Idea Transcript
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APPE N DIX G
Acid Dissociation Constants Ionic strength () ⴝ 0
Name
Structure*
Acetic acid (ethanoic acid)
CH3CO2H
pKa†
0.1 M§
Ka‡
pKa†
4.756
1.75 105
4.56
2.344 (CO2H) 9.868 (NH3)
4.53 103 1.36 1010
2.33 9.71
4.601
2.51 105
4.64
3.232
5.86 104
3.01
2.08 (CO2H) 4.96 (NH3)
8.3 103 1.10 105
2.01 4.78
NH3
Alanine
CHCH3 CO2H NH3
Aminobenzene (aniline) 4-Aminobenzenesulfonic acid (sulfanilic acid)
NH3
O S 3
NH3
2-Aminobenzoic acid (anthranilic acid)
CO2H
2-Aminoethanethiol (2-mercaptoethylamine)
HSCH2CH2NH3
2-Aminoethanol (ethanolamine)
HOCH2CH2NH3
—— —— 9.498
3.18 1010
9.52
4.70 (NH3) (20°) 9.97 (OH) (20°)
2.0 105 1.05 1010
4.74 9.87
9.245
5.69 1010
9.26
1.823 (CO2H) 8.991 (NH3) —— (NH2)
1.50 102 1.02 109 ——
2.03 9.00 (12.1)
2.24 6.96 (11.50)
5.8 103 1.10 107 3.2 1012
2.15 6.65 (11.18)
9.29
5.1 1010
9.14
OH
2-Aminophenol NH3
Ammonia
NH4 NH3
Arginine
NH2
CHCH2CH2CH2NHC NH2
CO2H O As
Arsenic acid (hydrogen arsenate)
HO
Arsenious acid (hydrogen arsenite)
As(OH)3
OH
NH3
Asparagine
OH
8.21 (SH) 10.73 (NH3)
O
CHCH2CNH2 CO2H
—— ——
—— ——
2.16 (CO2H) 8.73 (NH3)
*Each acid is written in its protonated form. The acidic protons are indicated in bold type. †
pKa values refer to 25⬚C unless otherwise indicated. Values in parentheses are considered to be less reliable. Data are from A. E. Martell, R. M. Smith, and R. J. Motekaitis, NIST Database 46 (Gaithersburg, MD: National Institute of Standards and Technology, 2001). The accurate way to calculate Kb for the conjugate base is pKb 13.995 pKa and Kb 10pKb.
‡
See marginal note on page 166 for distinction between pKa at 0 and at 0.1 M.
§
(Continued)
APPENDIX G Acid Dissociation Constants
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Ionic strength () ⴝ 0 Name
Structure NH3
Aspartic acid
pKa
CHCH2CO2H CO2H
Aziridine (dimethyleneimine)
Benzene-1,2,3-tricarboxylic acid (hemimellitic acid)
NH2 CO2H CO2H
0.1 M
Ka
pKa
1.02 102 1.26 104 9.95 1011
1.95 3.71 9.96
8.04
9.1 109
——
2.86 4.30 6.28
1.38 103 5.0 105 5.2 107
2.67 3.91 5.50
6.28 105
4.01
1.990 (-CO2H) 3.900 ( -CO2H) 10.002 (NH3)
CO2H
Benzoic acid
CO2H
4.202
Benzylamine
CH2NH3
9.35
4.5 1010
9.40
—— 4.34
—— 4.6 105
(1.3) 4.41
5.79 1010 1.82 1013 1.58 1014
8.98 —— ——
1.25 103
2.71
2,2-Bipyridine
N N H H
9.237 (12.74) (20°) (13.80) (20°)
Boric acid (hydrogen borate)
B(OH)3
Bromoacetic acid
BrCH2CO2H
Butane-2,3-dione dioxime (dimethylglyoxime) Butanoic acid
cis-Butenedioic acid (maleic acid)
trans-Butenedioic acid (fumaric acid) Butylamine
NOH
HON CH3
CH3
CH3CH2CH2CO2H CO2H CO2H CO2H HO2C
CH3CH2CH2CH2NH3 O
2.902
10.66 (12.0)
2.2 1011 1 1012
10.45 (11.9)
4.818
1.52 105
4.62
1.92 6.27
1.20 102 5.37 107
1.75 5.84
3.02 4.48
9.5 104 3.3 105
2.84 4.09
10.640
2.29 1011
10.66
6.351 10.329
4.46 107 4.69 1011
6.13 9.91
Carbonic acid* (hydrogen carbonate)
HO
Chloroacetic acid
ClCH2CO2H
2.865
1.36 103
2.69
3-Chloropropanoic acid
ClCH2CH2CO2H
4.11
7.8 105
3.92
Chlorous acid (hydrogen chlorite)
HOCl£O
1.96
1.10 102
——
C
OH
*The concentration of “carbonic acid” is considered to be the sum [H2CO3] [CO2(aq)]. See Box 6-4.
