
6955
8659
140
587
1061
1257
1397
1368
1620
2514
2793
2905
2877
2961
2933
2905
2877
2961
2933
2933
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
T=230 mµ, x=1000, E=5500, y=9100,
pH= 0.75, pKa= 0.65
x=6500, E=7500, y=9100,
pH= 4.25, pKa= 4.45
x=6500, E=7400, y=8650,
pH=13.50, pKa=13.63
x= 150, E= 850, y=1400,
pH= 0.75, pKa= 0.65
x=1350, E=2100, y=2950,
pH= 4.20, pKa= 4.26
2\=290 m4,
a
8,000
230 mµ
O
6,000
E
4,000
290 mµ
2,000
1
I
2
I
1
4
I
I
1
1
6
1
8
1
10
PH
Figure 38.
E versus pH of o- Phenylened.i,amine
by Method
I.
1
I
12
I
14
119
Dissociation Constants of o- Phenylenediamine by Method II.
Table XLV.
7\
(
m
)
E at
pH 1.22
200
205
210
215
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
16408
7095
3548
3525
4767
6275
6940
5987
3836
1973
887
576
687
865
1153
1397
1486
1419
1109
710
355
155
67
22
0
E at
pH 4.87
26763
28204
23392
12195
7539
7095
7251
6674
5255
3326
1840
1131
998
1109
1330
1729
2106
2395
2350
1973
1330
732
333
111
44
E
pH 7010
pKa
27716
37428
31486
16186
8204
6563
6541
6319
5432
3814
2328
1486
1197
1175
1353
1774
2306
2772
2882
2550
1774
1064
466
177
44
-
4.51
4.48
4.53
-
4.43
4.54
4.68
4.68
-
4.38
4.46
4.50
4.53
4.53
4.63
-
pH 13
pKa
E
8891
10754
13348
13348
7982
6208
6098
5920
5100
3547
2106
1330
1020
998
1197
1574
2195
2661
2772
2439
1663
976
443
155
0
-
4.32
4.43
-
m
4.31
4.40
4.44
4.40
4.50
-
120
40,000
32,000
O pH
1.22
pH
4.87
pH
7.10
.
pH 13.00
24,000
E
16,000
8,000
200
220
260
240
7\
Figure 39.
280
(mkt)
E versus A of o- Phenylenediamine
by Method II.
300
320
121
Table XLVI.
Dissociation Constants of p- Phenylenediamine by Method I.
pH
No.
E at
240
1
0.50
1.34
1.86
2,29
3.05
3.65
4.39
4.89
5.27
6.45
6.96
8.03
9.08
10.13
11.12
12.00
13,00
14.00
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
mµ,
230
424
1131
2385
5724
7474
7650
7915
7650
8481
8834
8993
8816
8905
8958
8870
9011
9028
E at
305 mil
18
18
18
106
247
406
601
954
495
1431
1502
1572
1502
1555
1572
1555
1572
1555
A=240 mµ, x= 250, E=4000, y=7500,
x=8000, E=8500, y=8900,
pH=2.65, pK =2.62
A=305
E= 200, y= 400,
pH=2.60, pKa=2.60
x=1000, E=1300, y=1500,
pH=5.80, pKa=5.62
mu.,,
x=
0,
a
pH=6.10, pKa=6.10
a
a
240 mµ
8,000
6,000
E
4,000
2,000
A
0
A
i
4
0
i
i
i
A
A
E versus
-
1
6
8
10
pH
Figure 40.
-_
305 mµ
pH of p- Phenylenediamine by Method I.
12
14
123
Table XLVII.
A (mµ)
Dissociation Constants of p- Phenylenediamine by Method II.
E at
pH 1.14
210
215
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
2059
235
147
147
191
221
221
206
191
176
132
45
15
15
15
15
15
15
15
15
15
15
15
E at
pH 6.28
4118
3132
3971
5735
7500
8500
8088
6324
4412
2500
1324
765
588
735
794
956
1029
1029
971
956
838
662
441
E
pH 6.95
pKa
4632
3118
3794
5221
6985
8132
8397
7500
5662
3559
1941
1029
632
485
559
735
955
1147
1265
1324
1206
956
603
5.68
-
-
5.87
5.64
5.75
5.94
5.99
5.85
-
5.77
5.87
5.93
5.94
5.86
_21112_
E
4383
4691
4765
5662
6985
8235
8750
8088
6221
3897
2132
1029
632
397
471.
735
955
1235
1471
1529
1397
1074
706
pKa
-
6.01
®
-
5.91
6.06
6.11
5.85
-
6.00
6.06
6.11
6.08
6.07
10,000
8,000
v pH
1.14
pH
pH
6.28
o
6.95
pH 13.00
6,000
1
E
4,000
2,000
0
'
210
Mimayo...
230
250
.
270
-
-
290
310
A (mP,)
Figure 41.
E versus
7\
of p- Pheneplenediamine by Method II.
330
125
Table XLVIII. Dissociation Constants of Phenylhydrazine
by Method I.
No.
pH
1
0.00
2
0.51
1.02
1.34
1.85
2.44
2.89
3.52
4.08
4.58
4.81
5.15
5.50
5.86
6.25
6.65
7.02
7.25
7.46
8.15
8.80
9.40
9.78
10.26
10.91
11.50
12.00
12.50
13.00
13.50
14.00
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
E at
230 mµ
4967
4901
4283
4702
4746
4967
4879
4812
4967
4296
5077
4967
5232
6711
5938
5585
5585
4614
5938
6159
6071
6512
6313
6004
5166
6291
5320
6291
6071
6026
5828
E at
274
mil
1126
1060
993
1060
1038
1214
1192
1170
1214
1589
1214
1413
1347
1788
1788
1700
2141
1766
1567
1435
1435
1391
1435
1788
2605
2208
3135
2318
2384
1965
1766
T=230 mµ, x=4800, E=5450, y=6100,
pH= 6.20, pKa= 6.20
x=1100, E=1450, y=1800,
x=1400, E=1600, y=1800,
x=1400, E=2000, y=2600,
pH= 5.30, pKa= 5.30
pH= 7.50, pKa= 7.50
pH=10.50, pKa=10.50
x=1750, E=2200, y=2600,
pH=13.10, pKa=13.10
2\=274 mil,
8,000
230
mil
6,000
s
E
4,000
2,000
.
274
mp,
.
0
I
0
2
I
I
4
I
I
I
8
6
I
10
pH
Figure 42.
E versus
pH of Phenylhydrazine by Method
1.
I
I
12
14
127
Table XLIX.
Mmµ)
Dissociation Constants of Phenylhydrazine
by Method II.
E at
pH 1.02
200
205
210
215
220
225
230
235
240
245
250
255
260
265
270
274
275
280
285
290
295
300
305
310
315
320
9492
5752
4857
5188
5784
5607
4238
2428
1104
662
574
662
817
927
1038
1015
971
883
552
331
221
221
221
221
221
199
E
at
pH 7.02
pKa
pH 5.86
E
20971
9934
5298
4746
5188
6291
6711
6181
4857
3311
2141
1567
1479
1545
1700
1766
1766
1656
1413
1038
751
552
353
243
199
19757
10375
5740
4967
5077
5298
5585
5298
4371
3201
2230
1810
1788
1898
2097
2141
2141
1987
1611
1214
883
640
530
331
221
199
132
-
5.29
5.48
5.62
5.58
5.56
5.53
5.49
5.21
5.26
5.26
5.29
-
E
3532
3797
4018
4415
5077
5519
6049
6004
4989
3753
2980
2649
2517
2450
2428
2384
2362
2230
2053
1678
1280
905
684
552
486
397
pH 13
pKa
5.58
-
-
5.76
5.74
5.73
5.73
5.81
5.86
-
V pH
1.02
pH
5.86
pH
7.02
8,000
o
pH 13.00
6,000
E
i
\
4,000
%
i
.
76.;--,--qhr
Ak.--
2,000
-111r---,..._&
0
1
200
I
1
I
I
I
i
220
i
240
i
I
i
I
i
I
260
E versus
-)\
I
280
2\
Figure 43.
i
i
1
1
1
300
(mµ)
of Phenylhydrazine by Method II.
