harxxxxx_App-G.qxd 3/8/10 1:34 PM Page AP11 APPENDIX G Acid Dissociation Constants §␮ ϭ 0.1 M 0 ؍ (Ionic strength (␮ † ‡ † Name Structure* pKa Ka pKa ϫ Ϫ5 Acetic acid CH3CO2H 4.756 1.75 10 4.56 (ethanoic acid) N ϩ H3 ϫ Ϫ3 Alanine CHCH3 2.344 (CO2H) 4.53 10 2.33 ϫ Ϫ10 9.868 (NH3) 1.36 10 9.71 CO2H ϩ Ϫ5 Aminobenzene NH3 4.601 2.51 ϫ 10 4.64 (aniline) ϪO SNϩ Ϫ4 4-Aminobenzenesulfonic acid 3 H3 3.232 5.86 ϫ 10 3.01 (sulfanilic acid) ϩ NH3 ϫ Ϫ3 2-Aminobenzoic acid 2.08 (CO2H) 8.3 10 2.01 ϫ Ϫ5 (anthranilic acid) 4.96 (NH3) 1.10 10 4.78 CO2H ϩ 2-Aminoethanethiol HSCH2CH2NH3 —— 8.21 (SH) (2-mercaptoethylamine) —— 10.73 (NH3) ϩ ϫ Ϫ10 2-Aminoethanol HOCH2CH2NH3 9.498 3.18 10 9.52 (ethanolamine) O H ϫ Ϫ5 4.70 (NH3) (20°) 2.0 10 4.74 2-Aminophenol Ϫ 9.97 (OH) (20°) 1.05 ϫ 10 10 9.87 ϩ NH3 ϩ ϫ Ϫ10 Ammonia NH4 9.245 5.69 10 9.26 N ϩ H3 N ϩ H2 ϫ Ϫ2 1.823 (CO2H) 1.50 10 2.03 CHCH CH CH NHC ϫ Ϫ9 Arginine 2 2 2 8.991 (NH3) 1.02 10 9.00 NH —— (NH2) —— (12.1) CO2H 2 O Ϫ 2.24 5.8 ϫ 10 3 2.15 Ϫ Arsenic acid HO As OH 6.96 1.10 ϫ 10 7 6.65 Ϫ (hydrogen arsenate) (11.50) 3.2 ϫ 10 12 (11.18) OH ϫ Ϫ10 Arsenious acid As(OH)3 9.29 5.1 10 9.14 (hydrogen arsenite) N ϩ O H3 Asparagine CHCH2CNH2 —— —— 2.16 (CO2H) —— —— 8.73 (NH3) CO2H *Each acid is written in its protonated form. The acidic protons are indicated in bold type. † Њ 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). Ϫ ‡ ϭ Ϫ ϭ pKb The accurate way to calculate Kb for the conjugate base is pKb 13.995 pKa and Kb 10 . § ␮ ␮ See marginal note on page 166 for distinction between pKa at 0 and at 0.1 M. (Continued) APPENDIX G Acid Dissociation Constants AP11 harxxxxx_App-G.qxd 2/15/10 5:25 PM Page AP12 ␮ ϭ 0.1 M 0 ؍ (Ionic strength (␮ Name Structure pKa Ka pKa NHϩ 3 ␣ ϫ Ϫ2 ␤ 1.990 ( -CO2H) 1.02 10 1.95 CHCH CO ␤ ϫ Ϫ4 Aspartic acid 2 2H 3.900 ( -CO2H) 1.26 10 3.71 Ϫ 10.002 (NH ) 9.95 ϫ 10 11 9.96 ␣ 3 CO2H ϩ ϫ Ϫ9 —— Aziridine NH2 8.04 9.1 10 (dimethyleneimine) CO Ϫ3 2H 2.86 1.38 ϫ 10 2.67 CO Ϫ5 Benzene-1,2,3-tricarboxylic acid 2H 4.30 5.0 ϫ 10 3.91 Ϫ (hemimellitic acid) 6.28 5.2 ϫ 10 7 5.50 CO2H CO Ϫ5 Benzoic acid 2H 4.202 6.28 ϫ 10 4.01 CH N ϩ Ϫ10 Benzylamine 