Hydrolysis of aryl hydrogen maleate ester mediated by cyclodextrins

GABRIEL O. ANDRES; O. FERNANDO SILVA; RITA H. DE ROSSI

NATL RESEARCH COUNCIL CANADA-N R C RESEARCH PRESS

Año: 2005 vol. 83 p. 1281 - 1281

inetic studies of the hydrolysis of Z-aryl hydrogen maleates (Z = H, p-CH3, m-CH3, p-Cl, m-Cl) were carried out in the presence and absence of hydroxypropyl-â-cyclodextrin (HPCD) at variable pH from 1.00 to 3.00. The reaction involves the formation of maleic anhydride as an intermediate and the rate of its formation is strongly dependent on the pH. This is because the neighboring carboxylate group is a better catalyst than the carboxylic group. The rate constant for the formation of maleic anhydride decreases as the HPCD concentration increases in a nonlinear fashion. The results were interpreted in terms of the formation of a 1:1 inclusion complex of the esters with HPCD. The neutral (HA) and anionic (A) species of the substrate have different association constants (K and K