CHEM 2311
E5 practice-iv (answers provided)
COPIES OF TABLES 2.7, 9.1, and 9.2 are attached
You may use a calculator on this exam
Atomic Masses: H, 1.008; C, 12.01; N, 14.007; O, 15.999
(i) Which of the following compounds gives an infrared spectrum with peaks at 3300 cm-1 (strong, broad
peak) and 1640 cm-1 (sharp, weak peak), but no strong peak at approximately 1720 cm -1?
O
O
OH
D.
C.
B.
A.
A
B
C
D
OH
(ii) Which of the following is most consistent with a molecule having a molecular ion with m/e of 73?
E. the molecule contains bromine
G. the molecule is an alcohol
F. the molecule contains nitrogen
H. the molecule is an alkene
(iii) Which feature in the 1H NMR spectrum provides information about the number of neighboring
protons of each proton in the compound?
I.. number of signals
K. multiplicity
J. integral
L. chemical shift
O
(iv) Which of the protons in 3-butenal (shown at right) appear at furthest
downfield in the 1H NMR spectrum?
M. i
N. ii
O. iii
P. iv
H2C
i
CH
ii
CH2 C H
iii
iv
(v) What are products of the collision between high energy electrons and methane?
.
Q. CH4– + 2 e–
R. CH3– + H
.
S. CH4+ + 2 e–
T. CH3 + H+ + 2 e–
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
(vi) Which of the following series of peaks appears in the 1H NMR spectrum of 1,4-butanediol
(HOCH2CH2CH2CH2OH)?
U. three singlets
W. a singlet and two triplets
(vii)
13C
How many signals appear further downfield than 100ppm in the
NMR spectrum of 4-methylbenzoic acid (shown at right)?
Y. 4
Z. 5
AA. 6
BB. 8
(viii) Which of the following gives a 13C NMR spectrum consisting of 4 peaks?
CC. 2-methylpentane
EE. 3,3-dimethylpentane
U
V
W
X
V. two triplets and a quartet
X. a singlet, a triplet and a pentet
DD. 2,4-dimethylpentane
FF. hexane
H3CO
COOH
Y
Z
AA
BB
CC
DD
EE
FF
2. (26 points)
(i) (4 points each) Provide a single molecular structure consistent with the following data. The NMR
data is complete. The IR spectra have a number of peaks, only the most relevant are provided.
Compound A: C6H6ClN
1
H NMR:  3.6 (singlet, 2H)
 6.6 (doublet, 2H)
 7.1 (doublet, 2H)
IR: 3520 (broad), 3400 (broad), 3050 cm-1
(and others)
Compound B: C6H11ClO2
1
H NMR:  1.2 (singlet, 9H)
 4.1 (singlet, 2H)
IR: 1740, 1210 cm-1 (and others)
Compound C: C4H9ClO
1
H NMR:  2.1 (pentet, 2H)
 3.3 (singlet, 3H)
 3.4 (triplet, 2H)
 3.7 (triplet, 2H)
IR: peak at 1160 cm-1 (and others)
Compound D:
C3H6O
1
H NMR:  2.7 (pentet, 2H)
 4.7 (triplet, 4H)
IR: peak at 1120 cm-1 (and others)
(ii) (5 points each) Compound E gives a combustion analysis of C 49.41%; H 6.83%
(a) What is the empirical formula of E?
(b) What is the value of SODAR for the smallest possible molecular formula of E?
3. (17 points) Refer to the data provided on the following page. Note that you receive credit for each
part of this answer, the structure you provide in part (n) is only worth 1 point. Each part is graded
independently without reference to other answers
Analysis of Combustion Analysis/Mass Spectrum
(a) What is the molecular formula?
(b) What is the value of SODAR?
.
.
Analysis of IR spectrum (in conjunction with formula)
(c) Which of the following are present? (circle all that are present)
O-H
C-O
C=O
Analysis of the 13C NMR spectrum (in conjunction with IR and SODAR)
(d) How many different types of carbon atoms are there in the molecule:
(e) How many different types of sp3 carbon atoms are there in the molecule:
(f) How many types of aromatic carbons are there?
.
.
.
(g) What structural feature does the peak at 62 ppm suggest?
.
Analysis of 1H NMR spectrum (in conjunction with the formula and IR)
(h) How many different types of hydrogen atom are there in the molecule?
.
(i) What is the ratio of the number of each type of proton,
proceeding from left to right across the spectrum? (i.e., 6:3:1)
(j) Describe the multiplets (i.e., s, d, t, q) at:  3.8 ppm
, and  2.8 ppm
(k) Which of the following are present? (circle all that are present)
Et
iPr
tBu
vinylic H (i.e. an alkene)
(l) How many aromatic hydrogens are there?
aromatic H
.
