Effect of cyclodextrins on the reactivity of fenitrothion

NATALIA M. ROUGIER; DYANNE L. CRUICKSHANK; RAQUEL V. VICO; SUSAN A. BOURNE; MINO R. CAIRA; ELBA I. BUJÁN; RITA H. DE ROSSI

CARBOHYDRATE RESEARCH

ELSEVIER SCI LTD

Año: 2011 vol. 346 p. 322 - 327

0008-6215

The hydrolysis reaction of fenitrothion was studied in water containing 2% dioxane and in the presence of native cyclodextrins (alfa-, beta- and ganma-CD) and two commercially available modified derivatives, namely, permethylated beta- and alfa-cyclodextrin (TRIMEB and TRIMEA, respectively). The kinetics of the reaction in the presence of TRIMEA could not be measured because the complex formed is insoluble and precipitated even at low concentration. On the other hand, the reaction is only weakly affected by the presence of alfa-CD. The hydrolysis reaction is inhibited by all the other cyclodextrins. From the kinetic data the association equilibrium constants for the formation of the 1:1 inclusion complexes were determined as 417, 511 and 99 M-1 for beta-CD, TRIMEB and ganma-CD, respectively. Despite the differences in the association constants for beta- and ganma-CD, the observed inhibition effect is about the same and this is due to the fact that the rate of hydrolysis in the cavity of c-CD is smaller than that in the cavity of beta-CD. The strongest inhibitor is TRIMEB and this result is consistent with the known structure of the complex in the solid state.