pKa Data Compiled by R. Williams
pKa Values
INDEX
Inorganic 2 Phenazine 24
Phosphates 3 Pyridine 25
Carboxylic acids 4, 8 Pyrazine 26
Aliphatic 4, 8
Aromatic 7, 8 Quinoline 27
Phenols 9 Quinazoline 27
Alcohols and oxygen acids 10, 11 Quinoxaline 27
Amino Acids 12 Special Nitrogen Compounds 28
Peptides 13 Hydroxylamines 28
Nitrogen Compounds 14 Hydrazines 28
Aliphatic amines 15, 17, 19 Semicarbazones 28
Cyanoamines 16 Amidoximes 28
Anilines 17, 18, 20 Thiols 29
Nucleosides 21 Carbon Acids 30,31
Special Table Heterocycles 22 Indicators 31
Acridine 23 References 32-34
Benzoquinoline 24
Cinnoline 23
Hydantoin 24
Imidazole 24
For complex chelating agents, see also reference 77.
Note. This document was compiled by W.P. Jencks and has been added to by F.H. Westheimer
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 1
pKa Data Compiled by R. Williams
ACIDS
Compound pK Ref. H
3
PO
2
2.0, 2.23* 28
H
2
PO
4
–
7.21* 77
AgOH 3.96 4
HPO
4
_
12.32* 77
Al(OH)
3
11.2 28
H
3
PO
3
2.0 28
As(OH)
3 9.22 28
H
2
PO
3
–
6.58* 77
H
3
AsO
4
2.22, 7.0, 13.0 28
H
4
P
2
O
7
1.52* 77
H
2
AsO
4
–
6.98* 77
H
3
P
2
O
7
–
2.36* 77
HAsO
4
* 11.53* 77
H
2
P
2
O
7
=
6.60* 77
As
2
O
3
0 4
HP
2
O
7
=
9.25* 77H
3
AsO
3
9.22*
H
3
BO
3
9.23* 28 HReO
4
-1.25 30
H
2
B
4
O
7
4.00 34 HSCN 4.00 34
H
2
SeO
3
2.6, 8.3, 2.62* 28
HB
4
O
7
9.00 34
HSeO
3
8.32 77
Be(OH)
2
3.7 4
H
2
SeO
4
Strong, 2.0 28
HBr -9.00 31
HOBr 8.7 28 HSeO
4
2.00 34
HOCl 7.53, 7.46 28, 33
H
3
SiO
3
10.0 34
HClO
2
2.0 28
H
2
SO
3
1.9, 7.0, 1.76* 28, 77
HClO
3
-1.00 28
H
2
SO
4
-3.0, 1.9 28
HClO
4
(70%) -10.00 31
HSO
3
7.21* 77
CH
3
SO
3
H -0.6 31
HSO
4
–
1.99* 77
HCN 9.40 34
H
2
S
2
O
4
1.9 29
H
2
CO
3
6.37, 6.35*, 3.58 34, 32
H
2
Se 3.89* 77
HCO
3
10.33*
HSe
–
11.00* 77
H
2
CrO
4
-0.98 30
H
2
S 7.00* 77
HCrO
4
6.50* 2, 30
HS
–
12.92* 77
HOCN 3.92 34
HSbO
2
11.0 34
HZ 3.17*, 0.59* 77
HTe 5.00 34
H
2
GeO
3
8.59, 12.72 34, 78
H
2
Te 2.64, 11.0 34, 78
Ge(OH)
4
8.68, 12.7 28
H
2
TeO
3
2.7, 8.0 28
HI -10.0 31
Te(OH)
6
6.2, 8.8 28
HOI 11.0 28
H
2
VO
4
–
8.95 30
HIO
3
0.8 28
HVO
4
=
14.4 30
H
4
IO
6
–
6.00 34
H
2
CrO
4
0.74 77
H
5
IO
6
1.64, 1.55, 8.27 34, 28
HOCN 3.73 77
HMnO
4
-2.25 30
HSCN 0.85 77
NH
3
OH* 5.98*
H
3
PO
2
1.07 77
NH
4
* 9.24* 77
H
3
PO
4
2.12* 77
HN
3
4.72* 77
H
2
S
2
O
3
0.60*, 1.72* 77
HNO
2
3.29 28
H
3
AuO
3
13.3, 16.0 78
HNO
3
28
H
3
GaO
3
10.32, 11.7 78
N
2
H
5
+
77
H
5
IO
6
3.29, 6.70, 15.0 78
H
2
N
2
O
2
34
(see above!)
H
2
N
2
O
2
–
34
H
4
V
6
O
17
1.96 78
H
2
OsO
5
34
H
2
NSO
3
H 1.0 80
H
2
O
-1.3
7.99*
7
.05
11.0
12.1
1
4.0*
97
H
3
O
+
97
* Indicates a thermodynamic value.
Pb(OH)
2
0*
6
.48 (10.92)
4 (78)
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 2
PHOSPHATES AND PHOSPHONATES
CF
3
- 1.16, 3.93 57
CCl
3
- 1.63, 4.81 57
Phosphates
NH
3
+
CH
2
- 2.35, 5.9 57
Compound pK Ref.
(
–
OOCCH
2
)
2
NH
+
CH
2
–
--, 5.57 57
Phosphate 1.97, 6.82, 12.5 55
CHCl
2
- 1.14, 5.61 57
Glyceric acid 2-phosphate 3.6, 7.1 53
CH
2
CI- 1.40, 6.30 57
Enolpyruvic acid 3.5, 6.4 53
CH
2
Br- 1.14, 6.52 57
Methyl- 1.54, 6.31 55
(
–
OOCCH
22
NH
+
(CH
2
)
2
- --, 6.54 57
Ethyl- 1.60, 6.62 55
CH
2
I- 1.30, 6.72 57
n-Propyl- 1.88,6.67 55
NH
3
+
CH
2
CH
2
- 2.45, 7.00 57
n-Butyl- 1.80, 6.84 55
Dimethyl- 1.29 55
C
6
H
5
CH=CH- 2.00, 7.1 57
Di-n-propyl 1.59 55
HOCH
2
- 1.91, 7.15 57
Di-n-butyl- 1.72 55
C
6
H
5
NH
2+
(CH
2
)
3
- 2.1, -- 57
Glucose-3- 0.84, 5.67 56
C
6
H
5
NH(CH
2
)
3
- --, 7.17 57
Glucose-4- 0.84, 5.67 56
Br(CH
2
)
2
- 2.25, 7.3 57
α-glycero- 1.40, 6.44 54
CH
3
(CH
2
)
5
CH(COO
–)-
--, 7.5 57
β-glycero- 1.37, 6.34 54
C
6
H
5
CH
2
- 2.3, 7.55 57
3-phosphoglyceric acid 1.42, 3.42 54
NH
3
+
(CH
2
)
4
)- 2.55, 7.55 57
2-phosphoglyceric acid 1.42, 3.55, 7.1
peroxymonophosphoric acid 4.05 69
NH
3
+
(CH
2
)
5
- 2.6, 7.6 57
diphosphoglyceric acid 7.40, 7.99 54
NH
3
+
(CH
2
)
10
- --, 8.00 57
glyceraldehyde- 2.10, 6.75 54
–
OOC(CH
2
)
10
- --, 8.25 57
dioxyacetone- 1.77,6.45 54
(CH
3
)
3
SiCH
2
- 3.22, 8.70 57
hexose di- 1.52, 6.31 54
fructose-6- 0.97, 6.11 54 C
6
H
5
CH
2
- 3.3, 8.4 57
glucose-6- 0.94, 6.11 54
(C
6
H
5
)SC- 3.85, 9.00 57
glucose-1- 1.10, 6.13 54
adenylic acid 3.8?, 6.2? 54
Arylphosphonic acids
inosinic acid 2.4?, 6.4? 54
2X-RC
6
H
3
PO
3
H
2
ADP 2 strong, 6.6 54
X R
ATP 3 strong, 6.6 54
Cl 4-O
2
N 1.12, 6.14 57
pyrophosphoric acid 0.9, 2.0, 6.6, 9.4 54
Br 5-O
2
N (a), 6.14 57
phosphopyruvic acid 3.5, 6.38 54
Cl 5-Cl (a), 6.63 57
creatine phosphate 2.7, 4.5 54
Cl H 1.63, 6.98 57
arginine phosphate 2.8, 4.5, 9.6, 11.2 54
Br H 1.64, 7.00 57
arginine 2.02, 9.0, 12.5 54
Br 5-CH
3
1.81, 7.15 57
amino phosphate (-0.9), 2.8, 8.2 54
Cl 4-NH
2
--, 7.33 57
trimetaphosphate 2.05 77
CH
3
O 4-O
2
N 1.53, 6.96 57
CH
3
O H 2.16, 7.77 57
Phosphonates
CH
3
O 4-O
2
N --, 8.22 57
H
2
O
3
P(CH
2
)
4
PO
3
H
2
<2, 2.75, 7.54, 8.38 57
HO 4-O
2
N 1.22, 5.39 57
H
2
O
3
P(CH
2
)
3
PO
3
H
2
<2, 2.65, 7.34, 8.35 57
O
2
N H 1.45, 6.74 57
H
2
O
3
PCH
2
CH(CH
3
)PO
3
H
2
<2, 2.6, 7.00, 9.27 57
F H 1.64, 6.80 57
H
2
O
3
PCH
2
PO
3
H
2
<2, 2.57, 6.87, 10.33 57
I H 1.74, 7.06 57
Methyl- 2.35 57
NH
2
H --, 7.29 57
Ethyl- 2.43 57
CH
3
H 2.10, 7.68 57
n-propyl- 2.45 57
C
6
H
5
H (a), 8.13 57
isopropyl- 2.55, 7.75 57
HOOC H 1.71, 9.17 57
n-butyl- 2.59, 8.19 57
isobutyl- 2.70, 8.43 57
**These values were obtained in 50% ethanol.
s-butyl- 2.74, 8.48 57
(a) The compounds were not sufficiently soluble.
t-butyl- 2.79, 8.88 57
For graphical plots of a large number of substituted
phosphorus compounds see 83.
neopentyl- 2.84, 8.65 57
1,1 Dimethylpropyl- 2.88, 8.96 57
n-hexyl- 2.6, 7.9 57
triphosphate 8.90, 6.26, 2.30 77
n-dodecyl- --, 8.25 57
tetrametaphosphate 2.74 77
CH
3
(CH
2
)
5
CH(COOH)- 1, -- 57
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 3
fluorophosphate 0.55, 4.8 56
Acetic acids, substituted
Phosphonates (Ref. 2)
H- 4.76* 20
X -H -H -NH
3
+
-NH
3
+
O
2
N- 1.68* 20
X(CH
2
)PO
3
H
2
2.35 7.1 1.85 5.35
(CH
3
)
3
N
+
- 1.83* 20
X(CH
2
)
2
PO
3
H
2
2.45 7.85 2.45 7.00
(CH
3
)
2
NH
+
- 1.95* 20
X(CH
2
)
4
PO
3
H
2
2.55 7.55
CH
3
NH
2
+
- 2.16* 20
X(CH
2
)
5
PO
3 H2
2.6 7.65
NH
3
+
- 2.31* 20
X(CH
2
)
6
PO
2
H
2
2.6 7.9
CH
3
SO
2
- 2.36* 20
X(CH
2
)
10
PO
2
H
2
8.00
NC- 2.43* 20
Phosphines in acetonitrile, see ref. 89.
C
6
H
5
SO
2
- 2.44 20
HO
2
C 2.83* 20
CARBOXYLIC ACIDS
Aliphatic C
6
H
5
SO- 2.66 20
Compound pK Ref.
