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
p Ka Data Com p iled by R. W illiam s p age-2

ACIDS
Compound pK Ref. H3PO2 2.0, 2.23* 28

AgOH H2PO4– HPO4_ 7.21* 77

Al(OH)3 3.96 4 H3PO3 12.32* 77
As(OH)3 11.2 28 2.0 28
9.22 28 H2PO3–
H3AsO4 6.58* 77
2.22, 7.0, 13.0 28 H4P2O7 1.52* 77
H2AsO4– 6.98* 77 H3 P2O7– 2.36* 77
HAsO4* 11.53* 77 6.60* 77
As2O3 H2P2O7=
0 4 9.25* 77
H3AsO3 9.22* HP2O7=
H3BO3 9.23* 28 HReO4 -1.25 30

H2B4O7 4.00 34 HSCN 4.00 34

HB4O7 9.00 34 H2SeO3 2.6, 8.3, 2.62* 28

Be(OH)2 3.7 4 HSeO3 8.32 77

HBr -9.00 31 H2SeO4 Strong, 2.0 28

HOBr 8.7 28 HSeO4 2.00 34

HOCl 7.53, 7.46 28, 33 H3SiO3 10.0 34

HClO2 2.0 28 H2SO3 1.9, 7.0, 1.76* 28, 77

HClO3 -1.00 28 H2SO4 -3.0, 1.9 28
HClO4 (70%) -10.00 31 HSO3 7.21* 77
CH3SO3H -0.6 31 HSO4– 1.99* 77
HCN 9.40 34 H2S2O4 1.9 29
H2CO3 6.37, 6.35*, 3.58 34, 32 H2Se 3.89* 77
HCO3 10.33* 11.00* 77
30 HSe–
H2CrO4 -0.98 7.00* 77
6.50* 2, 30 H2S
HCrO4 12.92* 77
3.92 34 HS– HSbO2 11.0 34
HOCN
HZ 3.17*, 0.59* 77 HTe 5.00 34
H2GeO3 8.59, 12.72 34, 78 H2Te 2.64, 11.0 34, 78
8.68, 12.7 28 H2TeO3 2.7, 8.0 28
Ge(OH)4
-10.0 31 Te(OH)6 6.2, 8.8 28
HI
11.0 28 8.95 30
HOI H2VO4–
0.8 28
HIO3
H4IO6– 6.00 34 HVO4= 14.4 30
H5IO6 1.64, 1.55, 8.27 34, 28 H2CrO4 0.74 77
HMnO4 -2.25 30 HOCN 3.73 77
NH3OH* 5.98* HSCN 0.85 77
NH4* 9.24* H3PO2 1.07 77
HN3 4.72* H3PO4 2.12* 77
77
3.29 H2S2O3 0.60*, 1.72* 77
HNO2 77
-1.3 H3AuO3 13.3, 16.0 78
HNO3 28
7.99* H3GaO3 H5IO6 10.32, 11.7 78
N2H5+ 28
7.05 3.29, 6.70, 15.0 78
77
H2N2O2 11.0 H4V6O17 (see above!)
34 78
H2N2O2– 12.1 H2NSO3H 1.96
15.7 34 80
1.0
H2OsO5 34
H2O none
H3O+ -1.7 none * Indicates a thermodynamic value.
Pb(OH)2 6.48 (10.92) 4 (78)
PHOSPHATES AND PHOSPHONATES CF3- 1.16, 3.93 57
CCl3- 1.63, 4.81 57

Phosphates N H 3+CH2- 2.35, 5.9 57

Compound pK Ref. (–OOCCH 2)2N H +CH2– --, 5.57 57

Phosphate 1.97, 6.82, 12.5 55 CHCl2- 1.14, 5.61 57
Glyceric acid 2-phosphate 3.6, 7.1 53 CH2CI- 1.40, 6.30 57
Enolpyruvic acid 3.5, 6.4 53 57
CH2Br- 1.14, 6.52
Methyl- 1.54, 6.31 55 57
Ethyl- 1.60, 6.62 55 ( NH
–OOCCH 22 +(CH2)2- --, 6.54
n-Propyl- 1.88,6.67 55 CH2I- 1.30, 6.72 57
n-Butyl- 1.80, 6.84 55 N H 3+CH2CH2- 2.45, 7.00 57
Dimethyl- 1.29 55 C6H 5CH=CH- 2.00, 7.1 57
Di-n-propyl 1.59 55 HOCH2- 1.91, 7.15 57
Di-n-butyl- 1.72 55 2.1, ---, 57
C6H 5N H 2+(CH2)3-
Glucose-3- 0.84, 5.67 Glucose-4- 0.84, 56 7.17 57
C6H 5NH(CH2)3Br(CH2)2-
5.67 α-glycero- 1.40, 6.44 β-glycero- 56 2.25, 7.3 57
1.37, 6.34 54 CH3(CH2)5CH(COO–)- --, 7.5 57
54
3-phosphoglyceric acid 1.42, 3.42 54 C6H 5CH2- 2.3, 7.55 57
2-phosphoglyceric acid 1.42, 3.55, 7.1 N H 3+(CH2)4)- 2.55, 7.55 57