320
129
Table L.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
-2\=216
Dissociation Constants of Phthalic Acid
by Method I.
pH
1.06
1.55
1.87
2.14
2.62
3.42
3.65
4.27
4.67
4.80
5.23
5.56
6.20
6.38
7.00
7.38
8.23
9.30
10.54
11.10
12.00
13.00
14.00
E at
216 mµ
E at
229 mil
6667
6709
6878
6962
7806
9283
9409
9747
9789
9705
9283
9747
9536
9536
9578
9620
9494
9283
9241
8439
8903
7 004
6793
7975
7932
7848
7764
7637
7384
7300
7257
7131
7 004
6624
6498
6160
6160
6160
6160
6203
6034
5992
5823
5992
5949
6203
mµ, x=6650, E=8250, y=9800,
x=9500, E=9650, y=9750,
x=6800, E=8000, y=9300,
T,=229 mµ, x=7150, E=7500, y=8000,
x=6100, E=6600, y=7250,
7\=275 mµ, x=1300, E=1375,
y=1450,
x= 800, E=1050, y=1450,
E at
275
mp,
1392
1392
1350
1308
1308
1435
1392
1392
1266
1224
1055
970
844
844
886
844
844
759
675
675
759
759
886
pH= 2.85, pKa= 2<,84
pH= 5.30, pKa= 5.22
pH=12.20, pKa=12.23
pH= 2.85, pKa= 3.00
pH= 5.30, pKa= 5..39
pH= 3.00, pKa= 3.00
pH= 5.20, pKa= 5.40
10,000
8,000
6,000
229 mµ
E
4,000
2,000
275
0
i
0
I
I
2
I
4
I
1
I
6
I
I
pH
Figure
44.
E versus pH of
Phthalic Acid by Method
I
10
8
/<
I
I
12
mil,
I
14'
131
Table
a ( mP,
)
Dissociation Constants of Phthalic Acid
by Method II.
LI.
E at
pH 1.17
200
205
210
215
216
220
225
229
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
E at
pH 5.48
E
pH 6.99
pKa
16557
16076
8861
6582
6633
7165
7823
7949
7924
7139
5620
3418
2101
1342
1114
1114
1241
1342
1266
987
430
31646
22532
14810
9873
9367
7671
6835
6430
6380
5671
4582
3241
2101
1342
937
835
886
27848
21519
13924
9570
8987
7468
6456
5924
5797
4835
3722
2785
1772
1215
937
937
911
709
709
608
329
101
101
25
203
51
0
0
0
0
0
0
0
0
456
785
810
25
0
0
0
0
0
-
-
5.06
5.00
5.06
5.24
5.40
_
-
5.23
5.41
5.62
pH 13
pKa
E
8431
8734
9114
8937
8608
7367
6456
5949
5823
4810
3823
2684
1823
1266
962
810
835
5oC6
4.99
5.04
5.25
5.34
759
633
354
5.12
5.37
5.59
-
76
-
0
0
0
0
0
0
-
16,000
132
14,000
V pH
1.17
pH
5.48
pH
6.99
o
pH 13.00
12,000
10,000
E
8,000
6,000
4,000
2,000
0
200
I
220
260
240
T
Figure 45.
(
mP,
280
- -
300
-
320
)
E versus 7 of Phthalic Acid by Method
II.
133
Table LII.
Dissociation Constants of Pyrimidine
by Method I.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
2\=242 mµ,
pH
0.00
0.44
1.10
1.47
1.80
2.15
2.40
2.92
3.70
4.56
5.62
6.30
6.99
7.60
8.20
8.93
9.73
10.39
11.10
12.00
12.50
13.00
13.50
14.00
x=2020, E=2520, y=3060,
E at
242 mµ
3060
2982
2734
2448
2318
2188
2135
2057
2031
2057
2031
2057
2018
2070
2044
2031
2031
2044
2031
2031
2083
2096
2031
2096
pH=1.40,
pK =1.43
a
3,200
2,800
E
2,400
242 mµ
2,000
1,600
i
i
0
2
i
i
4
i
i
I
6
i
I
pH
Figure 46.
E
versus pH of Pyrimidine by Method
i
10
8
I.
i
i
12
i
14
135
Table LIII.
T ( mp, )
Dissociation Constants of Pyrimidine
by Method II.
E at
pH 1.07
200
205
210
215
220
225
230
235
240
242
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
1888
1302
781
673
777
1016
1576
2270
2617
2700
2235
1411
516
313
260
221
191
143
109
E at
pH 1.69
1910
1172
647
464
573
820
1311
1910
2192
2305
1866
1172
412
E
pH 7.01
pKa
a
1910
1172
734
478
530
694
1128
1645
1875
1997
1584
1063
22
278
243
239
230
191
161
109
61
39
352
265
260
265
256
221
178
126
65
43
9
13
13
0
0
0
0
0
0
0
0
0
78
43
-
1.50
1.53
1.56
1.57
1.58
1.38
1.35
1.45
1.26
-
1.88
1.61
1.49
1.21
1.43
-
pH 13
pKa
E
a
0
0
0
174
326
634
1085
1628
1866
1984
1584
1050
347
256
260
260
252
226
178
122
74
39
13
0
0
0
-
1.77
1.67
1..62
1.58
1.58
1.60
1.38
1.40
1.49
1.49
-
1.80
1.54
1.55
1.21
1.31
1.55
-
136
3,000
opH
pH
1.07
1.69
opH
7.01
pH 13.00
2,500
2,000
1,500
I
/
1,000
/
/
/
/
500
/
,
0
..'
/
200
i
li I,
200
I
.
.
i
240
T
Figure 47.
E versus Ä of
1
260
( mµ )
.
1
.
1
280
^
,
300
Pyrimidine by Method II.
^
s
320
137
Table LIV.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
pH
0.00
0.46
1.13
1.38
1.69
2.00
2.31
2.65
3.10
3.55
4.00
4.32
4.74
5.06
5.51
6.01
6.53
7.00
7.50
8.05
8.55
9.15
9.51
10.06
10.46
10.96
11.50
12.00
12.50
13.00
13.50
14.00
Dissociation Constants of p- Aminobenzoic
Acid by Method I.
E at
E at
E at
E at
215 mµ 225 mµ 235 mµ 245 mµ
6897
7126
7126
7356
7126
7356
7540
7793
8046
8138
8276
8299
8437
8529
8621
8736
8736
8851
8506
8736
8782
8621
8391
8713
8736
8644
8506
7839
7586
5540
4092
1954
11379
11471
11241
11057
10552
10023
9080
8368
7333
6874
6460
5793
5149
4483
3908
3609
3402
3402
3241
3333
3425
3333
3241
3425
3425
3425
3287
3264
3218
2989
2943
2299
6897
6874
6667
6207
5977
5471
4437
3678
2759
2414
2414
2414
2874
2989
3149
3333
3218
3310
3356
3287
3218
3333
3333
3287
3218
3287
3218
3195
3195
3218
3195
3011
1379
1379
1402
1402
1494
1678
1839
2069
2322
2575
3034
3563
4483
5287
6046
6667
6552
6782
6690
6667
6529
6667
6782
6690
6483
6667
6667
6598
6575
6667
6644
6437
E at
255 mµ
690
736
943
1080
1471
2161
2989
3793
4828
5402
6092
6966
8276
9425
10621
11310
11379
11517
11609
11540
11494
11494
11632
11540
11379
11494
11563
11379
11494
11494
11494
11379
E at
265 mil
805
874
1241
1517
2322
3540
5057
6713
8529
9425
10115
10805
11747
12483
13287
13747
13770
13862
13954
13908
13908
13908
13885
13931
13885
13908
13954
13839
13908
13908
14023
13862
138
Table LV.
No.
pH
Dissociation Constants of p- Aminobenzoic
Acid by Method I.
E
275
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
0.00
0.46
1.13
1.38
1.69
2.00
2.31
2.65
3.10
3.55
4.00
4.32
4.74
5.06
5.51
6.01
6.53
7.00
7.50
8.05
8.55
9.15
9.51
10.06
10.46
10.96
11.50
12.00
12.50
13.00
13.50
14.00
at
mµ,
805
851
1379
1747
2989
4598
6644
8851
11356
12276
12644
12644
12621
12092
11954
11747
11609
11678
11724
11655
11747
11724
11609
11724
11724
11724
11724
11724
11770
11747
11908
11839
E at
285 mµ
E at
295 mµ
115
230
23
69
851
1264
2529
4483
6920
9517
12230
13149
13103
12483
11103
9862
8782
8046
7816
7701
7793
7724
7908
7816
7701
7816
7862
7839
7839
7816
7931
7839
644
1012
2115
3908
5862
8161
10414
11195
10805
9885
8069
6414
4874
3908
3655
3471
3448
3448
3540
3448
3448
3471
3494
3517
3494
3494
3563
3517
3678
3678
8046
8023
E at
305 mµ
46
69
414
621
1264
2322
3494
4874
6161
6667
6276
5517
4184
2989
1839
1195
989
989
943
943
920
943
874
920
920
920
920
920
920
920
943
943
E at
315
mil
23
23
138
230
460
828
1149
1632
2000
2207
2069
1816
1333
897
506
230
92
92
92
69
69
92
69
92
69
92
92
69
69
69
92
69
139
Table LVI.
Dissociation Constants of p- Aminobenzoic
Acid by Method I.
