Andrés G O, Granados A M, de Rossi R H
Instituto de Investigaciones en Físico Química de Córdoba (INFIQC), Facultad de Ciencias Químicas, Departamento de Química Orgánica, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
J Org Chem. 2001 Nov 16;66(23):7653-7. doi: 10.1021/jo010499v.
The kinetics of the hydrolysis of phthalic anhydride and X-phenyl hydrogen phthalate (X = H, p-Me, m-Cl, and p-Cl) were studied. Several bases accelerate the reaction of phthalic anhydride: acetate, phosphate, N-methyl imidazole, 1,4-diazabicyclo[2,2,2]octane (DABCO), and carbonate. Phosphate, DABCO, and N-methyl imidazole react as nucleophiles, whereas the data do not allow the determination of whether the other bases react in the same way or as general bases catalyzing the water reaction. The rate constants for all of them including water and HO- define a Brönsted plot with beta = 0.46. The kinetics of the hydrolysis of the esters were studied below pH 6.20, and the mechanism involves the formation of phthalic anhydride, which then is hydrolyzed to the phthalic acid. Phenoxide ion has a very high rate constant for the reaction with phthalic anhydride, so above pH 6.20 it competes significantly with the hydrolysis of the anhydride. The reactions of the esters as a function of pH allow the determination of the kinetic pK(a) which are 3.06, 3.02, 2.95, and 2.93 for X = H, p-Me, m-Cl, and p-Cl, respectively. The data also show that the catalysis by the neighboring carboxy group takes place only when it is ionized (i.e., as carboxylate).
研究了邻苯二甲酸酐和邻苯二甲酸氢X-苯酯（X = H、对甲基、间氯和对氯）的水解动力学。几种碱可加速邻苯二甲酸酐的反应：乙酸盐、磷酸盐、N-甲基咪唑、1,4-二氮杂双环[2.2.2]辛烷（DABCO）和碳酸盐。磷酸盐、DABCO和N-甲基咪唑作为亲核试剂反应，而数据无法确定其他碱是否以相同方式反应或作为催化水反应的广义碱。包括水和HO-在内的所有这些物质的速率常数定义了一条β = 0.46的布仑斯惕曲线。在pH 6.20以下研究了酯的水解动力学，其机理涉及邻苯二甲酸酐的形成，然后邻苯二甲酸酐水解为邻苯二甲酸。酚氧离子与邻苯二甲酸酐反应的速率常数非常高，因此在pH 6.20以上，它与酸酐的水解有显著竞争。酯的反应作为pH的函数可以确定动力学pKa，对于X = H、对甲基、间氯和对氯，其动力学pKa分别为3.06、3.02、2.95和2.93。数据还表明，相邻羧基的催化作用仅在其电离时（即作为羧酸盐）发生。