peroxymonophosphoric acid 4.05 69 N H 3+(CH2)5N 2.6, 7.6 57

diphosphoglyceric acid 7.40, 7.99 54 --, 8.00 57
glyceraldehyde- 2.10, 6.75 dioxyacetone- 54 H 3+(CH2)10-
--, 8.25 57
1.77,6.45 54 –OOC(CH2)10-
hexose di- 1.52, 6.31 54 (CH3)3SiCH2- 3.22, 8.70 57
fructose-6- 0.97, 6.11 54 C6H 5CH2- 3.3, 8.4 57
glucose-6- 0.94, 6.11 54 (C6H 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-RC6H 3PO3H 2

ADP 2 strong, 6.6 54 X R
ATP 3 strong, 6.6 54 Cl 4-O2N 1.12, 6.14 57
pyrophosphoric acid 0.9, 2.0, 6.6, 9.4 54 Br 5-O2N (a), 6.14 57
phosphopyruvic acid 3.5, 6.38 creatine phosphate 54 Cl 5-Cl (a), 6.63 57
2.7, 4.5 arginine phosphate 2.8, 4.5, 9.6, 11.2 54 Cl 1.63, 6.98 57
H
arginine 2.02, 9.0, 12.5 54 Br 1.64, 7.00 57
H
amino phosphate (-0.9), 2.8, 8.2 trimetaphosphate 54 Br 1.81, 7.15 57
5-CH3
2.05 54 Cl --, 7.33 57
4-NH2
77 CH3O 1.53, 6.96 57
4-O2N
CH3O H 2.16, 7.77 57
Phosphonates
H 2O3P(CH2)4PO3H 2 <2, 2.75, 7.54, 8.38 57 CH3O 4-O2N --, 8.22 57
H 2O3P(CH2)3PO3H 2 <2, 2.65, 7.34, 8.35 57 HO 4-O2N 1.22, 5.39 57
H 2O3PCH2CH(CH3)PO3H 2 <2, 2.6, 7.00, 9.27 57 O2N H 1.45, 6.74 57
H 2O3PCH2PO3H 2 <2, 2.57, 6.87, 10.33 57 F H 1.64, 6.80 57
I H 1.74, 7.06 57
Methyl- 2.35 57
N H 2H --, 7.29 57
Ethyl- 2.43 57
n-propyl- 2.45 57 CH3H 2.10, 7.68 57

isopropyl- 2.55, 7.75 57 C6H 5 H (a), 8.13 57

n-butyl- 2.59, 8.19 57 isobutyl- 2.70, 8.43 57 HOOC H 1.71, 9.17 57

s-butyl- 2.74, 8.48 57 **These values were obtained in 50% ethanol.