A
(m0
x
E
y
pH at
Inflection
Point
pKa
215
7100
1950
7900
5400
8700
8700
2.90
13.10
2.90
13.08
225
8000
3300
9700
5700
11500
8000
2.10
4.40
2.13
4.38
235
2300
2300
4600
2800
6900
3250
2.30
4.70
2.30
4.65
245
1350
4000
6700
4.55
4.56
700
5000
2800
8400
5000
11600
2.30
4.80
2.32
4.77
265
800
8500
4600
11200
8500
13900
2.20
4.50
2.21
4.50
275
800
11700
6800
12200
12700
12700
2.30
5.00
2.29
5.00
100
6600
10000
13200
13200
2.30
5.00
2.31
4.99
5600
7300
11200
11200
2.25
4.85
2.25
4.85
3300
3800
6650
6650
2.25
4.85
2.26
4.86
1100
1100
2200
2200
2.25
4.90
2.25
4.92
255
285
6700
295
0
3400
305
0
1000
315
0
100
E
I
2
4
i
I
6
8
1
10
1
12
14
pH
Figure 48.
E versus pH of p- Aminobenzoic Acid by Method I.
o
16,000
12,000
8,000
E
4,000
0
2
4
6
8
10
12
pH
Figure
49.
E
versus pH of p- Aminobenzoic Acid by Method
I.
14
142
Table LVII.
À (mp )
Dissociation Constants of p- Aminobenzoic
Acid by Method II.
at
E
pH 0.95
210
215
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
4506
6897
9770
11310
10115
6897
3218
1379
851
805
851
989
1080
1011
851
437
345
276
230
230
115
92
23
E
at
pH 3.00
6207
7862
8690
7609
5172
2989
1977
2184
3103
4460
6161
8000
9540
10690
11356
11563
11149
9908
8115
5954
3747
1977
828
E
pH 7.10
pKa
11494
8736
5747
3402
2598
3264
4667
6621
9080
11494
13333
13885
13195
11770
10023
7862
5655
3540
1977
966
368
115
23
-
2.96
-
3.06
2.72
-
2.92
2.63
-
-
pH 13
E
5402
5632
5598
2989
2414
3218
4598
6621
8966
11471
13264
13885
13149
11724
9954
7885
5701
3540
1954
920
322
115
46
pKa
-
-
3.10
2.75
-
-
-
2.92
2.63
-
-
143
14,000
opH
0.95
'pH
3.00
°pH
7.10
pH
13.00
12,000
10,000
E
8,000
6,000
4,000
2,000
0
,
1,
210
I
230
,
I
I
.
250
1
1
1
1
1
270
1
1
290
,
,
310
T(mkt)
Figure 50.
versus
of p-Aminobenzoic Acid by
Method :11.
E
2\
330
144
Table LVIII.
No.
Dissociation Constants of m- Aminophenol
by Method I.
pH
E at
231
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
0.00
0.60
1.00
1.49
2.00
2.53
3.11
3.65
4.25
4.79
5.30
5.68
6.31
6.65
7.01
7.50
8.12
8.59
9.15
9.70
10.06
10.54
11.00
11.50
12.00
12,50
13.00
13.50
14.00
547
547
x= 825, E=1400, y=2000,
mp,
832
832
875
875
875
788
963
985
1400
1707
1838
656
613
700
656
963
1860
3786
5536
6346
6521
6740
6783
6849
6849
6871
6915
7155
7462
7812
8162
8315
8162
8315
8271
8534
8972
9409
T=231 mµ, x= 500, E=3750, y=6850,
x=6850, E=7600, y=8300,
x=8275, E=8800, y=9400,
7\=281 mµ,
E at
281
mil
1860
1904
1947
1969
1969
1969
1969
2035
2013
1991
1991
1991
2035
1991
1991
2035
2013
1751
pH= 4.25, pKa= 4.23
pH= 9.85, pKa= 9.82
pH=13 35, pKa=13o41
pH=
425, pKa= 4.27
10,000
8,000
6,000
E
4,000
2,000
o
0
2
4
6
8
pH
Figure
5 -1e
E versus
pH of m- Aminopheno1 by Method I,
10
12
14
146
Dissociation Constants of m- Aminophenol
by Method II.
Table LIX.
7\
(mµ.)
E
at
pH 1.00
210
215
220
225
230
231
235
240
245
250
255
260
265
270
275
280
281
285
290
295
300
305
310
315
320
5777
6214
5689
2845
656
438
350
394
438
656
919
1751
1751
1969
1882
788
613
44
0
0
0
0
0
0
0
E
at
pH 4.34
12472
8403
6171
4814
4114
4026
3720
2845
1838
1050
919
1400
1751
1751
1882
1751
1751
1094
700
263
131
88
44
0
0
E
pH 7.05
pK a
18381
10722
7090
6652
7002
7002
6565
5252
2976
1532
1444
1400
1532
1751
1882
1969
1969
1969
1663
613
263
131
88
44
0
4.28
4.37
-
4.31
4.26
4.26
4.26
4.33
4.25
4.43
-
4.26
4.48
4.46
4.34
-
pH 13
E
29278
28615
19256
12254
8972
8753
8140
7615
6127
3807
1882
1751
1313
1532
1751
2188
2188
2670
3063
2801
1969
875
219
175
44
pK a
-
4.49
4.46
4.46
4.52
32,000
147
`A
28,000
°pH
7005
'
1
pH 13.00
i
24,000
pH
1.00
4.34
°pH
li
¡
1
20,000
E
1
1
i
1
16,000
¡
12,000
4
8,000
4,000
o
1
I
,,.-'am.
1
230
210
li
.
1
I
250
1
1
-
i
270
.
290
,_310
.
w
1
7\(mil)
Figure
52.
E
versus
7
of m- Aminophenol by Method II.
I
330
148
Table LX.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
?\=228 m41,
?\=281 mµ,
Dissociation Constants of o- Aminophenol
by Method I.
pH
0.00
0.44
0.94
1.57
2.00
2.49
3.01
3.51
4.10
4.50
5.00
5.51
5.97
6.55
7.02
7.49
8.02
8.50
9.00
9.49
9.99
10.52
11.00
11.50
12.00
12.50
13.00
13.50
14.00
E at
228 mµ
832
582
582
624
832
832
790
1165
2121
3286
5616
5824
6198
6364
6531
6531
6572
6572
6448
6160
6076
6076
6034
6076
5907
5696
5992
7511
11392
E at
281
mµ,
832
749
749
749
832
832
832
1248
1498
1747
2121
2371
2579
2621
2704
2621
2662
2704
2704
2616
2489
2489
2447
2363
2363
2363
2532
2532
2489
x= 550, E=3750, y= 6600,
pH= 4.55, pKa= 4.50
x=6075, E=6325, y= 6600,
pH= 9.20, pKa= 9.28
x=5750, E=8000, y=11400,
pH=13.60, pKa=13.78
x= 725, E=1800, y= 2700,
pH= 4.50, pKa= 4.42
E
0
Figure
0
4,000
8,000
12,000
16,000
9.
1
1
t
4
1
1
6
1
1
pH
8
t
E versus pH of Benzoic Acid by Method I.
2
I
t
10
1
1
12
I
I
14
E
Figure
4,000
8,000
12,000
14,000
53.
E
4
I
I
6
I
pH
I
8
versus pH of o- Aminophenol by Method
2
Io
10
i
I
12
I
14
150
Dissociation Constants of o- Aminophenol
by Method II.
Table LXI.
A (mµ,
)
E
at
pH 1.00
200
205
210
215
220
225
228
230
235
240
245
250
255
260
265
270
275
280
281
285
290
295
300
305
310
315
320
5443
6245
6414
5485
3840
1308
464
338
338
422
549
633
886
1350
1899
1983
1688
844
591
84
0
0
0
0
0
0
0
E at
pH 4.55
23840
17468
9072
5949
4895
3797
3671
3671
3122
2194
1392
928
928
1055
1435
1899
2025
1730
1688
1519
1266
675
295
211
169
127
42
E
pH 7.08
pKa
38144
26793
11814
6371
5738
6118
6329
6329
5696
3755
2110
1266
886
886
1139
1603
2152
2616
2700
2616
2194
1477
591
211
127
84
42
-
4.47
4.56
4.51
4.45
4.52
4.46
4045
4,51
4.49
4.48
4.61
-
4.31
4.36
-
4.55
4.51
4.43
4.41
4.63
4.55
-
E
18312
19494
20506
20211
11857
6962
6076
5992
6160
6540
6076
4557
2532
1477
1224
1350
1688
2321
2489
3122
3840
4177
3966
3080
2278
844
253
pH 13
pKa
-
4.65
4.43
4.40
4.59
-
-
4.36
-
4.38
4.41
4,60
-
-
151
28,000
o
pH
pH
1.00
4.55
pH
7.08
pH 13.00
24,000
20,000
16,000
E
12,000
8,000
'q
4,000
0
200
220
240
260
280
300
( mµ )
Figure 54.
E versus A of o- Aminophenol by
Method II.
320
152
Table LXII.
No.