F- 2.66 20
Acetoacetic 3.58 6
Cl- 2.86* 20
Acetopyruvic 2.61, 7.85 (enol) 6
Br- 2.86 20
Aconitic, trans- 2.80, 4.46 6
Cl
2
- 1.29 20
Betaine 1.84 6
F
2
- 1.24 20
Citric 3.09, 4.75, 5.41 6
Br
3
- 0.66 20
Crotonic 4.69 6
Cl
3
- 0.65 20
Dihydroxyfumaric 1.14 6
F
3
- 0.23 (-0.26) (2) 20
Dethylenediamine- 2.00, 2.67 6
HONC
4
3.01 20
tetraacetic 6.16, 10.26
F
3
C- 3.07* 20
Formic 3.77* 2
N
3
- 3.03 20
Fumaric 3.03, 4.54 6
I- 3.12 20
Glyceric 3.55 6
C
6
H
5
O- 3.12 20
Glycollic 3.82 6
C
2
H
5
O
2
C- 3.35 20
Glyoxylic 3.32 6
C
6
H
5
S- 3.52* 20
Homogentistic 4.40 6
CH
3
O- 3.53 20
α-keto-β-methyl valeric 2.3 6
NCS- 3.58 20
Lactic 3.86 6
CH
3
CO- 3.58* 20
Maleic 1.93, 6.58 6
Malic 3.40, 5.2 6 C
2
H
5
O- 3.60 20
Oxaloacetic (trans-enol) 2.56 6
n-C
3
H
7
O 3.65 20
+(cis-enol) 2.15, 4.06 6
n-C
4
H
9
O 3.66 20
Protocatechuic 4.48 6
sec.-C
4
H
9
O- 3.67 20
Pyruvic 2.50 6
HS- 3.67* 20
Tartaric + 2.99, 4.40 6
i-C
3
H
7
O- 3.69* 20
+ or - 2.89, 4.40 6
CH
3
S- 3.72* 20
meso 3.22, 4.85 6
i-C
3
H
7
S- 3.72* 20
Vinylacetic 4.42 6
C
6
H
5
CH
2
S- 3.73* 20
C
2
H
5
S- 3.74* 20
n-C
3
H
7
S- 3.77* 20
n-C
4
H
9
S- 3.81* 20
HO- 3.83* 20
–
O
3
S- 4.05 20
(C
6
H
5
)
3
CS- 4.30* 20
C
6
H
5
- 4.31* 20
CH
2
-CH- 4.35* 20
* Indicates thermodynamic values.
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 4
Unsaturated acids (25°)
Compound pK ref. Compound pK ref.
trans-CH
3
-CH=CHCO
2
H 4.69* 20 H-CH
2
CH
2
CO
2
H 4.88* 2
cis-CH
3
-CH=CHCO
2
H 4.44* 2 H-CH=CHCO
2
H 4.25* 2
C
6
H
5
-CH
2
CH
2
CO
2
H 4.66* 2 C
6
H
5
CH
2
CH
2
CO
2
H 4.66* 2
trans-C
6
H
5
-CH=CHCO
2
H 4.44* 2 C
6
H
5
CH=CHCO
2
H** 4.44* 2
m-CH
3
OC
6
H
4
CH
2
CH
2
CO
2
H 4.65*
2
C
6
H
5
CH
2
CH
2
CO
2
H 4.66* 2
C
6
H
5
CH=CHCO
2
H** 4.44 2
m-CH
3
OC
6
H
4
CH=CHCO
2
H 4.38* 2
m-ClC
6
H
4
CH=CHCO
2
H** 4.29* 2
m-ClC
6
H
4
CH
2
CH
2
CO
2
H 4.58* 2
Unsaturated acids, Cis- and Trans-
C C
R
2
H
R
1 CO
2
H
C C
R
2
R
1
H
CO
2
H
Cis-Acid Trans-Acid
R
1
R
2
cis-acid trans-acid Ref.
H- H- 4.25* 4.25* 2
CH
3
- H- 4.44* 4.69* 2
Cl- H- 3.32 3.65 2
C
6
H
5
- H- 3.88* 4.44* 2
ClC
6
H
4
H- 3.91 4.41 2
6-BrC
6
H
4
H- 4.02 4.41 2
CH
3
- CH
3
- 4.30 5.02 2
C
6
H
5
- H- 5.26*** 5.58*** 2
2,4,6-(CH
3
)
3
C
6
H
2
- H- 6.12*** 5.70*** 2
C
6
H
5
- CH
3
- 4.98*** 5.98*** 2
Dicarboxylic acids, unsaturated*
Maleic 1.92, 6.23 2 Alicyclic Dicarboxylic acids
Citraconic (Dimethylmaleic acid)
2.29, 6.15 2 cis-Caronic(1,1-dimethylcyclopropane-23-
dicarboxylic acid 2.34*, 8.31* 2Acetylenedicarboxylic 1.73, 4.40 2
∆
1
-tetrahydrophthalic 3.01, 5.34 2
1,2-trans-cyclopropanedicarboxylic
3.65*, 5.13* 2
Bromomaleic 1.45, 4.62 2
trans-caronic 3.82*, 5.32* 2
Bromofumaric 1.46, 3.57 2
1,2-cis-cyclopropane-dicarboxylic
3.33*, 6.47* 2
Chlorofumaric 1.78, 3.81 2
Fumaric 3.02, 4.38 2
Mesaconic (Dimethylfumaric acid)
**trans
3.09, 4.75 2
***in 40% acetone
Phthalic 2.95, 5.41 2
*thermodynamic
Itaconic (1-Propene-2-3-dicarboxylic acid)
3.85, 5.45 2
Chloromaleic 1.72, 3.86 2
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 5
Aliphatic
Alicyclic Dicarboxylic acids
Compound pK Ref Compound pK Ref
1,2-trans-Cyclopropane- cis-Ethyleneoxide-
dicarboxylic 3.65, 5.13 2 dicarboxylic 1.94, 3.92 2
trans-Ethyleneoxide- 1,3-cis-Cyclobutane-
dicarboxylic 1.93, 3.25 2 dicarboxylic 4.03, 5.31 2
1,3-trans -Cyclobutanedi- 1,2-cis-Cyclopentane-
carboxylic 3.81, 5.28 2 dicarboxylic 4.37, 6.51 2
1,2-trans-Cyyclopentane- 1,3-cis-Cyclopentane
dicarboxylic 3.89, 5.91 2 dicarboxylic 4.23, 5.53 2
1,3-trans-Cyclopentane- 1,2-cisCyclohexane-
dicarboxylic 4.40, 5.45 2 dicarboxylic 4.34, 6.76 2
1,2-trans-Cyclohexane- 1,3 -cis-Cyclohexane-
dicarboxylic 4.18, 5.93 2 dicarboxylic 4.10, 5.46 2
1,3-trans-Cyclohexane- 1,4-cis-Cyclohexane
dicarboxylic 4.31, 5.73 2 di-carboxylic 4.44, 5.79 2
1,4-trans-Cyclohexane-
dicarboxylic 4.18, 5.42 2
Dicarboxylic acids*
oxalic 1.23, 4.19 2 Succinic 4.19, 5.48 2
Malonic 2.83, 5.69 2 O-O
’
-Dimethyl- 3.77, 5.94 2
Methyl- 3.05, 5.76 2 (high melting)
Ethyl- 2.99, 5.83 2 O-O
’
-Dimethyl- 3.94, 6.20 2
n-propyl 3.00, 5.84 2 (low melting)
i-propyl- 2.94, 5.88 2 O,O
’
-Diethyl- 3.63, 6.46 2
Dimethyl- 3.17, 6.06 2 (high melting)
Methylethyl- 2.86, 6.41 2 O,O
’
-Diethyl- 3.51, 6.60 2
Diethyl- 2.21, 7.29 2 (low melting)
Ethyl-n-propyl- 2.15, 7.43 2 Tetramethyl- 3.50, 7.28 2
Di-n-propyl- 2.07, 7.51 2
Glutaric 4.34, 5.42 2 Adipic 4.42, 5.41 2
B-Methyl 4.25, 6.22 2 Pimelic 4.48, 5.42 2
B-Ethyl 4.29, 6.33 2 Suberic 4.52, 5.40 2
B-n-Propyl 4.31, 6.39 2 Azelaic 4.55, 5.41 2
B,B-Dimethyl- 3.70, 6.29 2 DL-1:2-Dichlorosuccinic 1.68, 3.18 20
B,B-Methylethyl- 3.62, 6.70 2 meso-1:2-Dichlorosuccinic 1.74, 3.24 20
B,B-Diethyl- 3.62, 7.12 2 DL-1:2-Dibromosuccinic 1.48, ---- 20
B,B-Di-n-propyl 3.69, 7.31 2 meso-1:2-Dibromosuccinic 1.42, 2.97 20
D-Tartaric 3.03, 4.45 20 DL-1:2-Dimethylsuccinic 3.93, 6.00 20
DL-Tartaric 3.03, ---- 20 meso-1:2-Dimethylsuccinic 3.77, 5.36 20
meso-Tartaric 3.29, 4.92 20
*All are thermodynamic values
Aliphatic HO- 6.33 2
Bicyclo[2.2.2]octane-1-carboxylic acids, 4-
substituted
Br- 6.08 2
Lysergic acid, etc.
H- 6.75 2 ergometrine 6.8, -- 2
C
2
H
5
O
2
C- 6.31 2 Dihydroergometrine 7.4, -- 2
β-dihydrolysergol 8.2, -- 2
NC- 5.90 2
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 6
Lysergic acid 7.8, 3.3 2 C
6
H
5
O- 3.53* 3.95* 4.52*
α-dihydrolysergic 8.3, 3.6 2
CH
3
- 3.91* 4.24* 4.34*
ergometrinine 7.3, -- 2
(CH
3
)
2
CH- 4.35*
α-dihydrolysergol 8.3, -- 2
(CH
3
)
3
N
+
- 1.37 3.45 3.43
6-methylergoline 8.85, -- 2
NC- 3.60* 3.55*
isolysergic acid 8.4, 3.4 2
HO
2
C* 2.95* 3.54 3.51
γ-dihydrolysergic 8.6, 3.6 2
F
3
C- 3.79
HO- 2.98* 4.08* 4.58*
I- 2.85* 3.86*
Hydroxycyclohexanecarboxylic acids
Cl- 2.94* 3.83* 3.99*
Cyclohexanecarboxylic 4.90 2
(CH
3
)
3
Si- 4.24* 4.27*
cis-1,2 4.80 2
C
2
H
5
O- 4.21* 4.17* 4.45*
cis-1,3 4.60 2
i-C
3
H
7
O- 4.24* 4.15* 4.68*
cis-1,4 4.84 2
n-C
5
H
11
O- 4.55*
trans-1,2 4.68 2
C
6
H
5
- 3.46*
trans-1,3 4.82 2
CH
3
CH
2
- 3.77 4.35*
trans-1,4 4.68 2
(CH
3
)
3
C- 3.46 4.28 4.40*
–
HO
3
P- 3.78 4.03 3.95
Aromatic
benzene-CO
3
H 4.20* 2
–
O
3
S- 4.15 4.11
Anthracene-1-COOH 3.69 2
H
2
N- 4.98 4.79 4.92
Anthracene-9-COOH 3.65 2
(CH
3
)
2
N- 8.42 5.10 5.03
naphthalene-2-COOH 4.17 2
–
HO
3
As- 4.22
Naphthalene-1-COOH 3.69 2
–
O
2
C- 5.41** 4.60 4.82
CH
3
NH- 5.3 5.10 5.04
Substituted benzoic acids (ref. 2)
COOH
*thermodynamic
for complex chelating agents, see also ref. 84.
see also page 9a for more carboxylic acids.
Benzoic acid o m p
Ortho-substituted benzoic acids
H- 4.20* 4.21*
Benzoic acid pK Ref.
O
2
N- 2.17* 3.45* 3.44
2-CH
3
- 3.91** 2
CH
3
CO-
2-t-C
4
H
9
- 3.46 2
CH
3
SO
2
- 3.64* 3.52*
2,6-(CH
3
)
2
- 3.21 2
CH
3
S-
2,3,4,6-(CH
3
)
4
- 4.00 2
HS-
2,3,5,6-(CH
3
)
4
- 3.52 2
Br- 2.85* 3.81* 4.00*
2-C
2
H
5
- 3.77 2
F- 3.27* 3.87* 4.14*
CH
3
O- 4.09* 4.09* 4.47* 2-C
6
H
5
- 3.46** 2
n-C
3
H
7
O- 4.24* 4.20* 4.46* 2,4,6-(CH
3
)
3
- 3.43 2
n-C
4
H
9
O- 4.25* 4.53* 2,3,4,5-(CH
3
)
4
- 4.22 2
Benzene Polycarboxylic acids Ref. 2
Acid Position of carboxyl pK
I
pK
II
pK
III
pK
IV
pK
V
pK
VI
Benzoic 1 4.17*
Phthalic 1,2 2.98* 5.28*
Isophthalic 1,3 3.46* 4.46*
Terephthalic 1,4 3.51* 4.82*
Hemimellitic 1,2,3 2.80* 4.20* 5.87*
Trimellitic 1,2,4 2.52* 3.84* 5.20*
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 7
Trimesic 1,3,5 3.12* 3.89* 4.70*
Mellophanic 1,2,3,4 2.06* 3.25* 4.73* 6.21*
Prehnitic 1,2,3,5 2.38* 3.51* 4.44* 5.81*
Pyromellitic 1,2,4,5 1.92* 2.87* 4.49* 5.63*
Benzenepentacarboxylic 1,2,3,4,5 1.80* 2.73* 3.97* 5.25* 6.46*
Mellitic 1.2,3,4,5,6 1.40* 2.19* 3.31* 4.78* 5.89* 6.96*
*ionic strength 0.03 2-Methoxyethyliminodiacetic 2.2, 8.96
**thermodynamic 2-Methylthioethyliminodiacetic 2.1, 8.91
oxalic acid* 1.25, 4.14
N-n-propylaminoacetic 2.25, 10.03
Carboxylic Acids Ref. 77 N-2-sulfoethyliminodiacetic 1.92, 2.28, 8.16
Aminomalonic acid* 3.32, 9.83 α-Bromobutyric acid 2.97
N-Butylaminoacetic acid 2.29, 10.07
N-(carbamoylmethyl)-imino-diacetic acid
2.30, 6.60
2-carboxyethyliminodiacetic acid
2.06, 3.69, 9.66
Cyanomethyliminodiacetic 3.06, 4.34
β-carboxymethylaminopropionic 3.61, 9.46
α,β-diaminopropionic acid 1.23, 6.69
α,α-diaminobutyric 1.85, 8.24, 10.44
Diethylaminoacetic 2.04, 10.47
Di-(carboxymethyl)-aminomethyl phosphonic
acid 2.00, 2.25, 5.57, 10.76
Dimethylaminoacetic 2.08, 9.80
N-ethylaminoacetic 2.30, 10.10
α,β-dimercaptosuccinic 2.40, 3.46, 9.44, 11.82 Gluconic* 3.86
β-hydroxybutyric 4.39
Ethylenediamine-N,N-diacetic 5.58, 11.05
α-hydroxybutyric 3.65 β-hydroxypropionic 3.73
N-2-hydroxyethyliminodiacetic 2.2, 8.73 Iminodiacetic* 2.98, 9.89
3-hydroxypropyliminodiacetic 2.06, 9.24 β-iodopropionic* 4.04
Iminodipropionic 4.11, 9.61
N-isopropylaminoacetic 2.36, 10.06
Isobutyric* 4.86
α-mercaptobutyric 3.53
Mandelic acid 3.41
N-methylaminoacetic 2.24, 10.01
2-Mercaptoethyliminodiacetic
Nitrilotriacetic 3.03, 3.07, 10.