t-butyl- 2.79, 8.88 57 (a) The compounds were not sufficiently soluble.
neopentyl- 2.84, 8.65 57 For graphical plots of a large number of substituted phosphorus compounds see
1,1 Dimethylpropyl- 2.88, 8.96 57 83.
n-hexyl- 2.6, 7.9 57 triphosphate
n-dodecyl- --, 8.25 57 8.90, 6.26, 2.30 77 tetrametaphosphate 2.74 77
CH3(CH2)5CH(COOH)- 1, -- 57
fluorophosphate 0.55, 4.8 56 Acetic acids, substituted
Phosphonates (Ref. 2) H- 4.76* 20
X -H -H -N H3+ -N H3+ O2N- 1.68* 20
X(CH2)PO3H 2 2.35 7.1 1.85 5.35 (CH 3)3N+(CH 1.83* 20
X(CH2)2PO3H 2 2.45 7.85 2.45 7.00 1.95* 20
3)2NH+CH
X(CH2)4PO3H 2 2.55 7.55
3NH2+-
2.16* 20
7.65
X(CH2)5PO3 H2 2.6 2.31* 20
X(CH2)6PO2H 2 2.6 7.9 NH3+- 2.36* 20
8.00
X(CH2)10PO2H 2 CH 3SO2- 2.43* 20
Phosphines in acetonitrile, see ref. 89. NC-
C6H5SO2- 2.44 20
CARBOXYLIC ACIDS HO2C 2.83* 20
Aliphatic C6H5SO- 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 Cl2- 1.29 20
Betaine 1.84 6 F2Br3- 1.24 20
Citric 3.09, 4.75, 5.41 6 Cl3- 0.66 20
Crotonic 4.69 6 F3- 0.65 20
Dihydroxyfumaric 1.14 6 HONC4 0.23 (-0.26) (2) 20
Dethylenediamine- 2.00, 2.67 6 F3C- 3.01 20
tetraacetic 6.16, 10.26 3.07* 20
N3-
Formic 3.77* 2 3.03 20
I-
Fumaric 3.03, 4.54 6 3.12 20
6 C6H5O-
Glyceric 3.55 Glycollic 3.82 3.12 20
6
Glyoxylic 3.32 6 C2H5O2C- 3.35 20
Homogentistic 4.40 6 C6H5S- 3.52* 20
α-keto-β-methyl valeric 2.3 6 CH 3O- 3.53 20
Lactic 3.86 6 NCS- 3.58 20
Maleic 1.93, 6.58 6 CH 3CO- 3.58* 20
Malic 3.40, 5.2 6 C2H5O- 3.60 20
Oxaloacetic (trans-enol) 2.56 6
n-C3H7O 3.65 20
 +(cis-enol) 2.15, 4.06 n-C46H9O 3.66 20
Protocatechuic 4.48 sec.-C
6 4H9O- 3.67 20
Pyruvic 2.50 HS- 6 3.67* 20
Tartaric + 2.99, 4.40 i-C3H6 7O- 3.69* 20
+ or - 2.89, 4.40 CH 36S- 3.72* 20
meso 3.22, 4.85 i-C3H6 7S- 3.72* 20
Vinylacetic 4.42 C6H65CH 2S- 3.73* 20
C2H5S- 3.74* 20
n-C3H7S- 3.77* 20
n-C4H9S- 3.81* 20
HO- 3.83* 20
– 4.05 20
O3S-
(C6H5)3CS- 4.30* 20
C6H5- 4.31* 20
CH 2-CH- 4.35* 20
* Indicates thermodynamic values.

Compound pK ref. Compound pK ref.

trans-CH 3-CH=CHCO2H 4.69* 20 H-CH 2CH 2CO2H 4.88* 2
cis-CH3-CH=CHCO2H 4.44* 2 H-CH=CHCO2H 4.25* 2
C6H5-CH 2CH 2CO2H 4.66* 2 C6H5CH 2CH 2CO2H 4.66* 2
trans-C6H5-CH=CHCO2H 4.44* 2 C6H5CH=CHCO2H** 4.44* 2
m-CH 3OC6H4CH 2CH 2CO2H 4.65* C6H5CH 2CH 2CO2H 4.66* 2
2 C6H5CH=CHCO2H** 4.44 2
m-CH 3OC6H4CH=CHCO2H 4.38* 2 m-ClC6H4CH=CHCO2H** 4.29* 2
m-ClC6H4CH 2CH 2CO2H 4.58* 2

Unsaturated acids, Cis- and Trans-

Cis-Acid Trans-Acid

H R R1 R2

Unsaturated acids (25°)

R1 CO2H H CO2H
R1 R2 cis-acid trans-acid Ref. C C

H- H- 4.25* 4.25* 2
CH 3- H- 4.44* 4.69* 2
Cl- H- 3.32 3.65 2
C6H5- H- 3.88* 4.44* 2
ClC6H4 H- 3.91 4.41 2
6-BrC6H4 H- 4.02 4.41 2
CH 3- CH 3- 4.30 5.02 2
C6H5- H- 5.26*** 5.58*** 2
2,4,6-(CH 3)3C6H2- H- 6.12*** 5.70*** 2
C6H5- 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-
Acetylenedicarboxylic 1.73, 4.40 2 dicarboxylic acid 2.34*, 8.31* 2

∆1-tetrahydrophthalic 3.01, 5.34 2 1,2-trans-cyclopropanedicarboxylic

Bromomaleic 1.45, 4.62 2 3.65*, 5.13* 2
Bromofumaric 1.46, 3.57 2 trans-caronic 3.82*, 5.32* 2
Chlorofumaric 1.78, 3.81 2 1,2-cis-cyclopropane-dicarboxylic
Fumaric 3.02, 4.38 2 3.33*, 6.47* 2
Mesaconic (Dimethylfumaric acid)
3.09, 4.75 2 **trans
Phthalic 2.95, 5.41 2 ***in 40% acetone
Itaconic (1-Propene-2-3-dicarboxylic acid) *thermodynamic
3.85, 5.45 2
Chloromaleic 1.72, 3.86 2
2
Aliphatic