Dissociation Constants of p- Aminophenol
by Method I.
pH
E at
231 mµ
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
23A
24
25
26
27
28
29
30
31
32
33
34
0.00
0.44
1.00
1.49
1.93
2.45
2.90
3.40
3.90
4.40
4.86
5.13
5.39
5.74
6.05
6.40
6.66
6.96
7.30
7.77
8.27
8.61
9.10
9.23
9.43
9.71
10.15
10.58
11.00
11.50
12.00
12.50
13.00
13.50
14.00
796
726
820
820
726
761
738
785
1066
1288
2166
2939
3864
4918
5808
6358
6546
6838
6874
7002
6850
6745
6382
6329
6011
5920
5510
4781
4781
4827
5100
5237
7013
8880
9472
E at
296 mµ
0
0
0
0
0
0
0
23
59
176
457
691
995
1323
1581
1803
1862
1897
1920
1956
1897
1814
1639
1548
1548
1275
956
683
729
774
501
501
637
683
546
153
Table LXII.
2\=231 mµ,
2\=296 mµ,
(Continued)
x= 700, E=3950, y=7000,
pH= 5.45, pKa= 5.42
x=4750, E=5895, y=7000,
pH= 9.70, pKa= 9.70
x=4750, E=7250, y=9475,
pH=13.05, pKa=13.00
x=
E=1000, y=1945,
pH= 5.40, pKa= 5.38
x= 700, E=1350, y=1950,
pH= 9.60, pKa= 9.57
0,
a
10,000
231
mµ,
8,000
6,000
E
4,000
Pow
2,000
296 mµ
.---v
,..
o
n
0
ft
ft
et
2
I
4
i
I
i
I
1
6
I
8
i
I
i
pH
Figure
55.
E versus
pH of p- Aminophenol by Method To
I
10
i
I
i
I
12
i
43"°....b
I
i
14
155
Dissociation Constants of p- Aminophenol
by Method II.
Table LXIII.
2\(m[1)
at
E
pH 1.00
210
215
220
225
230
231
235
240
245
250
255
260
265
270
275
280
285
290
295
296
300
305
310
315
320
6466
6785
6421
3734
1457
1412
1002
1047
1002
1002
1412
1594
2049
1867
1639
1594
546
364
273
273
319
410
455
455
319
E
at
pH 5.45
5738
5692
5920
5237
4508
4463
4007
3142
2095
1457
1093
1366
1184
1412
1412
1594
1366
1548
1548
1594
1594
1275
1138
1002
455
E
pH 7.06
pKa
5009
4645
5465
6648
7559
7559
7195
6011
3962
2732
1958
1639
1594
1184
1639
1639
1913
2231
2322
2322
2277
2049
1639
1366
911
5.45
5.43
5.41
5.42
5.45
5.45
5.48
5.59
-
5.28
5.21
5.24
-
5.40
5.31
5.28
-
E
16940
16667
11430
8379
8151
8197
8880
10246
10838
11384
10337
9381
6557
3643
2049
1594
1639
1685
1821
1821
2049
2322
2459
2368
2095
pH 13
pKa
-
5.53
5.54
5.66
-
-
-
5.53
5.73
5.85
-
156
16,000
vpH
1.00
pH
5.45
°pH
7.06
14,000
pH 13.00
12,000
Ant
10,000
E
I!
;
.f
8,000
;
6,000
4,000
2,000
0
-a'
,
210
I,
I, 1, l, I, I, I, I,
230
250
270
290
T
Figure 56.
E versus A
(
mp
Ili
I
310
)
of p-Aminophenol by Method II.
330
157
Table LXIV.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
pH
0.00
0.38
1.00
1.36
1.77
2.14
2.58
3.20
3.87
4.45
4.98
5.65
6.05
6.48
7.05
7.52
7.90
8.52
9.08
9.72
10.40
10.95
12.00
12.50
13.00
13.50
14.00
Dissociation Constants of Anthranilic Acid
by Method I.
E at
216 mµ
E at
220 mµ
E at
226 mµ
240 mµ
E at
6513
6513
6933
8403
10504
13025
15504
17647
18067
18655
19328
19328
19748
19328
19748
19748
19748
19748
19748
20168
19538
19538
18950
16807
12899
8613
8193
8824
8782
9034
10084
11387
13193
14916
16176
15966
15672
15210
14286
14286
13655
13950
13655
13866
13782
13866
14286
13866
13782
13487
12395
11513
9076
8529
11093
10756
10714
10840
10504
10504
10420
9874
9244
9160
8950
8403
8403
8151
8319
8067
8109
8067
8193
8403
8193
8319
7983
7689
7647
7143
7353
4202
3992
3866
3908
3866
4202
4160
4244
4328
5000
5882
6975
7227
7311
7269
7311
7311
7353
7353
7437
7395
7395
7553
7553
7553
7553
7269
E at
310 mµ
342
342
378
504
630
840
1008
1218
1303
1765
2227
2857
2983
3067
3067
3109
3067
3109
3067
3109
3151
3151
3109
3109
3109
3109
3235
158
Dissociation Constants of Anthranilic Acid
by Method I.
Table LXV.
T
x
E
y
(mµ)
pH at
Inflection
Point
pK
a
216
6500
18000
8200
12300
18900
14000
18000
19750
19750
2.05
4.65
12.85
2.04
4.63
12.85
220
8800
13800
8500
12500
15000
11300
16100
16100
13900
2.00
5.00
13.00
1.99
4.96
12.97
226
9200
8100
7100
10000
8600
7700
10700
9200
8300
3.10
5.50
12.85
3.04
5.58
12.85
240
3800
4250
4025
5800
4250
7300
2.05
4.90
2.05
4.87
310
350
1200
775
2150
1200
3100
2.10
4.90
2.10
4.90
216 mµ
A
20,000
16,000
12,000
E
8,000
4,000
i
t
0
2
1
i
4
i
i
i
i
1
8
6
1
10
pH
Figure
57.
E
versus pH of Anthranilic Acid by Method
I.
i
1
12
1
i
14
8,000
240 mµ
6,000
E
4,000
310 mµ
JIM
.
2,000
I
2
I
I
4
I
1
i
I
8
6
i
i
10
pH
Figure 58.
E versus
pH of Anthranilic Acid by Method 1.
1
1
12
1
14
161
Dissociation Constants of Anthranilic Acid
by Method II.
Table LXVI.
(mµ)
200
205
210
215
220
225
227
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
E at
E at
pKa
15966
17479
20126
18908
15294
9664
7983
6765
5882
5462
4748
3445
1681
714
21639
27312
27731
20798
13403
8361
7563
6975
7185
7311
6387
4580
2353
1050
-
126
126
588
588
714
1261
1555
2017
2395
2773
3109
3109
2941
2647
pH 4.66
22899
6849
5462
6849
9160
10840
10840
10168
7437
3782
1849
1218
966
1050
1050
1176
1092
966
714
252
168
252
336
336
336
336
pH 7.05
E
pH 1.00
210
294
714
966
1345
1471
1807
1891
1975
1933
4.71
-
4.70
4.42
4.37
4.63
-
4.83
4.61
4.69
4.61
4.55
4.52
4.31
E
13403
14244
15336
16471
12605
8445
7563
7227
7437
7563
6891
5042
2689
1471
714
840
924
1303
1681
2059
2521
2857
3151
3235
3025
2689
pH 13
pKa
-
-
4.68
-
4.76
4.53
4.52
4.81
-
4.84
4.66
4.72
4.62
4.59
4.55
4.33
162
28,000
v pH
1.00
pH
4.66
pH
7.05
°
pH 13.00
24,000
16,000
E
12,000
200
220
240
260
280
300
320
A (mu)
Figure
59.
E versus
T
of Anthranilic Acid by Method II.
163
Table LXVII.
No.
pH
Dissociation Constant of Nicotinic Acid
by Method I.
E at
212.5 mµ
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1.13
1.40
2.40
3.12
4.09
4.48
5.14
6.04
7.03
7.82
9.17
10.20
11.18
12.00
13.00
14.00
5464
5357
5571
5750
6250
6696
7321
7679
7679
7857
7839
7589
6607
6500
2946
3393
E at
220 mµ
E at
255 mµ
E at
260 mµ
E at
262 mµ
4286
3964
3839
3750
4161
4732
5250
5804
5857
6071
4339
4339
4250
4089
3929
3589
3196
2839
2768
2732
2732
2750
2768
2821
2768
2768
5179
5161
4982
4750
4464
4036
3482
2964
2911
2893
2875
2857
2911
2893
2875
2857
4464
4286
4429
4446
4268
3964
3464
6071.