-2.14, 8.17, 10.79
2-Phosphonoethyliminodiacetic
Methyliminodiacetic 2.81, 10.18
1.95, 2.45, 6.54, 10.46
*Thermodynamic
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 8
PHENOLS
Compound pK Ref. Compound pK Ref.
Chromotropic acid 5.36, 15.6 6 Resorcinol --, 9.15 (30
o
) 50
o-Methoxyphenol --, 9.93 50 p-Methoxyphenol --, 10.16 50
o-Hydroxybenz- 3-Hydroxyanthran-
aldehyde 7.95 50 ilic acid 10.09, 5.20 51
2-Amino-4,5 dimethyl- 2-Aminophenol
phenol hydrochloride 10.4 5.28 51 hydrochloride 9.99, 4.86 51
4,5-dihydroxybenzene-
1,3 disulphonic acid 7.66 12.6e
Kojic acid 9.40 77
Phenol o m p Phenol o m p
H- 9.95* 9.94* O
2
N- 7.23* 8.35* 7.14*
(CH
3
)
3
N
+
- 7.42 8 8 OCH- 6.79 8.00 7.66
CH
3
SO
2
- 9.33 7.83 NC- 8.61**7.95
CH
3
CO- 9.19 8.05 CH
3
O
2
C- 8.47*
C
2
H
5
O
2
C- 8.50* n-C
4
H
9
O
2
C- 8.47*
C
3
H
5
CH
2
O
2
C- 8.41* I- 9.17*
Br- 8.42* 9.11* 9.34* Cl- 8.48* 9.02* 9.38*
F- 8.81* 9.28* 9.95* CH
3
S- 9.53 9.53
HO- 9.48 9.44 9.96 HOCH
2
- 9.92* 9.83* 9.82*
CH
3
- 10.28*10.08 10.19* C
2
H
5
- 10.2 9.9 10.0
CH
3
O- 9.93 9.65 10.20 H
2
N- 9.71 9.87 10.30
-
O
2
C- 9.94* 9.39*
-
O
3
S- 9.29 9.03
--
O
3
P- 10.2 9.9
--
O
3
As 8.37
C
6
H
5
-
9.93 9.59 9.51 NO- 6.35**
2-Chloro-4-Nitro- 5.42 79
2-Nitro-4-Chloro- 6.46 79
* Thermodynamic
**Reference 52
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 9
ALCOHOLS and other OXYGEN ACIDS
Alcohols
Compound pK Ref. Compound pK Ref.
Choline 13.9 6 C
3
F
7
•CH(C
2
F
5)
•OH 10.48 65
Chloral hydrate 9.66, 11.0 61 (C
3
F
7
)
2
CH•OH 10.52 65
Trifluoroethanol 12.5 62 Carbonium ions
CF
3
CH
2
OH 11.4, 12.43 63
CF
3
CH(OH)CH
3
11.8 63
Triphenylmethanols in H
2
SO
4
HC1O
4
HNO
3
ref
CF
3
CH
2
(CH
3
)3OH 12.43 10 4,4,4-Trimethoxy .82. .82 .80 66
C
3
F
7
CH
2
OH
11.4** 63
4,4’-Dimethoxy -1.24 -1.14 -1.11 66
(C
3
F
7
)
2
CHOH
10.6** 63
-3.40 -3.59 -3.41 66
HCCCH
2
OH
13.55 64
-5.41 -5.67 66
C(CH
2
OH))
4 14.1 64
5.43 5.67 66
HOCH
2
CHOHCH
2
OH
4.4 64 6.35 -5.95 66
HOCH
2
CH
2
OH 14.77 64
CH
3
CCH
2
OH 14.82 64 6.63 -6.89 6.60 66
CH
3
OH 15.54 7.74- 8.01 66
CH
2
=CHCH
2
OH
15.52 9.15- 9.76 66
H
2
O 14.0* (15.74) 97. 64 11.8***
CH
3
CH
2
OH 16 64 11.3***
Substituent effects for ionization of RCH
2
OH
R
CCl-
3
12.24,11.80 64,65
CF3- 12.37 64
CHF
2
CH
2
- 12.74 64
CHCl
2
- 12.89 64 8.45 72
CHEC- 13.55 64 7.40 72
H
2
Cl- 14.31 64 8.80 72
CH
3
CCH
2
- 14.8 64
4-Methoxy
4-Methyl
4
-
Trideuteriomethyl-
3,3’,3”-Trimethyl-
Unsubstituted triphenyl-
methanol-
4,4;,4;-Trichloro-
4
-
Nitro-
CCl
3
CH
2
OH
CF
3
CH
2
OH
Hydroxamic acids
Furo-
Glycine
Hippuro-
isoNicotin 7.85 72
HOCH
2
15.1 p-Methylbenz- 8.90 72
H- 15.5 64 Nicotin- 8.30 72
CH
2
=CH- 15.5 64 Nicotin-methiodide 6.46 72
CH
3
-(extrap) (15.9) 64 m-Nitrobenz- 8.07 72
CF
3
C(CH
3
)
2
OH 11.6 64 Picolin 8.50 72
HOCH
2
CF
2
CH
2
OH 11 64 Pyrimidine-2-carbox- 7.88 72
Primary alcohols=R•CH
2
•OH and Salicyl- 7.43 72
Secondary alcohols in 50% alcohol Tropo- 9.09 72
C
2
F
5
11.35 65
C
4
F
9
11.35 65
C
5
F
11
11.37 65
C
7
F
15
11.35 65 Other oxygen acids
CHF
2
12.00 65 Trimethylamine-n-oxide 4.6 18
CF
2
Cl 11.63 65 Dimethylglyoxime 12.84 77
CHF
2
CF
2
11.34 65 (50% dioxane)
CHF
2
• (CF
2
)
2
11.35 65 O-methyl ether 12.92 77
CF3 • CH2 12.7 65 Tropolone 12a 77
CF
3
• (CH
2
)
2
12.9 65 α-Bromotropolone 6.95
a
77
CF
3
• CHMe • OH 11.28 65 Acetald hydrate 13.48 91
C
3
F
7
• CHMe • OH 11.38 65 Formald hydrate 13.29 91
C
3
F
7
CHEt • OH 11.37 65
C
3
F
7
CHPr • OH 11.37 65
C
3
F
7
• CH(CF
3
) • OH 10.46 65
a
50% dioxane
***50 aquaeous ethanol
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 10
64
64
64
OTHER OXYGEN ACIDS Hydroxamic acids
Aceto- 9.40 68
Compound pK Ref. n-Butyro- 9.48 68
Pyridine oxides n-Butyro- 9.00 68
4-Aminopyridine 1-oxide 3.69 67 p-Methoxybenzo- 9.19 68
4-Dimethylaminopyridine 1-oxide
3.88 67
N-Hydroxyphthalimide 7.00, 6.10 71, 72
Salicylo 7.32 68
4-Dimethylaminopyridine 1-oxide
3.88 67
Benzo- 8.88 68
p-Chlorobenzo- 9.59 68
4-Dimethylamino-1-methoxypyridinium
perchlorate >11 67
α-Naphtho- ~7.7 68
Propiono- 9.46 68
2-Methylaminopyridine 1-oxide 2.61 67
2-Amino-1-methoxypyridinium perchlorate
12.4 67
Oximes
4-Hydroxypyridine 1-oxide 2.45 67
Benzophenone oxime 11.3 18
4-Methoxypyridine 1-oxide 2.05 67
Diethyl ketoxime 12.6 18
1-Methoxypyridi-4-one 2.57 67
Isonitrosoacetylacetone (INAA) 7.4 76
2-Hydroxypyridine 1-oxide -0.8 67
5-Methyl-1,2,3-cyclohexanetrione-1,3-dioxime
8.3 76
2-Ethoxypyridine 1-oxide 1.18 67
1-Methoxypyrid-2-one -1.3
Acetophenone oxime 11.48 18
4-Methylaminopyridine 1-oxide 3.85 67
Acetoxime 11.42 18
4-Amino-1-methoxypyridinium perchlorate
>11 67
Isonitrosoacetone (INA) 8.3 76
Salicyclaldoxime (SA) 9.2 76
2-Aminopyridine 1-oxide 2.67 67
1,2,3-Cyclohexanetrionetrioxime 8.0 76
2-Dimethylaminopyridine 1-oxide
2.27 67
5-Methyl-1,2,3-cyclohexane-trionetrioxime
8.0 76
2-Methylamino-1-methoxypyridinium toluene-
p-sulphonate >11 67
4-Benzyloxypyridine 1-oxide 1.99 67
Oxygen acids
1-Benzyloxypyrid-4-one 2.58 67
sulfinic acids
2-Methoxypyridine 1-oxide 1.23 67
p-Toluene- 1.99 73
1-Benzyloxypyrid-2-one -1.7 67
p-Chlorobenzene- 73
p-Nitrobenzene- 73
Pyridine 1-oxides
p-Bromobenzene- 1.89 73
R pK Ref.
m-Nitrobenzene- 1.88 73
4-CH
3
1.29 47
Benzene- 1.84, 2.16 73
3-CH
3
1.08 47
Peroxyacids
3,4-(CH)
4
1.01 47
Peroxymonosulfuric 9.4 69
3-COOC
4
H
9
0.03 47
Acetic 8.2 70
4-NO
2
-1.7 47
n-Butyric 8.2 70
3-NH
2
1.47 47
Formic 7.1 70
H 0.79 47
Propionic 8.1 70
3-COOH 0.09 47
peroxydiphosphoric 5.18, 7.8 85
4-COOH -0.48 47
peroxymonophosphoric 4.85 90
Peroxides ROOH (Ref. 70)
H CH
3
C
2
H
5
iso-C
3
H
7
tert-C
4
H
9
iso-C
4
H
9
11.6 11.5 11.8 12.1 12.8 12.8
Oximes ref. 93 Pyridine-2-aldoxime heptiodide 8.00
benzoquinoline mon- 6.25 Pyridine-4-aldoxime methiodide 8.50
3-pyridine-1,2-ethanedione-2-oxime
methiodide 7.20
Pyridine-4-aldoxime pentiodide 8.50
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 11
4-Pyridine-1,2-ethanedione-2-oxime
methiodide 7.1
O-Methyltyrosine ethyl ester 7.31 22
octopine 13, 1.36 8.77
6Pyridine-2-aldoxime methiodide 8.0
Phenylglyoxald- 8.3 2.40
Pyridine-4-aldoxime dodeciodide 8.5 Phenylalanine 1.83 9.13 6
Pyridine-3-alkoxime methiodide 9.2 2-Pyrrolidoone-5-carboxylic acid (glucamic
acid) 3.32
Hydroxamic acids ref. 93 Serine 2.21 9.15 6
D-Lysine- 7.93 Threonine 2.63 10.43 6
N-phenylnicotino- 8.00 N-Trimethyl tyrosine 9.75 21
Chloroaceto- 8.40 Tyrosine 10.07, 2.20 9.11
Formo- 8.65 Urocanic acid 5.8 3.5
p-Chlorophenoxyaceto- 8.75 Valine 2.32 9.62 6
p-Hydroxybenzo- 8.93 β-Alanine 3.60 10.19 6
p-Methoxybenzo- 9.00
γ-Aminobutyric acid 4.23 10.43 6
N-Phenylbenzo- 9.15
Arginine 12.48 2.17 9.04 6
o-Aminobenzo- 9.17
Asparagine 2.02 8.8 6
L-Tyrosine 9.20
Azaserine 8.55 6
L-Lysine 7.9
Canavanine 7.40, 9.25 11.50 (?) 6
p-Nitrobenzo- 8.0
Creatine 2.67 11.02 6
p-Aminobenzo- 9.3
Cysteine 10.78 1.71 8.33 6
L-Lacti- 9.3
3,4-Dihydroxyphenylalanine
Propiono- 9.4
9.88, 2.36 8.68 6
Phthalo- 9.4
11.68
Indole-3-aceto- 9.5
Glutamine 2.17 9.13 6
Cyclohexano- 9.7
Histamine 5.0 9.7 6
Hexano- 9.7
β-Hydroxyglutamic 2.09 9.20 6
acid 4.18
Amino Acids
Hydroxyproline 1.92 9.73 6
Compound pK Ref.