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APPENDIX G Acid Dissociation Constants
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Ionic strength () ⴝ 0 Name
Structure
pKa
0.1 M
Ka
pKa
O
Chromic acid (hydrogen chromate)
Citric acid (2-hydroxypropane-1,2,3tricarboxylic acid)
Cr
HO
OH
O CO2H HO2CCH2CCH2CO2H
(0.2) (20°) 6.51
1.6 3.1 107
3.128 4.761 6.396
7.44 104 1.73 105 4.02 107
(0.6) (20 C) 6.05
2.90 4.35 5.70
OH
Cyanoacetic acid
NCCH2CO2H
2.472
3.37 103
Cyclohexylamine
NH3
10.567
2.71 1011
10.62
(1.7) (CO2H) 8.36 (SH) 10.74 (NH3)
2 102 4.4 109 1.82 1011
(1.90) 8.18 10.30
Cysteine
NH3 CHCH2SH
——
CO2H
Dichloroacetic acid
Cl2CHCO2H
(1.1)
8 102
(0.9)
Diethylamine
(CH3CH2)2NH2
11.00
1.0 1011
11.04
9.45 ——
3.5 1010 ——
9.26 (13.3)
—— ——
—— ——
9.30 11.06
3.036 4.366
9.20 104 4.31 105
2.82 3.97
—— ——
—— ——
8.63 10.65
10.774
1.68 1011
10.81
4.114
7.69 105
3.92
OH
1,2-Dihydroxybenzene (catechol)
OH OH
1,3-Dihydroxybenzene (resorcinol)
OH OH
D-2,3-Dihydroxybutanedioic
acid (D-tartaric acid)
2,3-Dimercaptopropanol
HO2CCHCHCO2H OH HOCH2CHCH2SH SH
Dimethylamine
(CH3)2NH2 NO2
2,4-Dinitrophenol
O2N
OH
Ethane-1,2-dithiol
HSCH2CH2SH
—— ——
—— ——
Ethylamine
CH3CH2NH3
10.673
2.12 1011
10.69
Ethylenediamine (1,2-diaminoethane)
H3NCH2CH2NH3
6.848 9.928
1.42 107 1.18 1010
7.11 9.92
8.85 (30 C) 10.43 (30 C)
(Continued) APPENDIX G Acid Dissociation Constants
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Ionic strength () ⴝ 0 Name
Structure
pKa
Ethylenedinitrilotetraacetic acid (EDTA)
(HO2CCH2)2NHCH2CH2NH(CH2CO2H)2
—— (CO2H) —— (CO2H) —— (CO2H) —— (CO2H) 6.273 (NH) 10.948 (NH)
Formic acid (methanoic acid)
HCO2H
NH3
Glutamic acid
CHCH2CH2CO2H CO2H
NH3
Glutamine
0.1 M
Ka
pKa
—— —— —— —— 5.3 107 1.13 1011
(0.0) (CO2H) ( 1 M) (1.5) (CO2H) 2.00 (CO2H) 2.69 (CO2H) 6.13 (NH) 10.37 (NH)
3.744
1.80 104
3.57
2.160 (-CO2H) 4.30 ( -CO2H) 9.96 (NH3)
6.92 103 5.0 105 1.10 1010
2.16 4.15 9.58
O
CHCH2CH2CNH2 CO2H
—— ——
—— ——
2.19 (CO2H) 9.00 (NH3)
NH3
Glycine (aminoacetic acid)
Guanidine 1,6-Hexanedioic acid (adipic acid)
Hexane-2,4-dione
CH2
2.350 (CO2H) 9.778 (NH3)
CO2H NH 2
H2N
C
NH2
HO2CCH2CH2CH2CH2CO2H O
O
CH3CCH2CCH2CH3 NH3
Histidine
NH
CHCH2
N H
CO2H
Hydrazine
H3N NH3
Hydrazoic acid (hydrogen azide)
HN
Hydrogen cyanate
HOCΩN
N
N
—— 4.424 5.420
9.38
(1.6) (CO2H) 5.97 (NH) 9.28 (NH3)
4.47 103 1.67 1010
2.33 9.57
(13.5) ( 1 M)
—— 3.77 105 3.80 106 4.2 1010
3 102 1.07 106 5.2 1010
4.26 5.04 9.11 (20 C)
(1.7) 6.05 9.10
0.99 7.98
1.0 101 1.05 108
4.65
2.2 105
4.45
3.48
3.3 104
——
10
(0.21) ( 0.5 M) 8.07
Hydrogen cyanide
HCΩN
9.21
6.2 10
9.04
Hydrogen fluoride
HF
3.17
6.8 104
2.94
Hydrogen peroxide
HOOH
11.65
2.2 1012
——
Hydrogen sulfide
H2S
Hydrogen thiocyanate
HSCΩN
Hydroxyacetic acid (glycolic acid)
HOCH2CO2H
7.02 14.0* (1.1) (20°C) 3.832
8
9.5 10 1.0 1014*
6.82 ——
1.3 101
——
4
1.48 10
3.62
*D. J. Phillips and S. L. Phillips. “High Temperature Dissociation Constants of HS and the Standard Thermodynamic Values for S2,” J. Chem. Eng. Data 2000, 45, 981.
