Comparative Analysis of Complexation of Pesticides (fenitrothion, methylparathion, parathion) and their Carboxylic Ester-Analogues by beta-Cyclodextrin. Theoretical Semiempirical Calculations.

E. N. COSCARELLO; D. A. BARBIRIC; E. A. CASTRO; RAQUEL V. VICO; ELBA I. BUJÁN; RITA H. DE ROSSI

J. Struct. Chem.

Springer

Lugar: New York; Año: 2009 vol. 50 p. 671 - 671

0022-4766

he complexation by beta-cyclodextrin (beta-CD) of three organophosphorus pesticides, fenitrothion, parathion and methylparathion, and of their carboxylic ester analogues was analyzed using PM3 and molecular mechanics methods. The objective was to elucidate structural features and energy changes that accompany the complexation and could possibly affect the hydrolysis process, which is catalyzed by beta-CD in the case of carboxylic esters but inhibited for the pesticides, in alkaline medium. The complexation of fenitrothion was further explored, since experiments proved its hydrolysis is relatively less inhibited and progresses mainly through a different pathway than that usually accepted. The results of this study show that complex structures involving esters enable effective interactions between the guest carbonyl and the rim of the host; methylparathion and parathion, however, appear to be deeply included in the cavity of beta-CD. Therefore the conditions for a nucleophilic attack