Leucine 2.36 9.60 6
-COOH -NH
3
Methionine 2.28 9.21
Alanine 2.35 9.69 6
1-Methylhistidine 6.48, 1.69 8.85 6
α-Aminobutyric acid 2.55 9.60
Norleucine 2.39 9.76 6
α-Aminoisobutyric 2.36 10.21 6
Norvaline 2.36 9.76 6
Argininosuccinic >12, 1.62 9.58 6 Ornithine 1.71 8.69 6
2.70, 4.26 10.76
Aspartic acid 2.09, 3.86 9.82 6 Proline 1.99 10.60 6
Canaline 10.3, 9.20 11.6 (?) 6 Sarcosine 2.23 10.01 6
Creatinine 4.84 9.2 6 Taurine 1.5 8.74 6
Cystine 1.65 7.85 6 Thiolhistidine <1.5, 11.4
2.26 9.85 6 1.84 8.47 6
Diidotyrosine 6.48, 2.12 7.82 6 Tryptophan 2.38 9.39 6
Glutamic acid 2.19, 4.25 9.67 6 Tyrosine ethyl ester 7.33 9.80 22
Glycine 2.34 9.6 6 Peptides
Histidine 6.0, 1.82 9.17
6
Anserine 7.0 2.65 9.5 6
Carnosine 6.83 -- 9.51 6
Hydroxylsine 2.13 8.62 6 Cystinyldiglycine 3.12 6.36 6
9.67 3.12 6.95
Isoleucine 2.36 9.68 6 Glycylglycine 3.06 8.13
Lysine 2.18 8.95 6 Gly-gly-gly 3.26 7.91 23
10.53 Glycylproline 2.84 8.55 6
O-Methyl tyrosine 9.27 21 Aspartyl histi- 2.45 7.98
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 12
dine 6.82 3.02 Gly-gly-gly-gly 3.05 7.75 23
Diglycylcystine 2.71 7.94 6 Lysyl-lysine (L,L) 3.01 7.53 6
Glutathione 9.12 2.12 8.66 6 10.05 11.01
3.53
Compound -COOH -NH
2
-NH
2
-NH
2
-NH
2
Ref.
Gly•Ala (L) or (D) 3.17 8.23 27
Ala•Gly (L) or (D) 3.16 8.24 27
Gly•Ala•Ala (LL) 3.38 8.10 27
Gly•Ala•Ala (LD) 3.30 8.17 27
Ala•Ala•OH (DD) 3.30 8.14 27
Ala•Ala•OH (LD) 3.12 8.30 27
H•Ala•Ala•Ala•OH (3L) 3.39 8.03 27
H•Ala•Ala•Ala•OH (LLD) 3.37 8.05 27
H•Ala-Ala-Ala•OH (LDL) 3.31 8.13 27
H•Ala-Ala-Ala•OH (DLL) 3.37 8.06 27
H-Ala-Ala-Ala•OH (3D) 3.39 8.06 27
H•Ala-Ala-Ala-Ala•OH (4L) 3.42 7.94 27
H•Ala-Ala-Ala-Ala•OH (LLDL) 3.24 7.93 27
H•Ala-Ala-Ala-Ala•OH (LDLL) 3.22 7.99 27
H•Ala-Ala-Ala-Ala•OH (DLLL) 3.42 7.99 27
H•Lys-Ala•OH (LL) 3.22 7.62 10.70 27
H•Lys-Ala•OH (LD) 3.00 7.74 10.63 27
H•Ala-Lys-Ala•OH (3L) 3.15 7.65 10.30 27
H•Ala-Lys-Ala•OH (LDL) 3.33 7.97 10.36 27
H•Ala-Lys-Ala•OH (LLD) 3.29 7.84 10.49 27
H•Ala-Lys-Ala-Ala•OH (4L) 3.58 8.01 10.58 27
H•Ala-Lys-Ala•OH (LDLL) 3.32 8.01 10.37 27
H•Ala-Lys-Ala-Ala-Ala•OH (5L) 3.53 7.75 10.35 27
H•Ala-Lys-Ala-Ala-Ala•OH (LDLLL) 3.30 7.85 10.29 27
H•Lys-Lys•OH (LL) 3.01 7.53 10.05 11.01 27
H•Lys-Lys•OH (LD) 2.85 7.53 9.92 10.98 27
H•Lys-Lys•OH (3L) 3.08 7.34 9.80 10.54 11.32 27
H•Lys-Lys-Lys•OH (LDL) 2.91 7.29 9.79 10.54 11.42 27
H•Lys-Lys-Lys•OH (LDD) 2.94 7.14 9.60 10.38 11.09 27
Compound pK ref.
Glutathione 3.59, 8.75, 9.65 77
Glycylserine 8.23 77
Glycylleucine 8.13 77
Leucylglycine 7.96 77
Glycylisoleucine 7.96 77
Leucylglycylglycine 7.66 77
Glycylphenylalanine 8.28 77
Glycyltyrosine 8.22 77
Benzylglutamic acid 3.49, 4.99 77
Glycyltryptophane 8.04 77
Glutathione, oxidized 3.15, 4.03, 8.57, 9.54 77
Alanylalanine (LL) 3.30 8.14 92
Alanylalanine (LD) 3.12 8.30 92
Lysylalanine (LL) 3.22 7.62 10.70 92
Lysylalanine (LD) 3.00 7.74 10.63 92
Leucyltyrosine (LL) 3.46 7.84 10.09 92
Leucyltyrosine (DL) 3.12 8.38 10.35 92
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 13
Lysyllysine (LD) 2.85 7.53 9.92 92
NITROGEN COMPOUNDS
Aliphatic Amines pK ref.
Ammonia 9.21 1 n-Propyl- 10.53 1
Primary Amines Trimethylsilymethyl- 10.96 1
β-Alanine ester 9.13 1 CH
3
ONH
2
4.60 12
Allylamine- 9.69 2 Allyl- 9.49 1
Benzyl 9.34 1 γ-Amino-n-butyric acid ester 9.71 1
n-Butyl- 10.59 1
sec-Butyl- 10.56 1
t-Butyl- 10.55 1
Cyclohexyl- 10.64 1
Cyclohexylmethyl- 10.49 1
β-difluoroethyl- 7.52 1
Ethanol- 9.50 1
Ethyl 10.63 1
Ethylenedi- 9.98, 7.52 1, 77
Glycine ester 7.75 1
Hydrazine 8.10 1
Hydroxyl- 5.97 1
Isopropyl- 10.63 1
Methoxy- 4.60 1
Methyl- 10.62 1
neo-Pentyl- 10.21 1
Phenylamyl- 10.49 2
δ-Phenylbutyl 10.40 2
β-Phenylethyl- 9.83 1
γ-Phenylpropyl- 10.20 1
Triethylenedi- 8.8* ?
X XNH
3
+
XCH
2
NH
3
+
X(CH
2
)
2
NH
3
+
X(CH
2
)
3
NH
3
+
X(CH
2
)
4
NH
3
+
X(CH
2
)
5
NH
3
+ ref.
H- 9.25* 10.64* 10.67* 10.58* 10.61* 10.63* 2
HF
2
C- 7.52
RO
2
C- 7.75 9.13 9.71 10.15* 10.37 2
HO- 5.96* 9.50*
C
6
H
5
- 4.58* 9.37* 9.83* 10.20* 10.39* 10.49* 2
H
2
N- 8.12* 9.98* 10.65* 10.84* 11.05* 2
H
2
C=CH- 9.69
CH
3
- 10.64* 10.67* 10.58* 10.61* 10.63* 10.64* 2
X -H -NH
3
+
-CO
2
–
-SO
3
–
-PO
3
–
2
X-NH
3
+
9.25* -.88 1 10.25
X(CH
2
)
2
NH
3
+
10.64 9.77 5.75 10.8
X(CH
2
)
2
NH
3
+
10.67 10.19 9.20 10.8
X(CH
2
)
4
NH
3
+
10.61 9.31 10.77 10.65 10.9
X(CH
2
)
5
NH
3
+
10.63 9.74 10.75 10.95 11.0
X(CH
2
)
8
NH
3
+
10.65 10.10
X(CH
2
)
10
NH
3
+
10.64 11.35 11.25
X(CH
2
)
3
NH
3
+
10.58 8.59 10.43 10.05
Secondary amines Di-n-butyl- 11.25 1
Dimethyl- 10.64 1 Diisobutyl- 10.50 1
Di-n-propyl- 11.00 1 α-Ethylpyrroline 7.43 2
Diisopropyl- 11.05 1
α-Benzylpyrroline- 7.08 2
t-Butylcyclohexyl- 11.23 1
2-Methylpiperidine 10.99 2
α-Cyclohexylpyrroline 7.95 2
α-Cyclohexylpyrrolidine 10.80 2
α-(p-Tolyl)pyrroline 7.59 2
α-(p-Tolyl)pyrrolidine 10.01 2
α-Ethylpyrrolidine 10.43 2
N,O-dimethylhydroxylamine 4.75 12
α-Benzylpyrrolidine 10.36 2
Acetanilide +0.61 4
N-methylhydroxylamine 5.96 12 *thermodynamic value
Diethyl- 10.98 1
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 14
Aliphatic Amines Methyl-β-diethylamino-ethyl-sulfide
1,2-Iminoethane 7.98 7
1,2-Dimethyl-∆
2
-pyrroline 11.94 2
cis-2,3-Iminobutane 8.72 7
1-methyl-2-n-butyl-∆
2
-pyrroline 11.90
1,2-Imino-2-methylpropane 8.61 7
1-Ethyl-2-methyl-∆
2
-pyrroline 11.92 2
1,2-Iminobutane 8.29 7
1-n-Butyl-2-methyl-∆
2
-pyrroline 11.90 2
trans-2,3-Iminobutane 8.69 7
1,2-Dimethyl-∆
2
-tetrahydropyridine
11.57 2
Secondary Amines
N-Ethyl derivative of: 1,2-Imino-ethane
7.93 7
Allylmethyl- 10.11 1
Benzylethyl- 9.68 1
Trans-2,3-Iminobutane 9.47 7
Morpholine 8.36 1
Trimethylhydroxylamine 3.65 12
N-Benzoylpiperazine 7.78 1
Dimethylethyl- 9.99 1
Di-sec-butyl- 11.01 1
Triethyl- 10.65 1
N-Methylmethoxyamine 4.75 1
Dimethyl-n-butyl- 10.02 1
Pyrolidine 11.27 1
Dimethyl-isopropyl- 10.30 1
1-Tosylpiperazine 7.39
Dimethyl-t-butyl- 10.52 1
Benzylmethyl- 9.58 1
Tri-n-butyl- 10.89 1
Piperidine 11.22 1
Diallylmethyl- 8.79 1
N-Carbethoxypiperazin 8.28 1
1-n-Propylpiperidine 10.48 2
Dietrimethylsilylmethyl- 11.40 1
10.1 10.1 5
Diallyl- 9.29 1
9.8 -- 5
N-Methylhydroxyl- 5.96 1
1,2-Dimethylpyrrolidine 10.26 2
Trimethyleneimine 11.29 1
1-Methyl-2-n-butylpyrrolidin 10.24 2
Cis-2,6-dimethyl-piperidine 10.92 3
1-Ethyl-2-methylpyrrolidine 10.64 2
1-n-Butyl-2-methylpyrrolidine 10.43 2
1-Ethyl-2-methylpyrrolidine 10.70 2
1,2-Iminobutane 8.18 7
Tertiary amines
cis-2,3-Iminobutane 8.56 7
Trimethyl- 9.76 1
N-dimethylhydroxylamine 5.20 12
Dimethyldiethyl- 10.29 1
Allyldimethyl 8.78 1
Dimethyl-n-propyl- 9.99 1
1,2-Dimethylpiperidine 10.26 2
Dimethyl-isobutyl- 9.91 1
1-Ethyl-2-methyl-∆
2
-tetrahydropyridine
11.57 2
Dimethyl-sec-butyl- 10.40 1
Tri-n-propyl- 10.65 1
Triallyl- 8.31 1
N-Allylpiperidine 9.69 2
1-Diethylamino-hexane-thiol-(6)
Cyanoamines 2-Amino-2-cyanopropane 5.3 9
N-piperidine-CH
2
CN 4.55 8 β-Isopropylaminopropionitrile 8.0 9
Et
2
NCN -2.0 8 β-Diethylaminopropionitrile 7.6 9
Et
2
N(CH
2
)
2
CN 7.65 8 Et
2
NCH
2
CN 4.55 8
Et
2
N(CH
2
)
4
CN 10.08 8 Et
2
N(CH
2
)
3
CN 9.29 8
Et
2
NC(CH
3
)
2
CN 9.13 8 Et
2
N(CH
2
)
5
CN 10.46 8
EtN(CH
2
CN)
2
-0.6 8 HN(CH
2
CN)
2
0.2 8
EtN(CH
2
CH
2
CN)
2
4.55 8 HN(CH
2
CH
2
CN)
2
5.26 8
H
2
NCH
2
CN 5.34 8 N(CH
2
CH
2
CN)
3
1.1 8
N-Amphetamine-(CH
2
)
2
-CN 7.23 8 N-piperidine-C(CH
3
)
2
CN 9.22 8
N-Norcodeine-(CH
2
)
2
CN 5.68 8 N-Methamphetamine-(CH
2
)
2
CN 6.95 8
Dimethylcyanimide 1.2 9 Methyl cyanamide 1.2 9
Diethylcyanimide 1.2 9 Ethyl cyanamide 1.2 9
Aminoacetonitrile 5.3 9 Cyanamide 1.1 9
Diethylaminoacetonitrile 4.5 9 Dimethylaminoacetonitrile 4.2 9
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 15
β-Aminopropionitrile 7.7 9 CF
3
CH
2
NHCH
3
6.05 10
β-Dimethylaminopropionitrile 7.0 9
Phenylethylamines
β,β"-Dicyanodiethylamine 5.2 9
2-phenylethylamine 9.78 11
For complex chelating agents of aliphatic amines,
see also ref. 77.