6071
5536
5714
4732
5214
À=212.5 mµ, x=5500,E=6800, y=7900,
x=2400,E=5400, y=7900,
3179
3125
3179
3179
3214
3179
3196
3161
3179
E
269
at
mp,
2679
2679
2679
2768
2768
2732
2500
2321
2321
2375
2375
2375
2339
2357
2357
2357
pH= 4.60, pKa= 4.49
pH=12.30,
pKa=12.22
x=3750, E=5000, y=6100,
pH= 4.80, pKa= 4.74
x=4700, E=5400, y=6100,
pH=12.30, pKa=12.30
7\=255 mµ,
x=2725, E=3500, y=4350,
pH= 4.65, pKa= 4.71
)\=260 mµ,
x=2900, E=3800, y=5000,
pH= 4.80, pKa= 4.92
1\=262 mµ,
x=3100, E=3750, y=4450,
pH= 4.80, pKa= 4.83
2\=269 mµ,
x=2350, E=2600, y=2800,
pH= 4.90, pKa= 4.80
7\=220 mµ,
8,000
6,000
E
4,000
2,000
269
0
1
i
0
2
i
I
4
I
I
1
I
6
I
8
I
10
pH
Figure 60.
E
versus pH of Nicotinic Acid by Method
I.
mµ,
I
I
12
I
I
14
165
Table LXVIII. Dissociation Constants of Nicotinic Acid
by Method II.
T (mp.)
E at
pH 1.28
200
205
210
212.5
215
220
225
230
235
240
245
250
255
260
262
265
266.5
269
270
275
280
285
290
295
300
305
310
315
320
2571
3482
5196
5348
5179
4107
2411
902
759
1143
1875
2947
4197
5089
4732
3982
3964
2321
1964
357
71
18
9
0
0
0
0
0
0
E at
pH 4.85
7054
6964
7000
6786
6384
4821
3125
2045
1598
1625
1982
2616
3393
3839
3929
3402
3179
2679
2411
804
268
116
45
E
pH 7.06
pKa
7545
7411
7723
7679
7321
5714
3661
2188
1598
1607
1795
2223
2768
2947
3179
2536
2304
2321
2143
554
143
45
18
27
18
0
0
0
0
0
0
0
0
0
0
-
4.65
4.74
4.95
4.73
-
4.93
4.73
4.70
4.82
5.02
4.90
-
pH 13
pKa
E
3571
3705
3839
4018
4643
5000
3393
2054
1580
1563
1786
2188
2652
2902
3143
2455
2277
2277
2054
536
134
36
18
9
0
0
0
0
0
-
-
4.96
4.79
4.73
4.84
5.06
4.91
--
--
-
166
7,000
o pH
pH
pH
pH
1.28
4.85
7.06
13.00
6,000
5,000
E
4,000
3,000
2,000
1.000
0
I
200
1
I
1
I
1
220
I
I
240
i
I
260
?\
Figure 61.
E versus
2\
1
I
280
300
320
(mµ-)
of Nicotinic Acid by Method II.
167
Table LXIX.
Dissociation Constants
Acid by Method I.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
T,=247.5
mp,,
pH
0.00
0.40
0.81
1.23
1.55
2.00
2.13
2.25
2,44
2.51
2.75
2.95
3.10
3.25
3.50
3.70
3.97
4.30
4.58
4.84
5.22
5.75
6.35
6.97
7.75
8.55
9.66
11.00
12.00
12.50
13.00
13.50
14.00
x=500, E=8000, y=15000,
of Sulphanilic
E at
247.5 mµ
300
420
601
691
871
1471
1922
2162
3063
3363
4865
6036
7297
8529
10631
11802
13063
14174
14354
14745
14985
15015
15045
15045
15015
15045
15105
15045
15105
15225
15105
15255
15495
pH=3.20, pKa=3.17
a
247.5 mµ
16,000
12,000
E
8,000
4,000
0
2
4
6
8
10
pH
Figure 62.
E versus pH of Sulphanilic Acid by Method lo
12
14
169
Dissociation Constants of Sulphanilic Acid
by Method II.
Table LXX.
E at
2\(m0
pH 1.02
210
215
220
225
230
235
240
245
247
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
9069
9069
5495
1051
420
5
511
631
661
661
661
691
661
450
420
180
180
210
180
150
180
180
180
150
150
E at
pH 3.15
9910
6186
4084
2342
3153
4775
6577
7838
8048
7928
6727
4865
3003
1892
1351
1171
1051
871
601
420
330
300
210
150
pH 7.01
E
pK
9910
3363
2432
3604
5586
8709
12042
14685
15135
14955
12613
8979
5405
3303
2342
1952
1712
1441
1141
721
480
330
210
180
-
3.14
3.22
3.14
3.10
3.11
3,11
3.13
3.13
3.14
3.14
3014
3.12
3.13
3.08
3.05
3.05
3.06
3.23
3.25
3.15
-
pH 13
pK
E
0
0
0
3003
5465
8709
12102
14655
15135
14895
12582
8859
5435
3333
2372
1982
1772
1502
1141
721
511
300
240
180
®
-
3.08
3,11.
3.12
3,13
3.13
3.13
3.14
3013
3.13
3.13
3.09
3.06
3.08
3.11
3.23
3.25
3.23
-
16,000
170
14,000
vpH
1.02
*pH
3.15
°pH
7.01
pH
13.00
12,000
10,000
E
8,000
6,000
4,000
2,000
/
0
1i ii i.
210
230
i
1
250
I.
290
270
T
Figure 63,
E
versus
'7\
(
mP.
310
330
)
of Sulphanilic Acid by Method II.
171
Table LXXI.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
A,=210 mµ,
?\=215 mp,,
Dissociation Constant of 1- Histidine
by Method I.
pH
0.10
0.48
1.11
1.58
2.17
2.77
3.40
4.00
4.48
4.90
5.29
5.79
6.25
6.64
7.00
7.40
7.90
8.30
8.95
9.60
10.16
10.79
11.50
12.00
12.50
13.00
13.50
14.00
E at
210 mµ
E at
215 mµ
5855
5913
5942
6174
6087
5913
6000
6058
6058
6029
5913
6029
5884
5797
5913
5913
5913
5855
5797
6232
6174
6667
6261
6116
5594
4638
3159
3043
5362
5188
5130
5304
5478
5246
5362
5449
5362
5304
5217
5217
4928
4841
4957
4870
4957
4928
4928
5449
5536
5623
5478
5217
5159
4812
3507
3420
x=5800, E=6200, y=6600,
pH= 9.85, pKa= 9.85
x=3000, E=4750, y=6600,
pH=13.00, pKa=13.02
x=4900, E=5150, y=5400,
pH= 5.60, pKa= 5.60
x=4900, E=5300, y=5600,
pH= 9.40, pKa= 9.33
x=3400, E=4550, y=5600,
pH=13.20, pKa=13.16
7,000
6,000
5,000
E
4,000
3,000
1
0
2
4
1
1
I
1
1
10
6
1
I
12
1
14
pH 8
Figure 64.
E versus pH of
1- Histidine by
Method
i.
o
173
Table LXXII.
a(mµ)
Dissociation Constants of 1-Histidine
by Method II.
E at
pH 1.00
200
205
210
215
218
220
225
230
235
240
245
250
255
260
265
270
275
280
285
290
295
300
305
310
315
320
3623
5145
5797
5014
3957
3217
1362
290
72
72
43
14
E at
5638
5942
5899
5160
4304
3696
2029
725
217
116
101
72
0
0
0
43
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
E
at pH 13
pKa
a
pH 9.48
0
0
3638
3768
3710
3986
4087
3783
2377
1000
362
217
174
130
87
72
29
14
14
0
0
0
0
0
0
0
0
0
-
9.19
9.28
9.48
9.84
9.58
9.48
9.49
174
7,000
o
6,000
pH
1.00
pH
9.48
pH 13.00
5,000
4,000
3,000
2,000
1,000
0
200
220
260
240
7\
Figure 65.
E versus
7
280
(mµ,)
of 1- Histidine by Method II.
300
175
Table LXXIII.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
pH
0.00
0.45
1.05
1.65
2.28
2.77
3.20
3.70
4.14
4.40
5.05
5.55
6.02
6.51
7.05
7.41
7.90
8.31
8.96
9.61
9.92
10.52
11.00
11.50
12.00
12.50
13.00
13.50
14.00
Dissociation Constants of p Hydroxyphenoxyacetic Acid by Method I.
E at
222 mµ
E at
235 mµ
E at
285 mµ
E at
287 mµ
E at
305 mµ
6671
6439
6630
6671
6617
6821
6917
7231
7176
7190
7271
7217
7231
7231
7244
7190
7135
7108
7094
6930
6821
6276
6003
5894
5593
5703
4775
4911
4502
1228
1228
1228
1228
1228
1296
1432
1637
1637
1610
1637
1637
1569
1569
1637
1569
1637
1637
1896
2797
3684
6385
8049
8186
9168
9263
9263
9263
9304
2387
2319
2374
2374
2374
2387
2401
2456
2428
2415
2428
2428
2428
2428
2401
2415
2401
2374
2319
2183
2046
1637
1296
1228
1023
1078
955
2360
2265
2319
2319
2319
2387
2401
2483
2456
2456
2469
2469
2456
2456
2456
2456
2428
2387
2374
2251
2142
1746
1473
1378
1201
1228
1132
1160
1132
164
136
136
164
150
191
205
273
286
300
300
300
273
300
300
286
314
286
396
682
928
1801
2265
2292
2578
2606
2606
2633
2660
955
941
176
Table LXXIV.
x
Dissociation Constants of p-Hydroxyphenoxyacetic Acid by Method I.
