Etude par HPLC et par spectrophotométrie UV de la réaction de décomposition du carbofuran en milieu aqueux
Written by sctunisie no commentsThe present paper reports the investigation of hydrolysis kinetic of 2,2-dimethyl-2,3-dihydrobenzofuran-7-yl- N-methylcabamate in aqueous media. The determination of 2,2-dimethyl-2,3-dihydrobenzofuranol-7-ol by reversed phase liquid chromatography and spectrophotometric UV titrations, as the adduct of hydrolysis carbamate shows the significant reactivity of the insecticide. The obtained positive entropy ΔS≠ = 73,60 3 mol-1 K-1 and the absence of basic general catalysis indicate an E1cB mechanism involving unimolecular collapse of the carbofuran via a methylisocyanate intermediate. This E1cB process is confirmed by the position of the coordinate (pKa = 10,01 ; log kOH = 1,66) corresponding to the carbofuran point on Brönsted line. The β slope value is -1,10. The Brönsted relation ship is a plot of the rate bimolecular constant logarithm versus the pKa of the conjugate acid of leaving group for a series of substitued N-methylcarbamate which the decomposition mechanism in aqueous media procede via E1cB.
N. Ben Hamida, L. Latrous, S. Sabbah
carbofuran, kinetic, mechanism, HPLC, spectrophotometric UV
Pages 1185-1197