N-methyl-2-(3,4-dihydroxyphenyl)-
ethylamine 8.78 11
N-methyl-2-phenyl 10.31 11
Fluoro-substituted amines
Epinephrine 8.55 11
CF
3
CH
2
NH
2
5.7 10
Arterenol 8.55 11
CF
3
CH
2
N(CH
3
)
2
4.75 10
R
2
R
1
CHCH
2
NHR
4
R
3
ref. 11
R
1
R
2
R
3
R
4
pK
H H H H 9.78
H H OH H 8.90
H OH OH H 8.81
OH H OH H 8.67
H OH H H 9.22
OH OH H H 8.93
OH OH OH H 8.58
H H H CH
3
10.31
H H OH CH
3
9.31
H OH OH CH
2
8.62
OH H OH CH
3
8.89
H OH H CH
3
9.36
OH OH H CH
3
8.78
OH OH OH CH
3
8.55
Ring amines and imines (in 80% methyl cellosolve) (ref. 2)
Pentamethylene 9.99 Cyclotridecyl 9.63
Hexamethylene 10.00 Cyclotetradecyl 9.54
Heptamethylene 9.77 Cyclopentadecyl 9.54
Octamethylene 9.39 Cycloheptadecyl 9.57
Nonamethylene 9.14 Cyclooctadecyl 9.54
Decamethylene 9.04
Undecamethylene 9.14 Amines other
Dodecamethylene 9.31 Dimeoone 5.23 18
Tridecamethylene 9.35 Phthalimide 8.30 18
Tetradecamethylene 9.35 Nitrourea 4.57 18
Hexadecamethylene 9.29 Nitrourethane 3.28 18
Heptadecamethylene 9.27 Diphenylthiocarbazone 4.5 6
Cyclohexyl 9.82 β,β,β"-Triaminotriethylamine
Cycloheptyl 9.99
8.42, 9.44, 10.13 87
Cyclooctyl
Cyclononyl 9.95
Anilines Ref. 2
Cyclodecyl 9.85
Monosubstituted
Cycloundecyl 9.71
Substituent o m p
Cyclododecyl 9.62
H- 4.62* 4.64* 4.58*
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 16
(CH
3
)
3
N
+
- 2.26 2.51
p-(CH
3
)
3
C- 4.65
m-Br- 3.08
CH
3
O
2
C- 2.16 3.56 2.30
m-Cl- 3.09
CH
3
SO
2
- 2.68* 1.48
p-F- 4.01
CH
3
S- 4.05 4.40
p-(CH
3
)
3
Si- 3.99
Br- 2.60* 3.51* 3.91*
p-CH
3
O- 5.14, 5.16
F- 2.96* 3.38* 4.52*
CH
3
O- 4.49* 4.20* 5.29*
C
6
H
5
- 3.78* 4.18 4.27*
(CH
3
)
3
C- 3.78
–
O
3
S- 3.80 3.32
H
3
N
+
1.3 2.65 3.29
O
2
N- -0.28* 2.45* 0.98*, 1.11*
HO
2
C- 2.04 3.05 2.32
C
2
H
5
O
2
C- 2.10 2.38
F
3
C- 3.49* 2.57*
HO- 4.72 4.17 5.50
Cl- 2.62* 3.32* 3.81*
(CH
3
)
3
Si- 4.64* 4.36*
C
2
H
5
O- 4.47* 4.17* 5.25*
CH
3
- 4.38* 4.67* 5.07*
–
HO
3
As 3.77 4.05 4.05
H
2
N- 4.47 4.88 6.08
*Thermodynamic
Dimethyl
H 5.07 52
m-NO
2
2.63 52
m-CN 2.97 52
p-NO
2
0.61 52
p-CN 1.78 52
p-NO 4.54 52
Dimethyl (in 50% ethanol)
Substituent XC
6
H
4
N(CH
3
)
2
ref. 2
H- 4.21, 4.09
m-CH
3
4.66
p-C
2
H
5
- 4.69
o-(CH
3
)
2
CH- 5.05
p-CH
3
CH
2
CH
2
CH
2
- 4.62
o-(CH
3
)
3
C- 4.26
p-I- 3.43, 2.73
p-Br- 3.52, 2.82
p-Cl- 3.33
m-(CH
3
)
3
Si- 4.41
o-CH
3
O- 5.49
o-CH
3
5.15, 5.07
p-CH
3
4.94
p-CH
3
CH
2
CH
2
- 4.43
p-(CH
3
)
2
CH- 4.77
p-(CH
3
)
2
CHCH
2
- 4.19
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 17
Ortho-substituted anilines (in 50% ethanol) 1-NH
2
-8-NO
2
- 2.79
H- 4.25
1-NH
2
-8-SO
3
- 1.71
2-CH
3
- 3.98, 4.09
1-NH
2
-3-SO
3
- 3.20*
2,3-(CH
3
)
2
- 4.42
1-NH
2
-4-SO
3
- 2.81*
2,4-(CH
3
)
2
- 4.61
1-NH
2
-5-SO
3
- 3.69*
2,5-(CH
3
)
2
- 4.17, 4.23
1-NH
2
-6-SO
3
- 3.80*
2,6-(CH
3
)
2
- 3.42, 3.49
1-NH
2
-7-SO
3
- 3.66
3,5-(CH
3
)
2
- 4.48
1-NH
2
-8-SO
3
- 5.03*
2-CH
3
- 4.09
2-NH
2
- 4.11*
2-(CH
3
)
2
CH- 4.06
2-NH
2
-1-NO
2
- -1.0
2-(CH
3
)
2
C- 3.38
2-NH
2
-3-NO
2
- 2.93
2,6-(CH
3
)
2
-4-(CH
3
)
3
C- 3.88
2-NH
2
-4-NO
2
- 2.63
2,4-(CH
3
)
2
-6-(CH
3
)
3
- 3.43
2-NH
2
-5-NO
2
- 3.16
2-CH
3
-4,6-(CH
3
)
3
C- 3.31
2-NH
2
-6-NO
2
- 2.75
2,4,6-[(CH
3
)
3
C
3
]- <2
2-NH
2
-7-NO
2
- 3.13
2-NH
2
-8-NO
2
- 2.86
Substituted Naphthylamines
2-NH
2
-1-SO
3
- 2.35
1-NH
2
- 3.92*
2-NH
2
-3-SO
3
- --
1-NH
2
-2-NO
2
- -1.6
2-NH
2
-4-SO
3
- 3.70
1-NH
2
-3-NO
2
- 2.22
2-NH
2
-5-SO
3
- 3.96*
1-NH
2
-4-NO
2
- 0.54
2-NH
2
-6-SO
3
- 3.74*
1-NH
2
-5-NO
2
- 2.80
2-NH
2
-7-SO
3
- 3.95*
1-NH
2
-6-NO
2
- 3.15
2-NH
2
-8-SO
3
- 3.89*
1-NH
2
-7-NO
2
- 2.83
N-substituted anilines*
R C
6
H
5
NHR C
6
H
5
N(CH
3
)R C
6
H
5
NR
2
2-CH
3
C
6
H
4
NHR 2-CH
3
C
6
H
4
NR
2
H- 4.58 4.85 4.58 4.39 4.39
CH
3
- 4.85 5.06 5.06 4.59 5.86
C
2
H
5
- 5.11 5.98 6.56 4.92 7.18
n-C
3
H
7
- 5.02 -- 5.59 --
n-C
4
H
9
- 4.95 -- ~5.7 --
i-C
4
H
9
- -- 5.20 -- --
sec-C
4
H
9
- -- 6.04 -- --
t-C
6
H
12
- 6.30 -- -- --
Cyclopentyl- 5.30 6.71 -- 5.07
Cyclohexyl- 5.60 6.35 -- 5.34
t-C
4
H
9
- 6.95 7.52 -- 6.49
*Thermodynamic
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 18
AMINES ref. 77 Secondary amines
N-Butylaminoacetic acid 2.29, 10.07
Primary amines N,N'-Diethylethylenediamine 7.70, 10.46
2-aminoethylsulphonic acid 9.08 2,2'-dihydroxydiethylamine 9.00
Aminomalonic acid 3.32, 9.83 N,N'-di-n-propylethylenediamine 8.14, 10.97
N-n-butylethylenediamine 7.53, 10.30 Ethylenediamine-N,N'-diacetic acid 6.42, 9.46
2,3-diaminobutane, meso 6.92, 9.97 Iminodipropionic acid 4.11, 9.61
2,3-diaminobutane, racemic 6.91, 10.00 Piperazine 5.68, 9.82
2,2'-diaminodiethyl sulfide 8.84, 9.64 β-carboxymethylaminopropionic acid
1,3-diamino-2,2-dimethylpropane 8.18, 10.22
3.61, 9.46
N,N'-Di-(2-aminoethyl)-ethylenediamine
3.32, 6.67, 9.20, 9.92
N,N'-Dimethylethylenediamine 7.40, 10.16
N-ethylaminoacetic acid 2.30, 10.10
1,2-diamino-2-methylpropane 6.79, 10.00
Iminodiacetic acid 2.98, 9.89
1,3-Diaminopropan-2-ol 8.23, 9.68
N-isopropylaminoacetic acid 2.36, 10.06
N,N'-Diglycyethylenediamine 7.63, 8.35
N-n-propylaminoacetic acid 2.28, 10.03
Ethylenediamine-N,N-diacetic acid 5.58, 11.05
Furfurylamine 8.89
Tertiary amines
2-(2-hydroxypropylamino)-ethylamine 6.94,
9.86
4-(2-aminoethyl)morpholine 4.84, 9.45
Di-(2-hydroxyethyl)aminoacetic acid 8.08
2-(3-hydroxypropylamino)ethylamine
Hexamethylenetetramine 5.13
6.78, 9.76
Methyliminodiacetic acid 2.81, 10.18
N-Methylaminoacetic acid 2.24, 10.01
Diethylaminoacetic acid 2.04, 10.47
Methyl-α-amino-β-mercaptoproionate 6.56,
8.99
Dimethylaminoacetic acid 2.08, 9.80
N-2-hydroxyethyliminodiacetic acid 2.2, 8.73
N-n-propylethylenediamine 7.54, 10.34 Triethylenediamine 4.18, 8.19
1,2,3-triaminopropane 3.72, 7.95, 9.59
Tris-(hydroxymethyl)-aminomethane 8.10 Ref. 1
2-amino-2'-hydroxydiethyl sulfide 9.04 Diallylmethyl 8.79
N-(carbamoylmethyl)-iminodiacetic acid
2.30, 6.60
Benzyldimethyl 8.93
N-Allylpiperidine 9.68
2,2'-diaminodiethylamine 3.58, 8.86, 9.65 N-Allylmorpholine 7.05
2,3-diamino-2,3-dimethylbutane 6.56, 10.13 Propargyldimethyl 7.05
3,3'-diaminodi-n-propylamine 8.02,9.70, 10.7 Propargylethyldimethyl 8.88
1,2-Di-(2-aminoethylthio)ethane 8.43, 9.32 N-Methylmorpholine 7.41
1,2-diaminopropane 7.13, 10.00 N-Methylpyrrolidine 10.46
N,N-diethylethylenediamine 7.07, 10.02 N,N-Dimethylhydroxylamine 5.20
N,N-dimethylethylenediamine 6.63, 9.53 Allyldimethyl 8.73
N-Ethylethylenediamine 7.63, 10.56 Benzyldiethyl 9.48
N-(2-hydroxyethyl)-ethylenediamine N-Ethylpiperidine 10.40
6.83, 9.82 N-Ethylmorpholine 7.70
N-isopropylethylenediamine 7.70, 10.62 Propargymethyldimethyl 8.33
2-Methoxyethylamine 9.20 N-Methylpiperidine 10.08
