Effect of cyclodextrin on the hydrolysis of fenitrothion

RAQUEL V. VICO; ELBA I. BUJÁN; RITA H. DE ROSSI

Isla de Margarita

Conferencia; 6ta. Conferencia Latinoamericana de Fisicoquímica Orgánica; 2001

Universidad Central de Venezuela

Cyclodextrins are cyclic oligomers of alfa-D-glucose which are produced by enzimatic degradation of starch. They are capable of forming inclusion complexes with a great variety of compounds, and sa a result of the interaction many reactions have been found to be catalized and others inhibited. We studied the hydrolysis of fenitrothion 1 in water containing 2% ACN at 25ºC, ionic strength 1 M with NaOH 0,1-1.0 M. The observed pseudo-first-order rate constant(kobs) depends linearly on NaOH concentration; the second order rate constant was calculated as 1.98 x 10-3 M-1 s-1. When the reaction was carried out with constant concentration of NaOH and increasing concentration of beta-cyclodextrin kobs diminishes. For the cyclodextrin mediated reactions we suggest that 1 forms inclusion complexes with beta-cyclodextrin in its neutral and ionized form. These complexes are less reactive than the free substrate.