Alicyclic Dicarboxylic acids

Compound pK Ref Compound pK Ref
1,2-trans-Cyclopropane- cis-Ethyleneoxidedicarboxylic 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- Br- 6.08 2 substituted

Lysergic acid, etc.
H- 6.75 2 ergometrine 6.8, -- 2
C2H5O2C- 6.31 2 Dihydroergometrine 7.4, -- 2 NC- 5.90 2 β-dihydrolysergol 8.2, -- 2
Lysergic acid 7.8, 3.3 2 C6H5O- 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)2CH- 4.35*

α-dihydrolysergol 8.3, -- 2 6-methylergoline 8.85, -- 2 (CH 3)3N+- 1.37 3.45 3.43

NC- 3.60* 3.55*
isolysergic acid 8.4, 3.4 2 γ-dihydrolysergic 8.6, 3.6 2 HO2C* 2.95* 3.54 3.51
F3C- 3.79
HO- 2.98* 4.08* 4.58*
I- 2.85* 3.86*
Cl(CH 3)3Si- 2.94* 3.83* 3.99*
C2H5Oi- 4.24* 4.27*
Hydroxycyclohexanecarboxylic acids 4.21* 4.17* 4.45*
Cyclohexanecarboxylic 4.90 2 cis-1,2 C3H7On-
4.24* 4.15* 4.68*
4.80 2 cis-1,3 4.60 2 cis-1,4 C5H11OC6H5CH
4.55*
3CH 2-
4.84 2 trans-1,2 4.68 2 trans- 3.46*
1,3 4.82 2 trans-1,4 4.68 2 3.77 4.35*
(CH 3)3C- 3.46 4.28 4.40*
Aromatic –HO3P- 3.78 4.03 3.95
benzene-CO3H 4.20* 2 – 4.15 4.11
O3S-
Anthracene-1-COOH 3.69 2 H2N- 4.98 4.79 4.92
Anthracene-9-COOH 3.65 2 naphthalene-2-COOH (CH 3)2N- 8.42 5.10 5.03
4.17 2 Naphthalene-1-COOH 3.69 2 –HO3As- 4.22
–O2C-
5.41** 4.60 4.82

Substituted benzoic acids (ref. 2) CH 3NH- 5.3 5.10 5.04

 *thermodynamic COOH
for complex chelating agents, see also ref. 84.
Benzoic acid o m p see also page 9a for more carboxylic acids.

H- 4.20* 4.21* Ortho-substituted benzoic acids

O2N- 2.17* 3.45* 3.44 Benzoic acid pK Ref.
CH 3CO- 2-CH 3- 3.91** 2
3.46 2
CH 3SO2- 3.64* 3.52* 2-t-C4H9-
3.21 2
CH 3S-2,6-(CH 3)2HS- 2,3,4,6-(CH 3)4- 4.00 2
Br- 2.85* 3.81* 4.00* 2,3,5,6-(CH 3)4- 3.52 2
F- 3.27* 3.87* 4.14* 2-C2H5- 3.77 2
CH 3O- 4.09* 4.09* 4.47* 2-C6H5- 3.46** 2
n-C3H7O- 4.24* 4.20* 4.46* 2,4,6-(CH 3)3- 3.43 2
n-C4H9O- 4.25* 4.53* 2,3,4,5-(CH 3)4- 4.22 2
Benzene Polycarboxylic acids Ref. 2
pKIV pKV pKVI
Acid Position of carboxyl pKI pKII pKIII

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*
8
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-carboxyethyliminodiacetic acid 2.30, 6.60
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 Dimethylaminoacetic 2.08, 9.80 N-ethylaminoacetic
2.00, 2.25, 5.57, 10.76 2.30, 10.10
α,β-dimercaptosuccinic 2.40, 3.46, 9.44, 11.82 Gluconic* 3.86
Ethylenediamine-N,N-diacetic 5.58, 11.05 β-hydroxybutyric 4.39
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
PHENOLS
Compound pK Ref. Compound pK Ref.