AP14
APPENDIX G Acid Dissociation Constants
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Ionic strength () ⴝ 0 Name
Structure
Hydroxybenzene (phenol)
9.997
OH
CO2H
2-Hydroxybenzoic acid (salicylic acid)
L-Hydroxybutanedioic
pKa
OH OH
acid
(malic acid) Hydroxylamine
8-Hydroxyquinoline (oxine)
2.972 (CO2H) (13.7) (OH)
N H
HO
pKa
1.01 1010
9.78
1.07 103 2 1014
2.80 (13.4)
3.24 4.68
5.96 (NH) (13.74) (OH)
1.10 106 1.8 1014
5.96 ——
4.94 (NH) 9.82 (OH)
1.15 105 1.51 1010
4.97 9.65
HONH3
Ka
3.48 104 8.00 106
3.459 5.097
HO2CCH2CHCO2H
0.1 M
Hypobromous acid (hydrogen hypobromite)
HOBr
8.63
2.3 109
——
Hypochlorous acid (hydrogen hypochlorite)
HOCl
7.53
3.0 108
——
Hypoiodous acid (hydrogen hypoiodite)
HOI
10.64
2.3 1011
——
(1.3)
5 102
Hypophosphorous acid (hydrogen hypophosphite) Imidazole (1,3-diazole)
Iminodiacetic acid
O
(1.1)
H2POH NH
6.993 (14.5)
N H
(1.85) (CO2H) 2.84 (CO2H) 9.79 (NH2 )
H2N(CH2CO2H)2 O
0.77
Iodic acid (hydrogen iodate)
HOI
Iodoacetic acid
ICH2CO2H
1.02 107 3 1015
7.00 ——
1.41 102 1.45 103 1.62 1010
(1.77) 2.62 9.34
0.17
——
O
3.175
6.68 104
2.98
2.318 (CO2H) 9.758 (NH3)
4.81 103 1.75 1010
2.26 9.60
2.328 (CO2H) 9.744 (NH3)
4.70 103 1.80 1010
2.32 9.58
(1.77) (CO2H) 9.07 (-NH3) 10.82 ( -NH3)
1.7 102 8.5 1010 1.51 1011
2.15 9.15 10.66
NH3
Isoleucine
CHCH(CH3)CH2CH3 CO2H NH3
Leucine
CHCH2CH(CH3)2 CO2H NH 3
Lysine
CHCH2CH2CH2CH2NH3 CO2H
(Continued) APPENDIX G Acid Dissociation Constants
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Ionic strength () ⴝ 0 Name
Structure
pKa
Malonic acid (propanedioic acid)
HO2CCH2CO2H
Mercaptoacetic acid (thioglycolic acid)
HSCH2CO2H
2-Mercaptoethanol
HSCH2CH2OH
2.847 5.696 3.64 (CO2H) 10.61 (SH) 9.72
0.1 M
Ka
pKa
1.42 103 2.01 106
2.65 5.27
2.3 104 2.5 1011
3.48 10.11
1.9 1010
9.40
NH3
Methionine
CHCH2CH2SCH3 CO2H OCH3
2-Methoxyaniline (o-anisidine)
—— ——
2.18 (CO2H) 9.08 (NH3)
4.526
2.98 105
5.357
4.40 106
5.33
10.632
2.33 1011
10.65
4.447
3.57 105
——
5.080
8.32 106
5.09
——
NH3
4-Methoxyaniline ( p-anisidine)
CH3O
Methylamine
CH3NH3
NH3
CH3
2-Methylaniline (o-toluidine) 4-Methylaniline ( p-toluidine)
—— ——
NH3
CH3
NH3 CH3
2-Methylphenol (o-cresol)
10.31
4.9 1011
10.09
10.269
5.5 1011
10.04
OH
4-Methylphenol ( p-cresol)
CH3
