Hydrolyses of p-acetoxybenzoic acid catalyzed by water-soluble copolymers of N-(5-benzimidazolyl)-acrylamide (BI) were studied at 30° in the neutral pH region in 0.1-1.0 M aqueous KC1 by employing a pH stat. The catalytic hydrolysis conformed to Michaelis-Menten kinetics as in the enzymatic reaction and formation of the catalyst-substrate complex was ascribable to the hydrophobic interaction. In the catalytic hydrolysis with copolymers of BI and vinylpyrrolidone (VP) were observed rate accelerations due to accumulation of thep-hydroxy-benzoate anion in the reaction system. Other undissociated phenols similarly accelerated the catalytic rate. These results were explained by the cooperative action of the BI unit and the phenolic compound bound onto the VP unit. In the catalytic hydrolysis with copolymers of BI and acrylamide (AA), the cooperative esterolytic action of the BI unit was not noted in spite of the intramolecular aggregation of the BI unit observed. Terpolymers containing the BI unit and N-(p-hydroxyphenyl)acrylamide (AP) unit did not show a cooperative catalytic action and the AP unit simply increased hydrophobicity of the catalytic site. The intramolecular aggregation phenomena of these polymer catalysts were discussed on the basis of the hydrophobic nature of monomer units. The modes of aggregation suggested are consistent with the viscometric, potentiometric, and catalytic behavior of the polymer catalysts. The catalytic hydrolysis with 5(6)-acetamidobenzimidazole, a model compound of the BI unit, followed simple second-order kinetics.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry