Alkaline hydrolysis of ethiofencarb: Kinetic study and mechanism degradation

Abstract

The present paper deals with the hydrolysis of ethiofencarb [2ethylthiomethyl(phenyl)-N-methylcarbamate] in alkaline solution. The reaction kinetics has been investigated using spectrophotometric and liquid chromatographic techniques. The rate constants were determined following a proposed first-order kinetic model. The positive activation entropy S = = +100.07 J mol −1 K −1 and the absence of general basic catalysis indicated an E1cB hydrolytic mechanism, involving the formation of methyl isocyanate. This result was confirmed by the fact that ethiofencarb fits well into Brönsted and Hammett lines, obtained for a series of substituted N-methylcarbamate whose decomposition in aqueous media was established to follow an E1cB mechanism. C 2012 Wiley Periodicals, Inc. Int J Chem Kinet 45: [118][119][120][121][122][123][124] 2013

Kinetic Study and Mechanism Hydrolysis of 4‐Bromo‐3,5 dimethylphenyl N‐methylcarbamate in Aqueous Media

“…The positive value of the activation entropy is in agreement with the mechanism E1cB. Comparable values were obtained for the hydrolysis reaction of a series of N ‐methylcarbamates studied in our laboratory: carbaryl , carbofuran , methiocarb , bendiorab , zectran , aminocarb , landrin , ethiofencarb , carzol , and isoprocarb .…”

“…The positive value of the activation entropy is in agreement with the mechanism E1cB. Comparable values were obtained for the hydrolysis reaction of a series of N-methylcarbamates studied in our laboratory: carbaryl [3], carbofuran [4], methiocarb [5], bendiorab [6], zectran [7], aminocarb [8], landrin [9], ethiofencarb [10], carzol [11], and isoprocarb [12]. The Brönsted line log k OH = β pK a + cte, which relates the logarithm of the bimolecular rate constant to the pK a of the leaving group, can be used to elucidate the mechanism of the BDMC hydrolysis.…”

“…The corresponding mechanism involves either an addition of OH − into the carbonyl with a further elimination of the RO − leaving group or an abstraction of the hydrogen of the methylcarbamate moiety again evolving with the elimination of the RO − group. Consequently, we have undertaken in our laboratory a study of the determination of both the kinetic and mechanistic aspects of the hydrolysis reaction of carbaryl , carbofuran , methiocarb , bendiocarb , zectran , aminocarb , landrin , ethiofencarb , carzol , isoprocarb , and pirimicarb . We showed that hydrolysis of PNMCs exhibited pseudo–first‐order kinetics with respect to substrate in aqueous media.…”

Kinetics and Mechanism of Degradation of Aqueous Promecarb Insecticide Studied by UV Spectrophotometry and HPLC

“…So there is no general base catalysis and the E2 mechanism can be eliminated. These results are consistent with those obtained for bendiocarb, Zectran, methiocarb, ethiofencarb and landrin [22][23][24][25].…”

Predicting Reactivities of Phenyl N-methylcarbamates in their Alkaline Hydrolysis

“…The main pathway of this transformation is hydrolysis since the common structural feature of N-methylcarbamates is a N-methyl group that can be easily hydrolysed to form methylamine and the corresponding phenols in alkaline media. Consequently we have undertaken a study of the determination of both kinetic and mechanistic aspects of the hydrolysis of PNMCs such as carbaryl [3], carbofuran [4], methiocarb [5], bendiocarb [6], aminocarb [7], zectran [8] and landrin [9]. We showed that hydrolysis of PNMCs exhibited pseudo-first order kinetics with respect to substrate in aqueous media.…”