Morpholine (perhydro-1,4-oxazine)
O
OH
NH2
8.492
3.22 109
——
3.67
2.1 104
——
4.16
6.9 105
——
9.416
3.84 1010
9.14
9.573
2.67 1010
9.31
—— 0.010 1.15 103 4.63 1011
(1.0) 1.81 2.52 9.46
CO2H
1-Naphthoic acid
CO2H
2-Naphthoic acid
OH
1-Naphthol
OH
2-Naphthol
Nitrilotriacetic acid
AP16
HN(CH2CO2H)3
—— (CO2H) 2.0 (CO2H) (25°) 2.940 (CO2H) (20°) 10.334 (NH) (20°)
APPENDIX G Acid Dissociation Constants
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Ionic strength () ⴝ 0 Name
Structure
⫽ 0.1 M
pKa
Ka
2.185
6.53 ⫻ 10⫺3
——
3.449
3.56 ⫻ 10⫺4
3.28
3.442
3.61 ⫻ 10⫺4
3.28
8.57
2.7 ⫻ 10⫺9
——
7.230
5.89 ⫻ 10⫺8
7.04
8.37
4.3 ⫻ 10⫺9
8.16
7.149
7.10 ⫻ 10⫺8
6.96
pKa
NO2
2-Nitrobenzoic acid
CO2H NO2
3-Nitrobenzoic acid CO2H
4-Nitrobenzoic acid
O2N
CO2H
Nitroethane
CH3CH2NO2 NO2
2-Nitrophenol OH NO2
3-Nitrophenol OH
4-Nitrophenol
O2N
N-Nitrosophenylhydroxylamine (cupferron)
OH NO
N
OH
——
——
4.16
Nitrous acid
HON£O
3.15
7.1 ⫻ 10⫺4
——
Oxalic acid (ethanedioic acid)
HO2CCO2H
1.250 4.266
5.62 ⫻ 10⫺2 5.42 ⫻ 10⫺5
(1.2) 3.80
3.46
3.5 ⫻ 10⫺4
3.05
2.56 4.37
2.8 ⫻ 10⫺3 4.3 ⫻ 10⫺5
2.26 3.90
Oxoacetic acid (glyoxylic acid)
Oxobutanedioic acid (oxaloacetic acid) 2-Oxopentanedioic (␣-ketoglutaric acid) 2-Oxopropanoic acid (pyruvic acid)
O HCCO2H O HO2CCH2CCO2H O HO2CCH2CH2CCO2H O
—— ——
—— ——
(1.9) ( ⫽ 0.5 M) 4.44 ( ⫽ 0.5 M)
2.48
3.3 ⫻ 10⫺3
2.26
CH3CCO2H
1,5-Pentanedioic acid (glutaric acid)
HO2CCH2CH2CH2CO2H
4.345 5.422
4.52 ⫻ 10⫺5 3.78 ⫻ 10⫺6
4.19 5.06
Pentanoic acid (valeric acid)
CH3CH2CH2CH2CO2H
4.843
1.44 ⫻ 10⫺5
4.63 (18⬚C)
1,10-Phenanthroline NH HN ⫹
Phenylacetic acid
—— 4.91
⫹
CH2CO2H
4.310
—— 1.23 ⫻ 10⫺5
(1.8) 4.92
4.90 ⫻ 10⫺5
4.11 (Continued)
APPENDIX G Acid Dissociation Constants
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Ionic strength () ⴝ 0 Name
Structure
pKa
0.1 M
Ka
pKa
NH3
Phenylalanine
CO2H O
Phosphoric acid* (hydrogen phosphate)
P
HO
6.3 103 4.9 1010
2.18 9.09
2.148 7.198 12.375
7.11 103 6.34 108 4.22 1013
1.92 6.71 11.52
(1.5) 6.78
3 102 1.66 107
—— ——
2.950 5.408
1.12 103 3.90 106
2.76 4.92
5.333 9.731
4.65 106 1.86 1010
5.64 9.74
11.125
7.50 1012
11.08
1.952 (CO2H) 10.640 (NH2 )
1.12 102 2.29 1011
1.89 10.46
2.20 (CO2H) 9.31 (NH3)
CHCH2
OH
OH O
Phosphorous acid (hydrogen phosphite)
