Values of pK for common alkyl carboxylic acids are around 5(K10). Formula Name Values Simple carboxylic acids K。(at25C) pKa HCOOH formic acid 1.77×104 3.75 CH;COOH acetic acid 1,76×105 474 CH:CH2 COOH propionic acid 1.34×105 4.87 CH(CH2)2COOH butyric acid 154×105 4.82 CH3(CH2)COOH pentanoic acid 1.52×105 4.81 CH3(CH2)4COOH hexanoic acid 131×105 4.88 CH (CH2)COOH octanoic acid 1.28×105 4.89 CH(CH2)COOH decanoic acid 1.43×105 4.84 CHsCOOH benzoic acid 6.46×10 4.19 P-CH;CsH COOH p-toluic acid 433×105 4.36 p-CIC HCOOH p-chlorobenzoic acid 1.04×104 3.98 P-NO2C H4COOH p-nitrobenzoic acid 3.93×104 3.41 Dicarboxylic acids Kal pKal K pK32 HOOC一COOH oxalic 5.4×102 1.27 5.2×105 4.28 HOOCCH2COOH malonic 1.4×103 2.85 2.0×106 5.70 HOOC(CH2)COOH succinic 6.4×105 4.19 2.3×106 5.64 HOOC(CH2)COOH glutaric 4.5×105 4.35 3.8×106 5.42 HOOC(CH2)COOH adipic 3.7×105 4.43 3.9×106 5.41 cis-HOOCCH=CHCOOH maleic 1.0×102 2.00 55×107 6.26 trans-HOOCCH=CHCOOH fumaric 9.6×104 3.02 4.1×103 4.39 1,2-C6H(C0OH)2 phthalic 1.1×103 2.96 4.0×106 540 1,3-C6H(C00H)2 isophthalie 2.4×10 3.62 2.5×105 4.60 1,4-CH(C00H)2 terephthalic 2.9×10 3.54 3.5×105 4.46 Ch20 Carboxylic Acids (landscape) Page 7Ch20 Carboxylic Acids (landscape) Page 7 Values of pKa for common alkyl carboxylic acids are around 5 (Ka ~ 10-5 )