E
y
(mµ)
pH at
Inflection
Point
pKaa
222
6600
6000
4500
6900
6550
5250
7225
7100
6000
3.10
10.30
12.75
3.13
10.30
12.75
235
1225
1600
1400
5500
1600
9300
3.10
10,30
3.15
10.29
285
950
1700
2425
10.40
10.38
287
2275
1150
2350
1850
2450
2450
2.80
10.50
2.92
10.43
305
125
300
200
1500
300
2650
3.10
10.30
3.22
10.28
8,000
6,000
4,000
2,000
287
nap,
0
0
2
4
8
6
10
12
pH
Figure 66.
E
versus pH of p- Hydroxyphenoxyacetic Acid by Method
I.
14
4,000
I-
3,000
!'
--
E
2,000
285
1,000
mil
r
0
I
o
2
1
_I_
4
t
i
t
6
I
8
t
1
1
t
10
12
I
14
pH
Figure
67,
E versus
pH of p- Hydroxyphet oxyacetic Acid by Method
I
m
179
Table LXXV
(m!,)
o
Dissociation Constants of p-- Hydroxyphenoxyacetl.c Acid by Method II.
E at
pH 1,05
200
205
210
215
220
222
225
230
235
240
245
250
255
260
265
270
275
280
285
287
290
295
300
305
310
315
320
6821
4980
5307
5771
6671
6630
5771
3138
1214
546
287
218
287
437
682
1105
1719
2115
2360
2333
2142
1569
696
150
41
27
14
E at
pH 1.052
19100
11596
6139
5184
5866
6276
6780
6862
6385
5321
3683
2046
982
573
491
600
846
1187
1569
1678
1828
1951
1910
1774
1528
1132
655
pH 13
E
764
996
1173
1610
3683
4502
6139
8322
9140
8254
5708
3179
1473
682
341
300
382
600
955
1160
1460
1978
2428
2633
2469
1910
1091
pK a
-
-
10.24
10.31
10.31
10.31
10.37
10.42
10.42
1030
10.24
10.32
10.41
1042
10.59
.
10.24
10.32
10.37
10.35
180
14,000
pH
1,05
pH 10.52
o
12,000
pH 13.00
10,000
8,000
E
6,000
4,000
2,000
0
200
i
1
I
I
I
220
.
.
I
260
A
Figure 68.
E versus
by Method
I
240
2\
(
m0
i
I
i
I
280
i
I
i
I
300
of p-Hydroxyphenoxyacetic Acid
TI
d
320
181
Table LXXVI.
No.
Dissociation Constant of d1- Tr.yptophane
by Method I.
pH
E
218
0,15
0,50
0.90
1.47
1.88
2.34
2.80
3.25
3,78
4.20
4.77
5.23
5.71
6,16
6.55
7.00
7,52
8.00
8.41
8.94
9,46
9.84
10,18
10.57
10,85
11.50
12.00
12.50
13.00
13.50
14.00
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
-N=218
rtm,,
=221 mp
7\--278 m[1,
at
mp,
33383
32885
33034
33134
33383
33632
33981
34429
34778
34629
34679
34928
34728
34679
34679
34629
34479
34380
34429
33433
33284
32636
32536
32387
31938
31839
30892
30892
29048
27554
27404
E at
221 Intl
29895
29895
29895
29895
29895
30394
30891.
31340
32387
31888
32387
32387
31888
32387
32387
32387
32387
31888
32387
32138
32387
32636
32885
32785
32885
32785
32785
31988
31141
29796
28301
=33000. E-34000, y=34900,
x-27400, E-31000, y=34400,
x-29900, E=31100, y-32400,
x=28300, E=30800, y=33000,
PKa
determinable
E at
279
Irv_
5630
5531
5580
5580
5531
5481
5431
5580
5630
5531
5531
5630
5531
5531
5531
5531
5580
5481
5580
5481
5381
5282
5282
5381
5282
5232
5232
5232
5332
5332
5182
pH= 2.70, pKa--
2
.65
pH=11.90,pKa-11,88
pH= 3.05DD,Ka= 3,08
pH=13.10,pKa-13 05
E
8,000
278
4,000
l
0
1
2
I
1
4
1
1
I
6
1
1
I
10
8
pH
Figure 69,
E versus pH of
dl-Tryptophane by Method
I.
rap,
1
1
12
1
14
183
Table LXXVII.
A(m)
Dissociation Constants of d1- Tryptophane
by Method II.
E at
pH 1.00
200
205
210
215
218
220
221
225
230
235
240
245
250
255
260
265
270
275
278
280
285
290
295
300
305
310
315
320
7474
20428
27653
33582
32885
30493
28401
16193
5481
2990
2392
2392
2691.
3338
4235
5032
5481
5481
5630
5481
4484
3039
947
199
100
50
0
0
E at
pH 9.31
20428
19831
23966
31141
33533
32985
31888
22920
7474
2740
2143
2192
2491
3039
3737
4484
5132
5282
5431
5431
4584
3737
1744
548
299
149
100
50
E
at
pH 13,00
24415
25311
26158
27703
30643
31839
31734
26657
10463
3239
2143
2093
2242
2691
3338
4086
4783
5132
5232
5282
4637
4235
2242
997
448
149
100
50
pK a
e
-
946
-.
-
9.06
949
z
9,41
9.37
9.21
9.14
9.31
9, 19
9,31
-
9,01
9.41
9.10
9.42
9.19
_.
-
32,000
pfl
1.00
pii
9..31
A pH
13,00
.
24,000
L
16,000
8,000
0
200
220
240
260
280
?,(mil)
Figure 70.
E versus
2\
of d1-Trypteaphdn by Method TT_
300
320
185
Table LXXVIII.
No.
Dissociation Constant of 1- Tyrosine
by Method I.
pH
E at
222.5
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
22A
23
23A
24
0.00
0.40
0.90
1.39
8005
8121
8121
8121
8190
8190
8306
8283
8329
8329
8329
8306
8329
8306
8237
7935
7425
7123
6845
6262
5800
5429
5452
5104
4640
3944
2784
1.95
2.54
3.15
3.92
4.73
5.68
6.04
6.49
7.01
7.55
7.95
8.50
9.05
9.32
9.61
10.07
10.37
10.90
12.00
12.50
13.00
13.50
14.00
mil
E at
240 mµ
510
534
510
510
464
394
394
348
371
371
464
464
487
510
743
1508
3016
3968
5197
7889
9258
10789
11183
11369
11323
11369
11276
E
274
at
rap,
E at
292
1369
1346
1369
1369
1392
1369
1392
1392
1415
1415
1415
1392
1415
1392
1392
1369
1346
1346
1323
1299
1230
1137
1160
1160
1114
1137
905
mp,
23
23
23
23
23
23
23
46
46
46
46
46
46
46
93
232
534
835
998
1624
1926
2251
2320
2390
2343
2390
2297
-
T=,222.5 mµ, x=5450, E=6800, y= 8300, pH= 9.60, pKa= 9.65
x=2800, E=4200, y= 5450, pH=13.40, pKa=13.:33
;=240 mµ,
x= 400, E=6000, y=11350, pH= 9.75, pKa=
T,=274
mil,,
pKa undeterminable
A=292
mp,,
x=
9..73
50, E=1300, y= 2400, pH= 9.80, pKa= 9.74
16,000
12,000
-
e
240
_
mil
a
E
8,000
4,000
222.5 mµ
292 mµ
v v
0 1 A
0
11
A
0
2
l
A
Y
4
I
I&
A
.
1
6
.
274 mµ
I
10
8
I
1
12
1
14
PH
Figure 71.
E
versuspH of 1- Tyrosine by Method
I.
rn
187
Table LXXIX.
a(mw)
Dissociation Constants of 1- Tyrosine
by Method II.
E at
pH 5.73
200
205
210
215
220
222.5
225
230
235
240
245
250
255
260
265
270
274
275
280
285
290
292
295
300
305
310
315
320
9165
5397
5295
6110
7454
7821
7230
3666
978
122
81
143
305
550
855
1120
1303
1303
1120
570
81
20
20
20
20
0
0
0
E at
E
at pH 13
pH 9.85
20367
10183
6925
6029
6680
7026
6925
5906
3971
3747
3442
2444
1405
937
916
1120
1303
1303
1303
1059
815
754
713
591
367
143
41
0
pK a
0
0
0
0
0
1018
2444
5499
8187
9776
8452
5214
2424
754
-
10.00
10.07
10.02
9.93
9.82
81
0
81
122
570
1018
1385
1466
1446
1181
672
244
102
20
9.74
9.84
9.88
9.86
9.79
188
14,000
pH
o
12,000
pH
pH
1.00
9.85
13.00
10,000
8,000
E
6,000
4,000
2,000
0
200
220
240
260
T
Figure 72.