HP
OH
OH CO2H
Phthalic acid (benzene-1,2-dicarboxylic acid) Piperazine (perhydro-1,4-diazine)
CO2H NH2
NH2
Piperidine
Proline
H2N
CO2H
N H2
Propanoic acid
CH3CH2CO2H
4.874
1.34 105
4.69
Propenoic acid (acrylic acid)
H2C£CHCO2H
4.258
5.52 105
——
Propylamine
CH3CH2CH2NH3
10.566
2.72 1011
10.64
5.20
6.3 106
5.24
(1.01) (CO2H) 5.39 (NH)
9.8 102 4.1 106
(0.95) 5.21
2.03 (CO2H) 4.82 (NH)
9.3 103 1.51 105
2.08 4.69
—— —— —— ——
—— —— —— ——
Pyridine (azine)
NH
NH
Pyridine-2-carboxylic acid (picolinic acid)
Pyridine-3-carboxylic acid (nicotinic acid)
CO2H HO2C
NH O
Pyridoxal-5-phosphate
HO
O POCH2
HO
Pyrophosphoric acid (hydrogen diphosphate)
O O (HO)2POP(OH)2
CH OH N H
CH3
(0.9) 2.28 6.70 9.40
0.13 5.2 103 2.0 107 4.0 1010
(1.4) (POH) 3.51 (OH) 6.04 (POH) 8.25 (NH)
(0.8) (1.9) 5.94 8.25
*pK3 from A. G. Miller and J. W. Macklin, Anal. Chem. 1983, 55, 684.
AP18
APPENDIX G Acid Dissociation Constants
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Ionic strength () ⴝ 0 Name
Structure
pKa
NH2
Pyrrolidine
11.305
0.1 M
Ka
pKa 12
4.95 10
11.3
NH3
Serine
CHCH2OH CO2H
Succinic acid (butanedioic acid)
HO2CCH2CH2CO2H
2.187 (CO2H) 9.209 (NH3)
6.50 103 6.18 1010
2.16 9.05
4.207 5.636
6.21 105 2.31 106
3.99 5.24
1.987 (pK2 )
1.03 102
1.54
1.857 7.172
1.39 102 6.73 108
1.66 6.85
O
Sulfuric acid (hydrogen sulfate) Sulfurous acid (hydrogen sulfite)
HO
S
OH
O O HOSOH O
Thiosulfuric acid (hydrogen thiosulfate)
(0.6) (1.6)
HOSSH
0.3 0.03
—— (1.3)
O NH3
Threonine
CHCHOHCH3
2.088 (CO2H) 9.100 (NH3)
CO2H
Trichloroacetic acid Triethanolamine Triethylamine 1,2,3-Trihydroxybenzene (pyrogallol)
Cl3CCO2H
(0.5)
(HOCH2CH2)3NH
(CH3CH2)3NH
7.762 10.72
OH
—— —— ——
OH OH
8.17 103 7.94 1010 3
2.20 8.94 ——
8
1.73 10
11
1.9 10 —— —— ——
7.85 10.76 8.96 11.00 (14.0) (20 C)
Trimethylamine
(CH3)3NH
9.799
1.59 1010
9.82
Tris(hydroxymethyl)aminomethane (tris or tham)
(HOCH2)3CNH3
8.072
8.47 109
8.10
NH3
Tryptophan
CHCH2 CO2H
N H
NH3
Tyrosine
CHCH2 CO2H
OH
—— ——
—— ——
2.37 (CO2H) 9.33 (NH3)
—— —— ——
—— —— ——
2.41 (CO2H) 8.67 (NH3) 11.01 (OH)
NH3
Valine
CHCH(CH3)2 CO2H
Water*
H2O
2.286 (CO2H) 9.719 (NH3) 13.997
5.18 103 1.91 1010
2.27 9.52
1.01 1014
——
*The constant given for water is Kw.
APPENDIX G Acid Dissociation Constants
AP19