Solvolysis of 4‐acyloxy‐3‐nitrobenzoic acid substrates catalyzed by polyethylenimine derivatives

The solvolytic reactions of anionic activated esters (Sn−) catalyzed by dodecane‐block‐poly[ethylenimine‐graft‐4(5)‐methylimidazole] and related model compounds were investigated. Hydrolysis of 4‐acetyl‐3‐nitrobenzoic acid (S2−) as a function of pH suggested that electrostatic interactions are operative only in the higher molecular weight polymers. Apolar interactions were evident from the greater catalytic rates observed for the hydrolysis of a series of 4‐acetoxy‐3‐nitrobenzoic acid substrates (Sn−). The largest rate enhancements were reflected by catalysts that make effective use of the electrostatic interaction and also provide an apolar binding site. Dodecane‐block‐poly[ethylenimine‐graft‐4(5)‐methylimidazole], with a DP = 85, catalyzed hydrolysis of Sn−(n = 2, 4, and 7), in excess substrate, exhibited saturation kinetics and followed a simple Michaelis‐Menten‐type mechanism. Inhibition of the catalyst in the hydrolysis of S12− was observed and can be rationalized by analogy to certain multisite enzymatic reactions.