Mercaptoethylamine 8.27, 10.53 N-Methyltrimethyleneimine 10.40
N-Methylethylenediamine 7.56, 10.40 Triethanolamine 7.77
2-Methylthioethylamine 9.18 N,N-Dimethylmethoxyamine 3.65
2-thienylmethylamine 8.92
Triaminotriethylamine 8.56, 9.59,
10.29
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 19
Ref. 5 Methyl-[β-diethylamino-ethyl]sulfide 9.8
N-Dimethyl-cysteamine 7.95, 10.7
N-Diethyl-cysteamine 7.8, 10.75
N-Dipropyl-cysteamine 8.00, 10.8
N-β-Mercaptoethyl-piperidine 7.95, 11.05
N-β-Mercaptoethyl-morpholine 6.65, 9.8
1-Diethylamino-propan- (3) 8.0, 10.5
1-Diethylamino-butan- (4) 10.1
1-Diethylamino-hexan- (6) 10.1
ANILINES (Ref. 88)
m-Substituted anilines
m-C
2
H
5
4.70 m-CH(CH
3
)
2
4.67
-C(CH
3
)
3
4.66 3,5-(CH
3
)
2
4.74
3,5-[C(CH
3
)
3
]
2
4.97 m-COCH
3
3.56
m-CN 2.76 3-Cl,5-OCH
3
3.10
3-OCH
3
.5-NO
2
2.11 3,5-(OCH
3
)
2
3.82
3,5-Br
2
2.34
NAPHTHALAMINES (reference 88)
substituted naphthalamines
2-naphthalamine X 4.16 2-naphthalamine X
1-NH
2
,3-X NO
2
2.07 2-NH
2
,4-X NO
2
2.43
CN 2.26 CN 2.66
Cl 2.66 Cl 3.38
Br 2.67 Br 3.40
I 2.82 I 3.41
COOCH
3
3.12 COOCH
3
3.38
OCH
3
3.26 OCH
3
4.05
OH 3.30 1-NH
2
,6-X NO
2
2.89
CH
3
3.96 Cl 3.48
Cl 2.71 OCH
3
3.90
2-NH
2
,5-X NO
2
3.01 OH 3.97
OH 4.07 2-NH
2
,7-X NO
2
3.10
1-NH
2
,5-X NO
2
2.73 Cl 3.71
OH 3.96 OCH
3
4.19
Cl 3.34 OH 4.25
NH
2
4.21 NH
2
4.66
1-NH
2
,7-X NO
2
2.55 2-NH
2
,6-X NO
2
2.62
Cl 3.48 OCH
3
4.64
OCH
3
4.07 2-NH
2
,8-X NO
2
2.73
OH 4.20 1-NH
2
,4-X NO
2
0.54
1-NH
2
,2-X NO
2
-1.74 Br 3.21
1-X,2-NH
2
NO
2
-0.85 2-NH
2
,3-X NO
2
1.48
1-NH
2
,8-X NO
2
2.79
,
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 20
Anilines (in 50% ethanol)
5'-IMP 8.9, 1.54, 6.04 6
Unhindered pK ref.
5-Methylcytosine 4.6, 12.4 6
Aniline 4.19 40
5-Methylcytosine deoxyriboside 5'-phosphate
4.4 6
p-Aminodiphenyl 3.81 40
2-Naphthylamine 3.77 40
3-Methyluracil 9.75 37
3-Phenanthrylamine 3.59 40
3-Methylxanthine 8.5 (8.1), 11.3 38
m-Aminodiphenyl 3.82 40
Adenosine 3.63 6
2-Aminofluorene 4.21 40
" 3.3, 12.5 35
2-Phenanthrylamine 3.60 40
5'-AMP 3.3, 6.1 36
2-Anthrylamine 3.40 40
3.74, 6.2-6.4 6
Hindered
Barbituric acid 3.9, 12.5 37
o-Aminodiphenyl 3.03 40
Cytidine 4.11 6
peri
" 4.22, 12.5 35
1-Naphthylamine 3.40 40
2'-CMP 4.3-4.4, 6.19* 6
9-Phenanthrylamine 3.19 40
5'-CMP 4.5, 6.3 6
3-Aminopyrene 2.91 40
CTP 4.6, 6.4 6
1-Phenanthrylamine 3.23 40
2,6-Diaminopurine 5.09, 10.77 6
1-Anthrylamine 3.22 40
Isoguanine 4.51, 8.99 6
Guanosine (deoxy) 1.6-2.2, 9.16-9.5 6
meso
GMP (2' + 3') 2.3, 9.36, 0.7, 5.9 6
9-Anthrylamine 2.7 40
5'-GMP (deoxy) 2.9, 9.7, 6.4 6
o-Aminophenols
GTP 3.3, 9.3, 6.5 6
3-Hydroxyanthranilic acid 10.09, 5.20 51
Inosine 1.2, 8.9 6
2-Aminophenol hydrochloride
" 8.75, 12.5 6
9.99, 4.86 51
5-Methylcytosine deoxyribosideIndicators
p-Aminoazobenzene 2.82, 2.76 60
4.5, 13.0 6
4-Chloro-2-nitroaniline -1.02, -1.03 60
1-Methyluracil 9.95 37
4,6-Dichloro-2-nitroaniline -3.61, -3.32 60
1-Methylxanthine 7.7, 12.05 38
6-Bromo-2,4-dinitroaniline -6.64, -6.71
7-Methylxanthine 8.5 (8.3) 38
2-Amino-4,5-dimethylphenol hydrochloride 10.40,
5.28 51
9-Methylxanthine 6.3 38
Purine 2.52, 8.90 37
N,N-Dimethyl-2,4-dinitroaniline -1.00, -- 60
Thymidine 9.8 6
p-Nitrodiphenylamine
5'-TMP 10.0, 1.6, 6.5 6
-2.4 to -2.9, -2.50 60
Uracil deoxyriboside 9.3 6
4-Methyl-2, dinitroaniline -3.96, -4.44 60
5'-UMP 9.5, 6.4 6
Heterocyclics
UTP 9.5, 6.6 6
Nucleosides, etc.
Uridine 9.25 6
Adenine 4.15, 9.80 6
" 9.17, 12.5 35
2'-AMP 3.81, 6.17 6
Xanthosine 0, 5.5, 13.0 6
3'-AMP 3.74, 5.92 6
Orotic acid 2.8, 9.45, 13 6
ADP 3.95, 6.3 36
Pyrimidine 1.30 37
ATP 4.00 (4.1), 6.5 36
Thymine 0, 9.9, 713.0 6
Barbital 7.85, 12.7 37
Uracil .5, 9.5, 13.0 6
Cytosine 4.45, 12.2 6
UMP (2' + 3') 9.43, 1.02, 5.88 6
Cytosine (deoxy) 4.25 6
UDP 9.4, 6.5 6
3' CMP 4.16-4.31, 6.04 6
Uric acid 5.4, 10.3 6
CDP 4.44 6
Xanthine 0.8, 7.44, 11.12 6
CDP, (deoxy) 4.8, 6.6 6
" 7.2 38
Guanine 3.3, 9.2, 12.3 6
Guanosine 2.2, 9.5 6
" 1.6, 9.16, 12.5 35
5'-GMP 2.4, 9.4, 6.1 6
GDP 2.9, 9.6, 6.3 6
Hypoxanthine 1.98, 8.94, 12.10 6
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 21
Heterocyclic Bases (Ref. 2)
N
N
N
N
N
N
N
N
N N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
Pyridine 5.14*
pK (20°)
2
3
5
4
6
7
8
Quinoline 4.85*
Isoquinoline 5.14* Benzoquinoline 5.05*
2
3
456
7
8
9
10
1
Acridine 5.60
5,6-Benzoquinoline
5.15*
7,8-Benzoquinoline
4.25*
Phenanthridine 3.30
a
2,3-Benzacridine 4.52
a
3,4-Benzacridine 4.70*
1,2-Benzacridine 3.45
a
Pyridazine 2.10*
Pyrimidine 1.10*
Pyrazine 0.37*
Cinnoline 2.64*
Phthalazine 3.39*
Quinazoline 3.31*
Quinoxaline 0.6*
a
50% EtOH
Heterocyclics 3-Hydroxy 8.81, 5.52 39
Aureomycin 3.30, 7.44, 9.27 77 5-Hydroxy (acridone) --f, -0.32 39
Iridine --, 5.62 39 5-Methoxy --, 7 39
Acridine 1-- 2-- 3-- 4-- 5-- 9-- Ref. 2
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 22
H-- 5.60* 4.11
a
H
2
N-- 4.40* 8.04* 5.88* 6.04* 9.99*
3.59
a
7.61
a
5.03
a
5.50
a
9.45
a
HO-- 4.18
a
4.86
a
5.52
39
4.45
a
-.32
39
10.7
a
9.9
a
8.81
39
9.4* >12
CH
3
-- 3.95
a
4.60
a
4.70
a
H
2
K-(1-CH
3
--)-- 4.79
a
9.73
s
3.22
a
1,9-(CH
3
)
2
-- 2.88
a
a
50% ethanol; ref. 39
8-amino-1,2-benzacridine 6.72 40 α,α'-dipyridyl 4.43 6
2-amino-4-methyl-5,6-benzoquinoline 7.14
40
4-amino- 8.75
a
19
4-amino-2-methyl- 9.45
a
19
3-amino-6,7-benzoquinoline 4.78 40
4-amino-2-methyl-8-chloro- 5.95
a
19
8-amino-3,4-benzacridine 7.42 40
8-chloro- 2.5
a
19
1'-amino-5,6-benzoquinoline 5.03 40
3,4-diamino- 8.15
a
19
4'-amino-5,6-benzoquinoline 5.20 40
3-amino- 4.78, 3.73
a
19
2-amino-4-methyl-7,8,benzoquinoline
7,8-benzquinoline 4.25, 3.15
a
19
6.74 40
4-amino- 7.68
a
19
6,7-benzoquinoline 5.05, 3.84
a
19
4-amino-2-methyl- 7.96
a
19
5,6-benzoquinoline 5.15, 3.90
a
19
2-amino-4-methyl- 6.74, 6.02
a
19
4-amino- 7.99
a
19
6-amino-2-methyl- 5.23
a
19
2-methyl- 4.44
a
19
1'-amino-2-methyl- 4.75
a
19
4-amino-2-methyl- 8.45
a
19
3,4-benzacridine 4.70, 4.16
a
19
2-amino-4-methyl- 7.14, 6.51
a
19
5-amino 8.41
a
19
4'-amino- 5.20, 4.10
a
19
7-amino- 5.03
a
19
3'-amino- 4.02
a
19
8-amino- 7.42 (6.51)
a
19
1'-amino- 5.03 19
8-acetamido- 4.48
a
19
2',4'-diamino- 4.91
a
19
8-dimethylamino- 7.31, 6.99 19
Benziminazole 5.53 19
1,2-benzacridine 3.45
a
19
2-amino- 7.54 19
5-amino- 8.13
a
19
Benztriazole 1.6 19
7-amino 4.05
a
19
Benzthiazole 1.2, 0.1
a
19
8-amino- 6.72, 5.97
a
19
2-amino- 4.51 19
4',5-diamino- 8.44
a
19benzoxazole (decomp.) 19
2-amino- 3.73 19 Cinnoline --, 0.21 39
2,3-benzacridine 4.52
a
19
3-hydroxy 8.64, 0.21 39
5-hydroxy 7.40, 1.92 39
5-amino- 9.72
a
19