E
versus
2\
(
280
300
m0
of 1- Tyrosine by Method II.
320
189
Table LXXX.
No.
pH
0
0.00
1
1.18
1.87
2.58
3.20
3.86
4.65
5.30
6.18
7.00
7.65
8.84
9.95
11.03
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
)=232
Dissociation Constants of 2- Amino -4,6Dichloropyrimidine by Method I.
mp,,
12.00
13.00
14.00
E at
232 mµ
10976
12846
13618
13476
13435
13394
13496
13211
13374
13394
13333
13313
13374
13333
13455
13537
15041
E
at
297.5
mil,
5163
4451
4756
4654
4634
4614
4654
4614
4634
4634
4614
4593
4634
4634
4634
4593
4472
x=10900, E=12200, y=13400, pH= 0.96, pKa= 0.92
x=13200, E=14100, y=15000, pH=13.50, pKa=13.50
A=297.5 mil,x= 4600, E= 4800, y= 5100, pH= 0.40, pKa= 0.57
16,000
232
mp,
12,000
E
8,000
*
-
.
4,000
0
I
0
2
I
I
4
I
a
+
p
297.5
I
I
I
6
8
I
I
10
I
I
12
pH
Figure 73.
E versus pH of
2- Amino- 456- Dichloropyrimidine by Method I.
mia
I
14
191
Table LXXXI.
Mmµ)
200
205
207
210
212 5
215
220
225
230
232
235
240
245
250
255
260
265
270
275
280
285
290
295
297.5
300
305
310
315
320
Dissociation Constants of 2- Amino -4,6Dichloropyrimidine by Method II.
E at
E at
pH 0.00
pH 1.18
13049
13293
13821
15854
16402
13894
13516
12703
11789
10874
8638
4472
2337
1667
1484
1524
1667
1890
2236
2744
3293
4065
4837
5142
5386
5732
5630
5000
3963
7114
8740
9797
8028
6504
5752
6504
9756
12602
12846
11890
7927
3354
1159
772
813
1016
1362
1911
2541
3333
3964
pH 7.00
E
pKa
18171
15041
12195
7419
5081
4289
5549
9350
12886
13394
12805
8943
3963
1321
854
915
1138
1545
2134
2846
3577
4268
4390
4431
4411
4634
4634
4553
3923
3069
2012
955
3963
3049
1850
833
-
0.96
-
pH
13
E
pKa
7175
7358
7439
7520
7602
7602
7825
10549
13252
13537
12642
8638
3760
1341
854
955
1179
1626
2154
2846
3598
4268
4593
4573
4512
3902
2947
1809
813
-
0.95
-
-
1.08
Lan
cey
192
20,000
o
pH
0.00
pH
1.18
pH
7.00
pH 13, 00
16,000
12,000
E
ß
CGC
4,000
0
200
I
220
if
I
240
260
7\
Fiqure 74.
(rap,
I
280
,
1,
1,
300
I,
320
)
versus
of 2-Amino-4,6-Dichloropyrimidlne
by Method II.
E
7\
193
Table LXXXII.
pH
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
-=218
0.57
0.99
2.00
2.91
3.35
3.79
4.32
5.28
6.04
7.05
8.10
9.28
9.95
10.95
12.00
13.00
14.00
mp.,
Dissociation Constants of 2-Amino -4,6Dimethylpyrimidine by Method I.
E at
218 mµ
E at
222 mµ
E at
225 mµ
10749
10628
10628
10628
10507
10266
9420
8575
8454
8213
8213
8213
8213
8575
8816
10386
17440
12101
12295
11957
12029
11860
11667
10942
10266
10121
10097
10097
10097
10024
10169
10435
11353
17029
11763
11378
11159
11353
11184
11159
11111
11087
10870
10870
10918
10894
10821
10966
11063
11643
15217
E at
E at
286 m4 295 mil
5048
5121
5092
5121
5048
5024
4831
4614
4565
4589
4589
4589
4565
4589
4589
4589
4565
6159
6159
6087
6063
.5870
5604
4831
3913
3792
3986
3841
3841
3816
3792
3744
3744
3768
x= 8200, E= 9600, y=10800, pH= 4.25, pK = 4.18
a
x= 8200, E= 9500, y=10800, pH=12.60, pKa=
?\=222 mp,,
=225
7.60
x=10000, E=11000, y=12200, pH= 4.20, pK = 4.28
a
x=10000, E=13000, y=16100, pH=13.55, pKa=1357
mµ, x=10900, E=11100, y=11200, pH= 4.60, pKa= 4.30
x=10900, E=13000, y=15200, pH=13.50, pKa=13.52
-=286 mµ, x= 4600, E= 4800, y= 5100, pH= 4.30, pKa= 4.48
D\=295
mµ, x= 3800, E= 5000, y= 6200, pH= 4.20, pKa= 4.20
a
16,000
12,000
218 mµ
E
8,000
o
286 mµ
4,000
o
o
o
295
m6
µ
1m,
0
i
1
0
2
4
6
8
t
10
12
14
pH
Figure
75.
E
versus pH of 2- Amino- 4,6- Dimethylpyrimidine by Method
I.
195
Tab1.e
( mp. )
200
205
210
215
220
222
225
230
235
240
245
250
255
260
265
270
275
280
285
286
290
295
300
305
310
315
320
LXXXIII
.
Dissociation Constants of 2-Amino-4,6Dimet.hylpyrimidine by Method II.
E at
E at
pH 7.03
pKa
pH 1.00
pH 4.00
E
10060
6763
6184
8877
11703
12017
11353
7488
2959
833
8333
5254
5254
7597
10386
10930
10990
8756
4952
531
543
664
894
930
797
990
1341
1280
1896
2754
3744
4831
4976
5676
6135
5918
5012
3502
1872
688
1812
2476
3261
4046
4698
4771
4988
4771
4094
3068
1884
906
314
6099
3973
4481
6522
9287
10085
10749
9843
6643
3007
1220
978
1208
1643
2198
2874
3575
4227
4577
4589
4420
3756
2717
1594
700
217
48
2041.
-
3.93
3.92
3.92
3.92
3089
3.82
3.93
3.93
3.90
3.86
3.85
3.83
3.83
3.86
3.84
3.79
3.78
3.96
3.95
3.91
3.87
3.88
3.88
3.86
3.85
3.85
pH
E
7971
8442
8998
9543
11123
11473
11510
9843
6401.
2838
1196
990
1220
1667
2210
2899
3611
4227
4541
4541
4384
3684
2657
1546
652
205
48
1.3
pKa
m
--
-
3,93
3.86
3082
3,83
3.88
3.85
3.86
3.88
3.86
3.84
3.78
-
3,94
3.90
3.90
3.89
3.88
3.86
3.85
196
opH
1.00
pH
4.00
'
12,000 -
pH
7003
ApH 13.00
o
10,000.
Y
8,000k
6,000
4,000
-
2,000-
0
.1,I.
200
i
220
i
i
240
I
260
i
280
300
320
7,(m41)
Figure 76.
E versus
7'
of 2- Amino- 4,6- Dimethylpyrimìdine
by Method II.
197
Table LXXXIV.
pH
No.
Dissociation Constants of 2- Amino -4
Methylpyr.imidine by Method I.
E at
224
0.50
0.86
1.66
2.37
2.75
3.37
4.34
4.75
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
A=224
5
4
6.27
6.99
8.13
9.14
10.15
10.90
12.00
13.00
14.00
mp,,
mil
13283
13333
13396
13183
13145
12895
11717
12143
12130
12105
12180
12068
12030
12118
12694
12644
13095
17920
E at
288 mµ
E at
299 mv
3947
3972
3997
3922
3910
3922
3734
3860
3885
3860
3872
3860
3860
3872
3860
3847
3872
3847
4724
4699
4662
4599
4474
3985
3133
3108
3070
3C20
2995
3008
3020
3008
3008
2970
3008
3008
x=12800, E=12000, y=13400, pH= 3.60, pKa= 3.47
x=13000, E=15300, y=17900, pH=13.80, pKa=13,85
A=288 mµ,
=299
m9
pKa undeterminable
x= 3000, E= 3900, y= 4700, pH= 3.50, pKa=
a
3..45
224
mp,
288
mp,
299
mp,
16,000
12,000
E
8,000
o
4,000
0
"
I
0
2
1
1
4
1
1
I
1
8
6
i
1
10
I
I
12
pH
Figure
77.
E versus pH of 2-Amino®4- Methylpyrimidine by Method Io
I
14
199
Table LXXXV.
Mmµ)
200
205
210
215
220
224
225
230
235
240
245
250
255
260
265
270
275
280
285
288
290
295
299
300
305
310
315
320
Dissociation Constants of 2- Amino -4Methylpyrimidine by Method II.