2 H3 9.35 4.5 ϫ 10 9.40 —— —— (1.3) Ј ϫ Ϫ5 2,2 -Bipyridine N N 4.34 4.6 10 4.41 HϩϩH Ϫ 9.237 5.79 ϫ 10 10 8.98 Ϫ13 Boric acid B(OH)3 (12.74) (20°) 1.82 ϫ 10 —— Ϫ (hydrogen borate) (13.80) (20°) 1.58 ϫ 10 14 —— ϫ Ϫ3 Bromoacetic acid BrCH2CO2H 2.902 1.25 10 2.71 ON NO H H Ϫ Butane-2,3-dione dioxime 10.66 2.2 ϫ 10 11 10.45 Ϫ (dimethylglyoxime) CH (12.0) 1 ϫ 10 12 (11.9) CH3 3 ϫ Ϫ5 Butanoic acid CH3CH2CH2CO2H 4.818 1.52 10 4.62 CO 2H Ϫ cis-Butenedioic acid 1.92 1.20 ϫ 10 2 1.75 Ϫ7 (maleic acid) CO 6.27 5.37 ϫ 10 5.84 2H CO2H Ϫ trans-Butenedioic acid 3.02 9.5 ϫ 10 4 2.84 Ϫ (fumaric acid) 4.48 3.3 ϫ 10 5 4.09 HO2C ϩ ϫ Ϫ11 Butylamine CH3CH2CH2CH2NH3 10.640 2.29 10 10.66 O Ϫ Carbonic acid* 6.351 4.46 ϫ 10 7 6.13 ϫ Ϫ11 (hydrogen carbonate) HO C OH 10.329 4.69 10 9.91 ϫ Ϫ3 Chloroacetic acid ClCH2CO2H 2.865 1.36 10 2.69 ϫ Ϫ5 3-Chloropropanoic acid ClCH2CH2CO2H 4.11 7.8 10 3.92 Ϫ Chlorous acid HOCl£O 1.96 1.10 ϫ 10 2 —— (hydrogen chlorite) ϩ *The concentration of “carbonic acid” is considered to be the sum [H2CO3] [CO2(aq)]. See Box 6-4. AP12 APPENDIX G Acid Dissociation Constants harxxxxx_App-G.qxd 2/15/10 5:25 PM Page AP13 ␮ ϭ 0.1 M 0 ؍ (Ionic strength (␮ Name Structure pKa Ka pKa O Chromic acid HO Cr OH (Ϫ0.2) (20°) 1.6 (Ϫ0.6) (20ЊC) ϫ Ϫ7 6.05 (hydrogen chromate) O 6.51 3.1 10 ϫ Ϫ4 Citric acid CO2H 3.128 7.44 10 2.90 Ϫ5 (2-hydroxypropane-1,2,3- 4.761 1.73 ϫ 10 4.35 O CCH CCH CO Ϫ7 tricarboxylic acid) H 2 2 2 2H 6.396 4.02 ϫ 10 5.70 OH ϫ Ϫ3 Cyanoacetic acid NCCH2CO2H 2.472 3.37 10 —— ϩ ϫ Ϫ11 Cyclohexylamine NH3 10.567 2.71 10 10.62 N ϩ Ϫ2 H3 (1.7) (CO2H) 2 ϫ 10 (1.90) Ϫ Cysteine 8.36 (SH) 4.4 ϫ 10 9 8.18 CHCH SH Ϫ11 2 10.74 (NH3) 1.82 ϫ 10 10.30 CO2H ϫ Ϫ2 Dichloroacetic acid Cl2CHCO2H (1.1) 8 10 (0.9) ϩ ϫ Ϫ11 Diethylamine (CH3CH2)2NH2 11.00 1.0 10 11.04 OH Ϫ 1,2-Dihydroxybenzene 9.45 3.5 10 10 9.26 (catechol) —— —— (13.3) OH OH 1,3-Dihydroxybenzene —— —— 9.30 (resorcinol) —— —— 11.06 OH OH Ϫ4 D-2,3-Dihydroxybutanedioic HO2CCHCHCO2H 3.036 9.20 ϫ 10 2.82 Ϫ5 acid (D-tartaric acid) 4.366 4.31 ϫ 10 3.97 OH HOCH CHCH SH 2,3-Dimercaptopropanol 2 2 —— —— 8.63 SH —— —— 10.65 ϩ ϫ Ϫ11 Dimethylamine (CH3)2NH2 