COOH COOH COOH COOH COOH 0000 CH OH OMe CH pKa 4.57 4.47 4.38 4.17 3.97 C +C +C 邻 COOH COOHCOOH COOH Br CN COOH NO pKa3.973.55 3.51 3.42 C C C C rganIc C emIstry