(m) How many substituents are there on the benzene ring?
Putting it all together
(n) Suggest a single structure for the
molecule that is consistent with all of
the data presented.
.
.
.
INFRARED ABSORPTION VALUES
Group
A. Alkyl
C-H (stretching)
Isopropyl, -CH(CH3)2
tert-butyl, -C(CH3)3
B. Alkenyl
C-H (stretching)
C=C (stretching
R-CH=CH2
APPROXIMATE PROTON CHEMICAL SHIFTS
Frequency Range (cm-1)
Intensity
2583-2962
1380-1385
and 1365-1370
1385-1395
and ~1365
(m-s)
(s)
(s)
(m)
(s)
Type of Proton
1° Alkyl, RCH3
2° Alkyl, RCH2R
3° Alkyl, R3CH
Allyllic, R2C=C-CH3
Chemical Shift (δ, ppm)
0.8-1.0
1.2-1.4
1.4-1.7
1.6-1.9
l
R
Ketone, RCCH3
2.1-2.6
O
Benzylic, ArCH3
Acetylenic, RC≡CH
Alkyl iodide, RCH2I
Ether, ROCH2R
Alcohol, HOCH2R
Alkyl bromide, RCH2Br
Alkyl chloride, RCH2Cl
Ainylic, R2C=CH2
Vinylic, R2C=CH
2.2-2.5
2.5-3.1
3.1-3.3
3.3-3.9
3.3-4.0
3.4-3.6
3.6-3.8
4.6-5.0
5.2-5.7
ll
R2C=CH2
cis-RCH=CHR
trans-RCH=CHR
3010-3095
1620-1680
985-1000
and 905-920
880-900
675-730
960-975
(m)
(v)
(s)
(s)
(s)
(s)
(s)
C. Alkynyl
≡C-H (stretching)
C≡C (stretching)
~3300
2100-2260
(s)
(v)
l
R
Aromatic, Ar-H
Aldehyde, RCH
6.0-9.5
9.5-10.5
ll
D. Aromatic
Ar-H (stretching)
Aromatic substitution type
(C-H out-of-plane bendings)
Monosubstituted
~3030
690-710
730-770
735-770
680-725
and 750-810
800-860
and
o-Disubstituted
m-disubstituted
p-disubstituted
E. Alcohols, Phenols, and Carboxylic Acids
O-H (stretching)
Alcohols, phenols (dilute solution)
Alcohols, phenols (hydrogen bonded)
Carboxylic acids (hydrogen bonded)
(v)
(very s)
(very s)
(s)
(s)
(strong s)
(strong s)
3590-3650
3200-3550
2500-3000
(sharp, v)
(broad, v)
(broad, v)
F. Aldehydes, Ketones, Esters and Carboxylic Acids
C=O (stretching)
1630-1780
Aldehydes
1690-1740
Ketones
1680-1750
Esters
1735-1750
Carboxylic Acids
1710-1780
Amides
1630-1690
(s)
(s)
(s)
(s)
(s)
(s)
G. Amines
N-H
H. Nitriles
C≡N
O
Alcohol hydroxyl, ROH
Amino, RNH2
Phenolic, ArOH
Carboxylic, RCOH
0.5-6.0
1.0-5.0
4.5-7.7
10-13
ll
O
APPROXIMATE CARBON-13 CHEMICAL
SHIFTS
Type of Carbon
1° Alkyl, RCH3
2° Alkyl, RCH2R
3° Alkyl, R3CH
Alkyl halide or amine, C-X
Alcohol or ether, -C-O
Alkyne, , -C≡
Alkene, -C=
Aryl,
Nitriles, -C≡N
O
ll
2200-2500
(m)
Chemical Shift (δ, ppm)
0-40
10-50
15-50
10-65
50-90
60-90
100-170
100-170
120-130
Amides, -C-N-
150-180
O
ll
2220-2260
(m)
Carboxylic acids , esters, -C-O-
160-185
O
ll
s = strong; m = medium, w = weak, v = variable
Aldehydes, ketones, -C-
182-215
E1 Practice-iv,
Empirical Formula: C4H5O
Mass Spec: 100
M+ m/e= 138
IR
50
transmittance
transmittance
100
50
0
13C
13C
0
NMR
•
NMR
Wavenumber / cm-1
3000
2000
1500
Wavenumber / cm-1
1H
1000
1H
NMR
500
NMR