Photodegradation of carbaryl by hydroxyl radical theoretically

Abstract

Carbaryl has been degraded in vacuum with hydroxyl radical theoretically using UV light. Different calculation methods like semi-empirical, ab-initio and DFT that’s included quantum mechanics package programs. Optimized structures for all suggested chemical species have been carried out to estimate the reactivity and all chemical properties in the estimated reactions. The probable transition states have been studied through surface potential energy, zero point energy, and first negative frequency of vibration spectrum. Energetic values of all reactions and rate constant of cleavage reaction step are calculated. Total energy, heat of formation and vibration spectrum have been calculated for all suggested reactions component. First degradation reaction of carbaryl is exothermic reaction through C9-O13 bond to give up two major components α-naphthol and carbamic acid radical by activation energy equal to 116.391 kCal mol-1. Rate constant of cleavage step reaction is equal to 2.25 x 1011 s-1. Enthalpy change value of overall degradation reaction equal to -371.674 kCal mol-1. Ten moles of hydroxyl radical are needed to convert carbaryl into simple molecular moieties like CO2, H2CO3, H2O, HNO3 and H2.