| Abstract
| - 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 allowthe determination of whether the other bases react in the same way or as general bases catalyzingthe water reaction. The rate constants for all of them including water and HO- define a Brönstedplot with β = 0.46. The kinetics of the hydrolysis of the esters were studied below pH 6.20, and themechanism involves the formation of phthalic anhydride, which then is hydrolyzed to the phthalicacid. Phenoxide ion has a very high rate constant for the reaction with phthalic anhydride, soabove pH 6.20 it competes significantly with the hydrolysis of the anhydride. The reactions of theesters as a function of pH allow the determination of the kinetic pKa 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 bythe neighboring carboxy group takes place only when it is ionized (i.e., as carboxylate).
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