7-hydroxy 7.56, 3.31 39
5-acetamido- 4.56
a
19
4-methoxy --, 3.21 39
7-amino- 5.38
a
19
5-amino-6:7:8:9-tetrahydro- 9.66
a
19
Heterocyclics
Caffeine 0.61 4
o,o'-dipyridyl 4.43 6
cinchonine 7.2 4
hydantoin 9.16 42
Cinnoline 2.70 19
5-isopropyl-2-thio- 8.70 42
4-amino- 6.84 19
5,5-pentamethylene2-thio 8.79 42
Cocaine 7.6 4
3,5,5-trimethyl-2-thio 10.80 42
Cinnoline 4-hydroxy 9.27, 0.35 39
3-methyl-5,5-pentamethylene-2-thio-
6-hydroxy 7.52, 3.65 39
11.23 42
-hydroxy 8.20, 2.74 39
Imidazoles
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 23
2-Methylimidazole 7.75 43 Histidine methylester
5.2 (NH
2
7.1)
43
N-Acetylhistidine 7.05 43
2-Methyl-4-hydroxy-aminobenz- 6.65 43
4-Hydroxymethyl- 6.45 43
2-Methyl-4-hydroxy-6-nitro-benzimidazole
3.9 43
2-Methylbenz- 6.1 43
Histamine 6.0 43
4-Hydroxy-6-Nitrobenz- 3.05 43
4-Hydroxy-6-aminobenz- 5.9 43
b
2-Hydroxymethylnaphth(1,2)-
4-Hydroxybenz- 5.3 (OH 9.5)43
4.44, 12.23 86
4-Methoxybenz- 5.1 43 b
2-Hydroxymethylnaphth(2,3)-
4-Bromo- 3.7 43
4.50, 12.23 86
6-Nitrobenz- 3.05, 10.6 43
4-Hydroxy- 4.80, 8.68 44
4-Nitro- 1.5, 9.1 43
1-Amino- 7.62 40
isoQuinolines
4-Amino- 6.28 40
1-Hydroxy- -1.2 44
6-Amino- 7.17 40
5-Hydroxy 5.40, 8.45 44
8-Amino- 6.06 40
3-Amino- 5.05 40
7-Hydroxy- 5.70 40
5-Amino- 5.59 40
1-Methoxy- 3.05 44
Amino- 6.20 40
4-NO
2
1.35 88
6-Hydroxy- 5.85, 9.15 44
4-Br 3.31 88
8-Hydroxy- 5.66, 8.40 44
1-Hydroxy- --, 1.44 39
2-Methylisoquinolone -1.8 44
5-Methyl-1-phenazone --, 4.9 39
Isoquinoline 5.46, 5.14 44, 19
m-Phenanthroline 3.11
a
19
Phenazine --, 1.23 39
1-Amino- ca. 7.3, 7.29
a
19
2-Hydroxy- 7.5, 2.6 39
2,2'-Dipyridyl 4.23 19
10-Methyl-2-phenazone --, 3.0
2-Hydroxy- 8.79, 4.82 44
6-Aminophenanthridine 6.88 40
7-Hydroxy- 4.38, 8.68 44
9-Aminophenanthridine 7.31 40
9-Methoxy- --, 2.38 44
o-Phenanthroline 4.27
a
, 5.2 19
2-Amino-9-methyl- 5.66
a
19
p-Phenanthroline 3.12
a
19
2,7-Diamino-9-methyl- 6.26
a
19
1,10-Diamino-3,8-Dimethyl- 8.78
a
, 6.31
a
6-Amino- 6.88 40
Phenazine 1.23 19
Phenanthridine --, 4.65 44
1-Amino- 2.6
a
19
6-Hydroxy- 8.43, 5.35 44
2-Amino- 4.75, 3.46
a
19
9-Hydroxy (phenanthridone) <-1.5 44
1,3-Diamino- 5.64
a
19
9-Amino- 7.31, 6.75
a
19
2,3-Diamino- 4.74 19
2,7,9-Triamino- 8.06
a
19
2,7-Diamino- 4.63, 3.9
a
19
Phthalazine 3.47 19
Pteroylglutamic acid 8.26 77
1-Amino- 6.60 19
1-Hydroxy- 11.00, -2 39
Pyridines
Picolimic acid 5.52 4
2-Amino- 6.86 41
5,5-dimethyl-2-thio- 8.71 42
4-Amino- 9.17 41
5,5-Diphenyl-2-thio- 7.69 42
2-Methyl- 5.94
b
45
1-Methyl-5,5-pentamethyl-ene-2-thio-
2-Vinyl- 4.98 45
9.25 42
2-Chloro- 0.49 45
4-Methyl- 7.45 43
2,4,6-Trihydroxy- 4,6, 9.0, 13 39
Imidazole 6.95 43
1-Methyl-4-pyridone 3.33
4-(2',4'-Dihydroxyphenyl)- 6.45 43
2-(N-Methylacetamido)- 2.01 46
Carbobenzoxy-L-histidyl-L-tyrosine ethyl
ester 6.25 43
2-Benzamido- 3.33
2-(N-Methylbenzamido)- 1.44
6-Aminobenz- 6.0 (NH
2
3.0)
3-(N-Methylacetamod)- 3.52 46
Benzimidazole 5.4 43
3-(N-Methylbenzamido)- 3.66 46
4-(N-Methylacetamido)- 4.62 46
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 24
4-(N-Methylbenzamido)- 4.68 46
(CH
3
)
2
CH- 5.83
b
5.72
b
6.02
b
4-Benzamido- 5.32 46
CH
3
CO 3.18
b
3-NO
2
0.81 88
H
2
N- 6.68
b
5.80
b
8.96
b
3-COO
–
4.77 47
CONH
2
47
3.40 3.61
2,3-Me
2
6.60 48
NC-
47
1.45
2,5-Me
2
6.47 48
3,4-Me
2
6.52 48
2,4,6-Me
3
7.48 48
4-OEt 6.67 48
3-Cl 2.84 48
3-CO
2
Et 3.35 48
3-COOH 3.13 88
2-Amyl- 6.00
b
45
2-Hexyl- 5.95
b
45
2-Benzyl- 5.13 45
2-Bromo- 0.71 45
2,4-Dihydroxy 6.50, 13, 1.37 39
1-Methyl-2-pyridone 0.32 39
2-Acetamido- 4.09 46
1-Methylpyrid-2-one acetylimine 7.12 46
3-Acetamido- 4.46 46
3-Benzamido- 3.80 46
1-Methylpyrid-4-one acetylimine
11.03 46
1-Methylpyrid-4-one benzylimine 9.89 46
4-COO
–
4.90 47
2,4-Me
2
6.72 48
2,6-Me
2
6.77 48
3,5-Me
2
6.14 48
2-Me,5-Et 6.51 48
3-F 3.10 48
3-Br 2.84 48
4-CO
2
Et 3.45 48
Pyridine N-oxides (see oxygen acids)
Substituted Pyridines
Pyridine 2- 3- 4-
H- 5.17
b
Cl- 0.72
b
2.84
b
I- 1.82
b
3.25
b
CH
3
CH
2
- 5.97
b
5.70
b
6.02
b
(CH
3
)
3
C- 5.76
b
5.82
b
5.99
b
HO- 0.75 4.86 3.27
11.62 8.72 11.09
SO
3
-47
2.9
CH
3
O- 3.28 4.88 6.62
F- -0.44
b
2.97
b
Br- 0.90
b
2.84
b
CH
3
- 5.97
b
5.68
b
6.02
b
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 25
Ortho-Substituted Pyridines (in 50% ethanol) Pyridazine 2.33 19
Substituent pK ref. 3-Hydroxy- 10.46, -1.8 39
H- 4.38 2 3,6-Dihydroxy- 5,67, -2.2, 13 39
2-C
2
H
5
- 4.93 2 4-Methoxy- 3.70 39
3-Amino- 5.19 19
2-(CH
3
) 4.68 2
4-Hydroxy- 8.68, 1.07 39
2,6-[(CH
3
)
2
CH]
2
3.58 2
3-Methoxy- 2.52 39
2-(CH
3
)
3
C- 4.68 2
3,6-Dimethoxy- 1.61 39
2-C
2
H
5
-6-(CH
3
)
3
C- 4.36 2
2,6-[(CH
3
)
3
C]
2
–
3.58 2
For complex chelating agents, see also ref. 77
2-CH
3
- 5.05 2
b
thermodynamic at 25°.
2-(CH
3
)
2
CH- 4.82 2
2,6-(CH
3
)
2
5.77 2
2,6-[(CH
3
)
3
C]
2
3.58 2
2-CH
3
-6-(CH
3
)
3
C 5.52 2
2-(CH
3
)
2
CH-6-(CH
3
)
3
C- 5.13 2
pK
NH
35° pK
OH
Benzimidazole 6.00 5.58 5.36
2-Methyl 6.96 6.29 6.18 ---
2-Ethyl 6.90 6.27 6.14 --
2-Hydroxymethyl --- 5.40 --- 11.55 ref. 86
1-Methyl-2-hydroxymethyl --- 5.55 --- 11.45
2,4-Dihydroxy-(Uracil) 9.38, 12 39
4,6-Dihydroxy- 5.4 39
2,4,6-Trihydroxy-(Barbituric acid)
Other (ref. 95) 3.9, 12.5 39
Thiazolidine 6.31 2-Methoxy- <1 39
Methyl thiazolidine-4-carboxylate 4.00 4-Methoxy- 2.5 39
Thiazolidine-4-COOH 1.51, 6.21 1-Methyl-2-pyrimidone 2.50 39
3-Methyl-4-pyrimidone 1.84 39
(ref. 96) 4-Amino- 5.71 19
2-Methyl-∆
2
-oxazoline 5.5
2-Amino-4-methyl- 4.15 19
2,4-Diamino- 7.26 19
4-Carbamoyl-2-phenyl-∆
2
-oxazoline 2.9
4-Methyl- 1.98 19
2-Phenyl-∆
2
-oxazoline 4.4
4-Hydroxy- 8.59, 1.85 39
4,5-Dihydroxy- 7.48, 1.99, 11.61 39
Heterocyclics
2,4,5-Trihydroxy-(isoBarbituric acid)
Pyrazines pK ref.
8.11, 11.48 39
Pyrazine 1.1, 0.6 49, 39
4-Hydroxy-5-methoxy- 8.60 1.75
39
2,5-Dimethyl- 2.1 49
2,3,5,6-Tetramethyl- 2.8 49
1-Methyl-4-pyrimidone 1.8 39
2-Methoxy- --, 0.75 39
2-Methyl- 1.5 49
Miscellaneous
2,6-Dimethyl- 2.5 49
4-Hydroxy-2-methylpyridazinium chloride
1.74 44
2-Hydroxy- 8.23, 0.1 39
1-Methyl-2-pyrazine -0.04 39
8-Hydroxy-6-methyl-1,6-naphthyridinium
chloride 4.34 44
2-Amino- 3.14 19
Pyrimidine 1.30 19
2-Hydroxyphenazine 2.6 44
2-Amino- 3.54 19
4-Hydroxypteridine -0.17 44
5-Amino- 2.83 19
3-Methyl-4-pteridone -0.47 44
2-Amino-4,6-dimethyl- 4.85 19
5-Hydroxypyrimidine 1.87, 6.78 44
2,4,6-Triamino- 6.84 19
8-Hydroxy-1,6-Naphthyridine 4.08 44
2-Hydroxy- 9.17, 2.24 39
1-Hydroxyphenazine 1.44 44
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 26
5-Methyl-1-phenazone 4.9 44
10-Methyl-2-phenazone 3.0 44
1-Methyl-4-pteridone 1.25 44
Quinoline 2-- 3 4 5 6 7 8 Ref.