Chromotropic acid 5.36, 15.6 6 Resorcinol --, 9.15 (30o) 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 4,5- 10.4 5.28 51 hydrochloride 9.99, 4.86 51

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* O2N- 7.23* 8.35* 7.14*

(CH3)3N+- 7.42 8 8 OCH- 6.79 8.00 7.66

CH3SO2- 9.33 7.83 NC- 8.61**7.95

CH3CO- 9.19 8.05 CH3O2C- 8.47*

C2H5O2C- 8.50* n-C4H9O2C- 8.47*

C3H5CH2O2C- 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* CH3S- 9.53 9.53

HO- 9.48 9.44 9.96 HOCH2- 9.92* 9.83* 9.82*

CH3- 10.28*10.08 10.19* C2H5- 10.2 9.9 10.0

CH3O- 9.93 9.65 10.20H2N- 9.71 9.87 10.30

-O2C- 9.94* 9.39*-O3S- 9.29 9.03

--O3P- 10.2 9.9 --O3As 8.37

C6H5- 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
ALCOHOLS and other OXYGEN ACIDS

Alcohols

Compound pK Ref. Compound pK Ref.

Choline 13.9 6 C3F7• CH(C2F5)• OH 10.48 65
Chloral hydrate 9.66, 11.0 61 (C3F7)2CH• OH 10.52 65
Trifluoroethanol 12.5 62 Carbonium ions
CF3CH2OH 11.4, 12.43 63
CF3CH(OH)CH3 11.8 63 Triphenylmethanols in H2SO4 HC1O4 HNO3 ref
CF3CH2(CH3)3OH 12.43 10 4,4,4-Trimethoxy .82. .82 .80 66
C3F7CH2OH 11.4** 63 4,4’-Dimethoxy -1.24 -1.14 -1.11 66
(C3F7)2CHOH 10.6** 63 4-Methoxy -3.40 -3.59 -3.41 66
HCCCH2OH 13.55 64 4-Methyl -5.41 -5.67 66
C(CH2OH))4 14.1 64 4-Trideuteriomethyl- 5.43 5.67 66
HOCH2CHOHCH2OH 4.4 64 3,3’,3”-Trimethyl- 6.35 -5.95 66
HOCH2CH2OH 14.77 64 Unsubstituted triphenyl-
CH3CCH2OH 14.82 64 methanol- 6.63 -6.89 6.60 66
CH3OH 15.54 64 4,4;,4;-Trichloro- 7.74- 8.01 66
CH2=CHCH2OH 15.52 64 4-Nitro- 9.15- 9.76 66
H2O 15.74 64 CCl3CH2OH 11.8***
CH3CH2OH 16 64 CF3CH2OH 11.3***
Substituent effects for ionization of RCH2OH
R
CCl-3 12.24,11.80 64,65
CF3- 12.37 64
CHF2CH2- 12.74 64 Hydroxamic acids
CHCl2- 12.89 64 Furo- 8.45 72
CHEC- 13.55 64 Glycine 7.40 72
H2Cl- 14.31 64 Hippuro- 8.80 72
CH3CCH2- 14.8 64 isoNicotin 7.85 72
HOCH2 15.1 64 p-Methylbenz- 8.90 72
H- 15.5 64 Nicotin- 8.30 72
CH2=CH- 15.5 64 Nicotin-methiodide 6.46 72
CH3-(extrap) (15.9) 64 m-Nitrobenz- 8.07 72
CF3C(CH3)2OH 11.6 64 Picolin 8.50 72
HOCH2CF2CH2OH 11 64 Pyrimidine-2-carbox- 7.88 72
Primary alcohols=R• CH2• OH and Salicyl- 7.43 72
Secondary alcohols in 50% alcohol Tropo- 9.09 72
C2F5 11.35 65
C4F9 11.35 65
C5F11 11.37 65
C7F15 11.35 65 Other oxygen acids
CHF2 12.00 65 Trimethylamine-n-oxide 4.6 18
CF2Cl 11.63 65 Dimethylglyoxime 12.84 77
CHF2CF2 11.34 65 (50% dioxane)
CHF2 • (CF2)2 11.35 65 O-methyl ether 12.92 77
CF3 • CH2 12.7 65 Tropolone 12a 77
a
CF3 • (CH2)2 12.9 65 α-Bromotropolone 6.95 77
CF3 • CHMe • OH 11.28 65 Acetald hydrate 13.48 91
C3F7 • CHMe • OH 11.38 65 Formald hydrate 13.29 91
C3F7CHEt • OH 11.37 65
C3F7CHPr • OH 11.37 65
a
C3F7 • CH(CF3) • OH 10.46 65 50% dioxane
***50 aquaeous ethanol