Effect of poly(diallyldimethylammonium chloride) and of poly(ethyleneimine) on the esterolysis of 8-acetoxyquinoline

Abstract

The esterolysis of 8-acetoxyquinoline (8-AQ) in aqueous solution in the presence of an excess of poly(diallyldimethylammonium chloride)(PDDA) or poly(ethyleneimine)(PEI) was investigated at 30°C. In the presence of PDDA hydrolysis takes place and the polyion does not affect the rate of the reaction. In the presence of PEI the ester undergoes aminolysis and saturation kinetics are observed. The pH dependence of k_obs, the apparent first-order rate constant of esterolysis, can be explained on the basis of the pH dependence of pK_app and of the degree of ionization of PEI. A Brønsted relationship has already been found for the aminolysis of 8-AQ with primary and secondary amines of low molecular weight. By extending this relationship to the reaction between the polymeric amino-groups in PEI and 8-AQ, we can quantitatively perdict the pH dependence of K_obs under saturation conditions, provided that the proper values of pK_app of the amino-groups are considered.