CH:COOH CH CH,COOH (CH:),CHCOOH (CH3)CCOOH pKs 4.76 4.86 4.87 5.02 强 弱 COOH CH2COOH CH2CH2COOH COOH CH2COOH CH2CH2COOH 1.46 4.17 4.43 强 弱 品 COOH COOH COOH COOH NO2 NO2 pKa 2.21 3.40 3.46 4.17 CH3COOH CH3CH2COOH (CH3 )2CHCOOH (CH3 )3CCOOH pKa 4.76 4.86 4.87 5.02 强 弱 COOH COOH CH2CH2COOH CH2CH2COOH CH2COOH CH2COOH pKa1 1.46 4.17 4.43 强 弱 pKa 2.21 3.40 3.46 4.17 COOH NO2 COOH NO2 COOH NO2 COOH