Acid
SbF6 –
SbF6 –
F 3CSO3–
–??
HClO 4
ClO4–
–10
I–
Increasing Acid
Strength
HSO 4–
H 2SO 4
Br –
HBr
H
C
R
H
C
H
O+
Super Acids
all too strong to measure
–10
–9
sulfuric acid
–9
hydrobromic acid
–8
protonated aldehydes
OR'
C
R
O
–7
protonated esters
Cl –
–7
hydrochloric acid
–7
protonated ketones
–6
protonated carboxylic acids
–6
protonated phenols
–3
sulfonic acids
–3
protonated ethers
–2
protonated alcohols
hydronium; H +(aq)
nitric acid
HCl
R'
R'
H
C
R
O+
C
O
OH
OH
H
C
Comment
O
R
OR'
H
C
R
O+
R
Increasing Base
Strength
SO 3 / FSO 3H/SbF 5
HF / SbF5
F 3CSO3H
HI
R
pKa
Conj. Base
R
O+
O
H
O
X
H
O
O
OH
S
O
S
O aka TsOH
H 3C
O
H
+
X
C
O
H 3C
H
+
R
O
R'
R
O
R'
H
+
R
O
H
R
O
H
H 3O+
HNO 3
NO 3–
–1.74
–1.3
HSO 4–
H–F
SO 42–
F–
1.99
3.18
second H of sulfuric acid
hydrofluoric acid
HNO 2
NO 2–
3.3
nitrous acid
–6 to +5
anilines; pKa very sensitive
to ring substituents
H 2O
H
+N H
N H
H
H
X
X
Acid
O
O
C
C
O-H
R
C
H 3C
6.35
7.00
carbonic acid
hydrogen sulfide
9.00
2,4-pentandione
9.24
ammonium ion
4–11
depends on substitution
plain phenol has a pka=10
R–CH–NO 2
10.0
aliphatic nitro
CO3–
10.3
bicarbonate
11.0
ethyl acetoacetate
13.0
diethyl malonate
15.7
water pKa
15.0
cyclopentadiene: World's
Strongest Carbon Acid!!
17.0
amides
16-19
alcohols, ethanol pKa = 16
20-21
alpha H of ketones
25
alpha H of esters
O
O
C
C
H
O
HCO 3–
HS –
H 2CO3
H 2S
O
CH 3
H 3C
O
C
C
C
H
CH 3
H
NH 4+
NH 3
H
X
X
O
R–CH 2 –NO2
O
HCO 3–
O
C
H 3C
O
H
C
EtO
C
H
O
O
C
C
OEt
H 3C
H
O
O
C
OEt
EtO
C
C
O
C
H
C
C
OH –
H
H
H
O
O
H
N
R
H
O
C
C
O
H
C
H
R
C
H
O
RO
C
H
N
R O
R–O–H
R
OEt
H
H–O–H
R
OEt
O
C
H
C
Comment
4.0 to 5.0 carboxylic acids
Increasing Base
Strength
Increasing Acid
Strength
R
pKa
Conj. Base
H
H
O
H
C
C
H
RO
C
H
C H
H
R–CH 2 –CN
R–CH–CN
25
alpha to nitrile
R
R
25
terminal alkynes.
The electrons are in an
sp hybridized orbital
C
C H
C
C
Acid
pKa
Conj. Base
H
N
N
H
X
H
C
C
H
H
C
C
H
H
H
C
H
C
C
36
hydrogen gas is a weak acid
40
amines: NH 3 pKa=38
41
benzyl hydrogens;
conjugated base
H
C
H
H
allyl hydrogens; conjugated
conjugate base.
44
vinyl hydrogens; electrons
in unconjugated sp2 orbital
44
phenyl hydrogens; electrons
in unconjugated sp2 orbital,
not part of aromatic π sextet
46
cyclopropane H; more vinyl
than sp3 hybrid (see below.)
48
methane and hydrogens on
sp3 carbons
52
cyclohexyl; weakest acid on
this table. sp3 conj. base
H
H
H
C
43
H
C
H
H
Increasing Base
Strength
Increasing Acid
Strength
((CH 3)2CH)2N –
H H
H
anilines; pKa Depends on
substitution. Low because it
has a conjugated base.
Plain aniline has pKa =25
H
H
((CH 3)2CH)2NH
H
18–28
X
H2
Comment
H
C
H
C
H
H
H
C
H
H
H 2C
C
H
H
H
H
H
H 2C
H
H
H
H 2C
H
H
C
H
C
H
H 2C
H
C
H
H
H
C
H
H
H
H
H H
H
H
H
H
H H H
H
H
H H
H
H
H
H H H
H
updated 9/6/2016