E at
E at
pH 1.12
pH 3.37
17447
8723
7362
10426
13234
12872
12447
6851
1915
340
234
319
426
638
936
1362
1915
2596
3340
3702
3936
4404
4489
4511
4128
3383
2489
1298
7519
5865
6454
9524
12406
12531
12155
8459
3321
1128
589
627
789
1053
1404
1867
2406
3070
3634
3922
4010
4160
3985
3922
3358
2506
1654
890
pH 7.00
E
pKa
4894
4149
5532
8298
11170
12234
12340
10191
6064
2234
851
745
1064
1383
1851
2340
2979
3511
3872
3936
3936
3617
3085
2957
2106
1234
553
170
-
3.38
3.50
3.54
3.31
-
3.40
3.66
3.52
3.24
-
3.27
3.27
3.35
3.34
3.41
3.34
3.28
-
3.62
3.58
3.58
3.53
3.49
3.62
pH
13
E
pKa
9085
11596
15319
14511
11234
11702
11766
10106
6064
2234
638
-
702
936
1341
1809
2340
2894
3447
3809
3915
3894
3532
3085
2872
2064
1213
532
149
3.52
3.76
3.49
3.38
3.66
3.52
-
3.21
3.31
3.34
3.37
3.27
-
3.62
3.62
3.60
3.54
3.50
3.63
16,000
200
14,000
12,000
vpH
1,12
pH
3.37
pH
7.00
13.00
pH
10,000
8,000
E
6,000
4,000
2,000
0
I
I
220
200
Figure 78.
I
I
240
I
260
À(m4)
I
280
I
1
300
versus
of 2- Amino- 4- Methylpyrim dine
by Method II.
E
7\
320
201
Table LXXXVI. Dissociation Constants of 4,5,6 Triaminopyrimidine by Method I.
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
pH
0.10
0.61
0.92
1.32
1.52
1.80
2.21
2.62
3.00
3.54
4.05
4.55
5.02
5.56
6.05
6.54
7.01
7.40
7.97
8.57
8.99
9.57
9.99
10.58
10.92
11.50
12.00
12.50
13.00
13.50
14.00
at
210 mµ
E at
215 mµ
12207
11426
10414
9546
9199
9199
9083
9228
9112
9112
9119
9922
10443
12265
13827
15331
15736
16025
15997
15620
15620
16025
16054
15823
15968
15794
15910
15476
11947
8562
5438
14463
13335
11976
10790
10500
10327
10211
10240
10182
10153
10240
10616
10790
11831
12583
13538
13596
13740
13885
13596
13827
13856
13596
13827
13596
13596
13306
13306
11686
8707
5612
E
-
E at
277 mµ
2314
2893
3587
4194
4339
4542
4599
4628
4628
4599
4570
4628
4570
4542
4397
4455
4455
4426
4455
4426
4426
4426
4455
4455
4455
4397
4397
4368
4397
4397
4397
202
Table LXXXVI.
(Continued)
A=210 mµ, x= 9100, E=10600, y=12200, pH= 0.85, pKa= 0088
x= 9100, E=12500, y=16000, pH= 5.65, pKa= 5.66
x= 5400, E=10500, y=15800, pH=13.25, pKa=13 27
2\=215 mµ,
x=10100, E=12300, y=14600, pH= 0.85, pKa= 0.87
x=10100, E=12000, y=13750, pH= 5.70, pKa= 5.66
x= 5600, E= 9700, y=13750, pH=13.40, pKa=13 39
T=277 mµ, x= 2200, E= 3400, y= 4650, pH= 0.85, pKa= 0.87
16,000
12,000
E
8,000
4,000
0
I
I
0
2
I
I
4
I
I
l
I
8
6
I
i
I
I
10
12
pH
Figure 79
E
versus pH of 4,5,6-9Triaminepyrimidine by Method
1.
I
14
204
Table LXXXVII. Dissociation Constants of 4,5,6 Triaminopyrimidine by Method II.
E at
200
205
210
215
220
225
230
235
240
245
250
255
260
265
270
275
277
280
285
290
295
300
305
310
315
320
E at
pH 1.02
pH 5.80
9835
9314
10182
11542
9835
4339
1331
9546
11860
13248
12439
8389
3760
1591
1099
1157
1273
1591
1938
2546
3211
3905
4455
4484
4484
4194
3558
2748
1996
1446
1012
781
839
1041
1475
2112
2893
3616
3905
3905
3905
3905
3876
3789
3442
2922
2343
1736
1157
579
579
289
pH 7.01
E
pKa
10153
13885
15649
13653
8100
3789
1996
1504
1562
1736
2025
2430
2893
3471
4050
4397
4397
4310
3732
2661
1620
839
405
174
58
29
-
5.70
5.69
5.93
-
5.99
5.90
5.90
-
5.90
5.86
5.86
5.75
5.75
pH 13
E
pKa
10963
11137
11426
11281
6943
3182
1793
1475
1591
1793
2112
2459
3008
3529
4108
4426
4397
4310
3616
2546
1446
694
289
®
87
0
0
-
5.80
5.80
5.69
5.87
5.93
-
5.95
5.91
5.91
5.80
5.80
205
.'
14,000
vpH
1A02
pH
J080
pH
7,01
°
pH 13.00
12,000
109000
8,000
6,000
4,,000
2,000
0
,
i
200
,
1
220
1
1
1
,
240
1
1
1
260
1
1
1
1
280
1
1
1
1
1
300
(1711,1)
Fi Tare
80.
versus ì\ of
by Method TI
495,6-Tria.minopyYTmidire
320
206
SUMMARY
Ultraviolet spectroscopic methods lend themselves
only for the determination of those dissociation constants which are the consequence of changes within
a
chromophoric group.
In the case of compounds having a single active
site conjugated with or inherent in the chromophoric
group (see Table IV) the dissociation constants as determined by Methods
I
and II are in fair agreement with
those determined by other methods.
However, Method II
may yield dissociation constants which are suspect with
compounds belonging to this group.
An accurate determination of dissociation constant
by Method II can only be made when the extinction co-
efficients of the protonated and deprotonated forms of
the compound involved in the given dissociation are
known.
In the case of compounds having more than a
single dissociation constant, this would involve the
accurate determination of the extinction coefficients of
intermediate ions
etc.)
(single protonated, double protonated,
in the absence of other absorbing forms.
For this
reason, Method II can only be reasonably reliable in the
measurement of those compounds having not more than one
constant, provided the extinction coefficient of inter-
mediate ion can be determined and the difference in the
207
magnitude of the two constants is such as to make this
possible.
This limits the usefulness of the procedure
almost entirely to compound having single reactive site
in the chromophore.
The compounds involved in these studies fell into
two groups,
those in which the
(a)
T
max.
remained con -
stant while extinction coefficients changed with pH, and
(b)
those in which both extinction coefficients and
changed with pH.
(a)
7
max.
In general, those compounds in group
were in much better agreement with known literature
data of dissociation constants than those of group (b).
The most accurate determination using Method
depends on the choice of
A
I
to be used in making the
extinction coefficient -pH profile.
This choice can
.
best be made after taking this profile in ten mµ intervals over the entire ultraviolet
spectrum, as illustrated
in the case of p- aminobenzoic acid.
In a number of instances dissociation constants were
found for reactions which are best explained on the
hypothesis that
a
proton has been abstracted from an
amino substituent.
R -NH2
`
R NH
+
HA-
The frequency of these observations indicates that
some change in structure of the chromophoric group must
be taking place in the alkaline solution.
208
The failure to get good agreement of dissociation
constants for compounds having three or more active
sites associated with chromophoric group, as measured by
Method
I
and other methods,
indicates the limitations of
these methods.
In general, the dissociation constants as determined
by Method
I
at different regions of the usable spectra
are in fair agreement.
However, deviations up to almost
one order of magnitude have been observed in certain
instances.
209
BIBLIOGRAPHY
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Part II.
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1956, p.
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4.
Beaven, G. H. and E. R. Holiday. Ultraviolet
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1952.
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Uber die Einwirkung von Guanidin
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1930.
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Electrostatic
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1959.
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Brockman, Frank G. and Martin Kilpatrick. Thermodynamic dissociation constants of benzoic acid from
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8
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Quantitative
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210
11.
Evans, P. N.
Condensationspordukte der ß-Diketone
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1893,
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Evans, R. F. et al.
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21,
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APPENDIX
213
ABBREVIATIONS
b = broad peak
C = conductivity method
P =
potentiometric method
S =
spectroscopic method
sh = shoulder of the peak
sm = small peak
T = titration method
pKa -pH
7
= pKa
calculated from E at pH
1,
pH 7,
and intermediate pH
pKa -pH 13 = pKa calculated from E at pH 1, pH 13,
and the same intermediate pH
pKa refers to dissociation constant of the
protonated form of the organic base