10.774 1.68 10 10.81 NO2 Ϫ 2,4-Dinitrophenol 4.114 7.69 ϫ 10 5 3.92 O2N OH Њ Ethane-1,2-dithiol HSCH2CH2SH —— —— 8.85 (30 C) —— —— 10.43 (30ЊC) ϩ ϫ Ϫ11 Ethylamine CH3CH2NH3 10.673 2.12 10 10.69 ϩϩ Ϫ7 Ethylenediamine NCH CH N 6.848 1.42 ϫ 10 7.11 H3 2 2 H3 Ϫ10 (1,2-diaminoethane) 9.928 1.18 ϫ 10 9.92 (Continued) APPENDIX G Acid Dissociation Constants AP13 harxxxxx_App-G.qxd 2/15/10 5:25 PM Page AP14 ␮ ϭ 0.1 M 0 ؍ (Ionic strength (␮ Name Structure pKa Ka pKa ␮ϭ —— (CO2H) —— (0.0) (CO2H) ( 1 M) ϩ ϩ —— (CO2H) —— (1.5) (CO2H) ( O CCH ) N CH CH N (CH CO ) Ethylenedinitrilotetraacetic H 2 2 2 H 2 2 H 2 2H 2 —— (CO2H) —— 2.00 (CO2H) —— (CO2H) 2.69 (CO2H) acid (EDTA) —— Ϫ 6.273 (NH) 5.3 ϫ 10 7 6.13 (NH) Ϫ 10.948 (NH) 1.13 ϫ 10 11 10.37 (NH) ϫ Ϫ4 Formic acid HCO2H 3.744 1.80 10 3.57 (methanoic acid) NHϩ 3 ␣ ϫ Ϫ3 ␥ 2.160 ( -CO2H) 6.92 10 2.16 CHCH CH CO ␥ ϫ Ϫ5 Glutamic acid 2 2 2H 4.30 ( -CO2H) 5.0 10 4.15 Ϫ 9.96 (NH ) 1.10 ϫ 10 10 9.58 ␣ 3 CO2H N ϩ O H3 Glutamine CHCH2CH2CNH2 —— —— 2.19 (CO2H) —— —— 9.00 (NH3) CO2H ϩ NH3 CH ϫ Ϫ3 Glycine 2 2.350 (CO2H) 4.47 10 2.33 ϫ Ϫ10 (aminoacetic acid) 9.778 (NH3) 1.67 10 9.57 CO2H ϩ NH2 Guanidine —— —— (13.5) (␮ϭ1 M) H2N CNH2 Ϫ 1,6-Hexanedioic acid 4.424 3.77 ϫ 10 5 4.26 HO2CCH2CH2CH2CH2CO2H Ϫ (adipic acid) 5.420 3.80 ϫ 10 6 5.04 O O Ϫ Hexane-2,4-dione 9.38 4.2 ϫ 10 10 9.11 (20ЊC) CH 3CCH2CCH2CH3 NHϩ 3 NH ϫ Ϫ2 (1.6) (CO2H) 3 10 (1.7) CHCH ϫ Ϫ6 Histidine 2 ϩ 5.97 (NH) 1.07 10 6.05 N ϫ Ϫ10 H 9.28 (NH3) 5.2 10 9.10 CO2H ϩ ϩ Ϫ Ϫ 1 Hydrazine H3N NH3 0.99 1.0 ϫ 10 (Ϫ0.21) (␮ϭ0.5 M) Ϫ 7.98 1.05 ϫ 10 8 8.07 ϩ Ϫ Ϫ Hydrazoic acid HNNN 4.65 2.2 ϫ 10 5 4.45 (hydrogen azide) Ϫ Hydrogen cyanate HOCΩN 3.48 3.3 ϫ 10 4 —— Ϫ Hydrogen cyanide HCΩN 9.21 6.2 ϫ 10 10 9.04 Ϫ Hydrogen fluoride HF 3.17 6.8 ϫ 10 4 2.94 Ϫ Hydrogen peroxide HOOH 11.65 2.2 ϫ 10 12 —— ϫ Ϫ8 Hydrogen sulfide H2S 7.02 9.5 10 6.82 Ϫ 14.0* 1.0 ϫ 10 14* —— Hydrogen thiocyanate HSCΩN(Ϫ1.1) (20°C) 1.3 ϫ 101 —— ϫ Ϫ4 Hydroxyacetic acid HOCH2CO2H 3.832 1.48 10 3.62 (glycolic acid) Ϫ Ϫ *D. J. Phillips and S. L. Phillips. “High Temperature Dissociation Constants of HS and the Standard Thermodynamic Values for S2 ,” J.