Kinetic and spectroscopic characterization of ternary complexes by numerical fitting methods. Catalysis of acyl-transfer reactions by a macrocyclic azoniacyclophane

Article abstract of DOI:10.1021/ja00073a012

Spectroscopic and computational procedures are presented for the analysis of highly complex kinetic schemes occurring in acyl-transfer reactions which are catalyzed by an azoniacyclophane (CP66). The results, supported by product identification and inhibition experiments, indicate an acyl transfer from intracavity-bound substrates such as 2,4-dinitronaphthyl acetate (DNNA) to hydroxybenzoic acids which are bound as cosubstrates to the positively charged CP66 by electrostatic association. The kinetic system is represented by 11 single steps, including the hydrolysis via a binary complex with CP66 and a side reaction to Meisenheimer products. Seven constants are determined by separate measurements with different techniques; three parameters for the ternary complex are then identified by curve fitting to the observed saturation kinetics. A newly developed numerical integration and optimization program allows the description of all parallel reaction parameters including fast equilibria.