H- 4.85* 4.80 4.69* 2
H
2
N- 7.25* 4.86* 9.08* 5.37* 5.54* 6.56* 3.90* 2
HO- -.36 4.30 2.27 5.20 5.17 5.48 5.13 44
11.74 8.06 11.25 8.54 8.88 8.85 9.89 44
CH
3
5.42 5.14 5.20 4.62 4.92 5.08 4.60 2
5.8 5.6 5.2 5.0 2
F- 2.36* 3.68* 4.00* 4.04* 3.08* 2
Cl- 3.73* 2
HO
2
C 4.96* 4.62* 4.53* 4.81* 4.98* 4.97* 7.20* 2
NO
2
1.03
88
5-Hydroxy-1-methylquioxalinium chloride
5.74 44Quinoline
2,4-Dihydroxy- 5.86, 0.76 39 Riboflavin 9.93 77
4-Methoxy- 6.65 59 Sulphadiazine 6.48 6
1-Methyl-4-quinolone 2.46 39 Sulphapyridine 8.43 6
2,4-Diamino- 9.45 19 2-Aminothiazole 5.39 41
Quinazoline 3.51, 3.2
a
19
1,3,5-Triazine -- 39
2,4-Dihydroxy- 6.5 39
2-Amino- 4.43 19
1,4,6-Triazanaphthalene 2.5 39
6-Amino- 3.2
a
19
4-Hydroxy- 11.05, 0.78 39
2-Hydroxy- 10.69, 1.30 39
5-Amino- 2.62 19
6-Hydroxy- 8.19, 3.12 39
2,3-Diamino- 4.70 19
3-Methiodide 7.26 39
5-Hydroxy- 8.65, 0.9 39
2-Methoxy- 1.31 39
6-Hydroxy- 7.92, 1.40 39
2-Methoxy- 3.17 39
1,5-Naphthyridine 2.91 39
1-Methyl-2-quinolone -0.71 39
4-Hydroxy 10.01, 2.85 39
4-Amino- 9.44, 9.17 19, 41
Sulphaquanidine 11.25 6
8-Quinolinol 5.13, 9.89 6
Sulphathiazole 7.12 6
3-Cl --, 2.46 88, 44
Terramycin 3.10, 7.26, 9.11
77
3-Br 2.61 88
4-Amino- 5.73 19
Tetramethylenediamine 10.7 4
8-Amono- 2.4
a
19
1,4,5-Triazanaphthalene 1.20 39
4-Hydroxy- 9.81, 2.12 39
8-Hydroxy- 8.76, 0.60 39
8-Hydroxy- 8.65, 3.41 39
2,4-Dihydroxy- 9.78, 2.5 39
4-Methoxy- 3.13 39
SPECIAL NITROGEN COMPOUNDS
*Thermodynamic
Hydroxylamines
Hydroxylamine 5.97* 12
Heterocyclics
N-Methyl- 5.96* 12
Quinoxaline 0.8, 0.56 19, 39
O-Methyl- 4.60* 12
2-Amino- 3.96 19
Trimethyl- 3.65* 12
6-Amino- 2.95 19
N-Dimethyl- 5.20* 12
2-Hydroxy- 9.08, -1.37 39
N,O-Dimethyl- 4.75* 12
1-Methiodide 5.74 39
2,3-Dihydroxy- 9.52 39
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 27
Hydrazines (30°) Phenylguanidine 10.88 19
Hydrazine 8.07 13 Benzamidine 11.6 19
Methyl- 7.87 13 N-Phenyl-O-methylisourea 7.3 20
N,N'-Dimethyl- 7.52 13
Tetramethyl- 6.30 13
N,N-Diethyl- 7.71 13 Nitrogen compounds, miscellaneous
Phenyl- 5.21 (15°) 14
Diguanide
--
3.07, 13.25 77
Glycylhydrazide 2.38, 7.69 15
Dithiooxamide (rubeanic acid,
N,N-Dimethyl- 7.21 13
H
2
NCSCSNH
2
) 10.62 77
Trimethyl- 6.56 13
Ethylenediguanide
Ethyl- 7.99 13
1.74, 2.88, 11.34, 11.76 77
N,N'-Diethyl- 7.78 13
Phenyldiguanide 2.16, 10.71 77
Acet- 3.24 15
Isonicotinhydrazide 1.85, 3.54, 10.77
77
Other
S-Methylisothiourea 9.83 20
Hydrazones Hydrazone of:
N-Phenyl-S-methylisothiourea 7.14 20
Benzophenone 3.85 16
p,p'-Dimethoxy- 4.38 16
p-Chloro- 4.38 16
Cinchona Alkaloids (in 80% aqueous methyl
cellosolve)
p-Methoxyacetophenone 4.94 16
p,p'-Dichloro- 3.13 16
Quinine 7.73 2
Phenyl-2-thienyl ketone 3.80 16
Quinidine 7.95 2
Ephedrine 9.14 2
Semicarbazones of:
N-Methylephedrine 8.50 2
Semicarbazide 3.66
Epiquinine 8.44 2
Furfural 1.44 14
Epiquinidine 8.32 2
Benzaldehyde 0.96 14
ψ-Ephedrine 9.22 2
Acetone 1.33 14
N-Methyl-ψ-ephedrine 8.81 2
Acetaldehyde 1.10 14
Pyruvic acid 0.59 14
Acetamide -0.51 4
Urea 0.18 4
Thiourea -0.96 4
Amidoximes
Ox- 3.02 17
Benz- 4.99 17
Thiols
α-Phenylacet- 5.24 17
N-Dimethyl-cysteamine 7.95, 10.7 7
Succin- 3.11, 5.97 17
N-Dipropyl-cysteamine 8.00 10.8 5
o-Tolu- 4.03 17
N-β-Mercaptoethyl-morpholine 6.65, 9.8
p-Tolu- 5.14 17
1-Diethylamino-butan- (4) 10.1 5
Malon- ~4.77 17
Methyl-[β-diethylamino-ethyl]-sulfide 9.8
5
Other
Methyl thioglycolate 7.8 23
Diphenylthiocarbazone 4.5 6
Mercaptoethylamine 8.6, 10.75 23
Phthalimide 8.30 18
N-trimethyl cysteine 8.6 23
Nitrourethane 3.28 18
Glutathione 2.12, 3.59, 8.75, 9.65 23
Acetylguanidine 8.33 19
N-Diethyl-cysteamine 7.8, 10.75 5
Acetamidine 12.52 19
N-Β-Mercaptoethyl-piperidine
O-Methylisourea 9.80 20
7.95, 11.05 5
Dimedone 5.23 18
1-Diethylamino-propan- (3) 8.0, 10.5 5
Nitrourea 4.57 18
1-Diethylamino-hexan- (6) 10.1 5
Guanidine 13.71 19
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 28
p-Nitrobenzenethiol 5.1 58 o-Mercapto-phenylacetic acid
Thioglycolic acid 3.67, 10.31 23 4.28, 7.67 59
Mercaptoethanol 9.5 23 Ethyl mercaptan 10.50 81
Cysteine 1.8, 8.3, 10.8 23 I-Thio-D-sorbitol 9.35 91
Cysteinylcysteine 2-mercaptoethanesulfonate 7.53 (9.1) 81
2.65, 7.27, 9.35, 10.85 23 o-aminothiophenol 6.59 81
Thiophenol 8.20
a
, 7.8, 6.52 59, 81, 82
Β-Mercaptopropionic acid 10.27 81
X= -H -S
–
-SH
Methyl cysteine 6.5 (7.5)
81
X(CH
2
)
2
SH 12.0 13.96 10.75
X(CH
2
)
4
SH 12.4 13.25 11.50 p-Cl-thiophenol 7.50 81
X(CH
2
)
3
SH 13.24 11.14
Mercaptans, RSH
X(CH
2
)
5
SH 13.27 11.82
R
CH
3
CCH
2
- 7.86 32
C
6
H
5
CH
2
- 9.43 82
HOCH
2
CH(OH)CH
2
- 9.51 82
CH
2
=CHCH
2
- 9.96 82
n-C
4
H
9
- 10.66 82
t-C
5
H
11
- 11.21 82
C
2
H
5
OCOCH
2
- 7.95 82
C
2
H
5
OCH
2
CH
2
- 9.38 82
HOCH
2
CH(OH)CH
2
- 9.66 82
n-C
3
H
7
- a10.65 82
t-C
4
H
9
- 11.05 82
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 29
CARBON ACIDS Dicyanomethane 12 2
Acetonitrile c. 25 24
Acetone ~20 24 Benzoylacetone (anol) 8.23 24
Acetylacetone 8.95 24 Dimethylsulfone 14 24
Diacetylacetone 6 24 Nitroethane 8.6 18
Hydrocyanic acid 9.21 25 2-nitropropane 7.74 18
1-nitropropane 9 18 Tricyanomethane strong 24
Saccharin 1.6 18 Trinitromethane strong 24
Tri-methylsulfonyl-methane strong 24 Nitromethane strong 25
Bis-( -Diketones):[(RCO)(R'CO)CH]
2
CHR (in 50% dioxane) (ref. 28)
R R' R" pK pK
CH
3
CH
3
(CH
2
)
5
CH
3
11.33 12.52
CH
3
CH
3
C
6
H
5
11.10 12.49
CH
3
CH
3
2-ClC
6
H
4
11.04 12.73
CH
3
CH
3
2-C
5
H
4
N 9.80 12.46
CH
3
CH
3
2-CH
3
OC
6
H
4
11.47 12.44
CH
3
CH
3
3,4-CH
2
O
2
C
6
H
3
11.39 12.60
CH
3
CH
3
3-C
5
H
4
N 10.29 12.63
CH
3
CH
3
4-CH
3
OC
6
H
4
11.62 12.61
CH
3
CH
3
4-(CH
3
)
2
NC
6
H
4
11.50 12.45
CH
3
CH
3
OCH
2
C
6
H
5
11.54 12.27
CH
3
CH
3
OCH
2
2-C
5
H
4
N 10.95 12.49
CH
3
CH
3
OCH
2
4-(CH
3
)
2
NC
6
H
4
12.13 12.31
CH
3
CH
3
OCH
2
4-CH
3
OC
6
H
4
11.74 12.49
CH
3
OCH
2
COCH
2
COCH
3
9.66
(CH
3
CO)
2
CH(CH
2
)
3
CH
3
12.07
Bis-( -Diketones) (RCO)-(R'CO)CH-Y-CH(COR)(COR') (in 50% dioxane) (ref. 26)
R R' Y pK pK
CH
3
CH
3
9.43 13.54
CH
3
CH
3
(CH
2
)
4
11.99 12.48
CH
3
CH
3
(CH
2
)
10
12.01 12.07
CH
3
CH
3
1,4-(CH
3
)
2
C
6
H
4
11.27 12.15
Bis-( -Diketones) RCOCH
2
CO-Y-COCH
2
COR (in 75% dioxane) (ref. 26)
R Y pK pK
C
6
H
5
(CH
2
)
4
12.47 13.09
C
6
H
5
(CH
2
)
5
12.72 13.46
C
6
H
5
(CH
2
)
6
12.60 13.46
C
6
H
5
(CH
2
)
7
13.1 (est.)
C
6
H
5
(CH
2
)
3
12.58 13.69
CH
3
(CH
2
)
5
12.29 13.00
CH
3
=CH(CH
3
)
2
(CH
2
)
5
12.95 13.60
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 30
CH
3
NO
2
10.29 74
CO
2
Et
O
10.96 74
CH
3
CHClNO
2
7 74
CH
3
COCH
2 NO2
5.1 74
CH(NO
2
)
3
strong 74
CH
3
O
O
7.82 74
CH
3
COCHCl
2
15 74
CH
3
COCHC
2
H
5
CO
2
C
2
H
5
12.7 74
CH
3
COCHCH
3
COCH
3
11 74
CH
3
COCH
2
COC
6
H
5
9.4 74
Dinitromethane 4 2
C
6
H
5
COCH
2
COCF
3
6.82 74
Potassium cyanide 9.21 2
CH
3
COCH
2
CHO 5.92 74
CH(CN)
3
strong 74
CH
3 COCH2 CO2
CH
3
10 74
CH
2
(CO
2
C
2
H
5
)
2
13.3 74
CH
3
SO
2
CH
2
SO
2
CH
3
14 74
CH
3
CO
2
H ~ 24 74
CH
3
SO
2
CH(COCH
3
)
2
4.3 74
OEt
O
O
10.5 74
C
2
H
5
NO
2
8.6 74
C
2
H
5
O
2
CCH
2 NO2
5.82 74
CH
2
(NO
2
)
2
3.57 74
10.1 74
CH
3
COCH
2
Cl c. 16.5 74
CH
3
COCH
2
CO
2
C
2
H
5
10.68 74
CH
3
COCH
2
COCH
3
9 74
CH
3
COCHBrCOCH
3
7 74
5 74
CH
3
COCH
2
COCF
3
4.7 74
C
6
H
5
COCH
2
NC
5
H
5
10.51 74
CH(COCH
3
)
3
5.85 74
CH
3
SO
2
CH
3
c. 23 74
2.0 28
CH(SO
2
CH
3
)
3
strong 74
4.9 28
CH
2
(CN)
2
11.81 74
1.65 28
C
2
H
5
O
2
CCH
2
CN 9 74
3.45 28
CH
3
CO
2
C
2
H
5
~ 24.5 74
3.25 28
CHC
2
H
5
(CO
2
C
2
H
5
)
2
15 74
28
CH
3
CONH
2
~ 25 74
4.1 28
S
O
O
CF
3
6.10 74
7.3 28
9.2 28
2.3 28
CH
3
O
O
CH
2
(CHO)
2
Indicators
Tropeoline OO
Bromocresol green
Thymol blue (1)
Methyl orange
Methyl yellow
Neutral red
Bromophenol blue
Bromothymol blue
Thymol blue (2)
Methyl red (1)
Methyl red (2) 5.0 28
Provided by the ACS, Organic Division
Updated 4/7/2022
Page 31
7.4
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Provided by the ACS, Organic Division
Updated 4/7/2022
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