Photodecomposition of the Pyrethroid Insecticide

Deltamethrin under Sunlight and UV-Irradiations

M. Farghaly1, S. El-Maghraby1, M. S. Soliman1, B. F. Abdel-Wahab1

and M. A. El-Hashash2

1Department of Applied Organic Chemistry National Research Centre,Dokki,Cairo,Egypt

2Chem. Dept., Faculty of Science Ain Shams University, Cairo, Egypt

Abstract

Photolysis of the Pyrethroid insecticide deltamethrin in various solvents (acetone (3%), methanol, chloroform and benzene) and different surfaces such as upper leaf surface of cotton plant, silica gel, quartz, metal, glass and plastic was studied using ultraviolet and sunlight effects at different periods. Photodegradation of the insecticide in solvents was faster than solid surfaces. The main detected photodegradation products of deltamethrin were 3-phenoxybenzaldehde,3-phenoxybenzoicacid,3-(2,2-dibromoethenyl)-2,2-dimethylcyclopropane carboxylic acid, trans-deltamethrin, cyanohydrin of 3-phenoxybenzaldehyde and des-bromodeltamethrin. Cis-trans isomerization, ester cleavage reactions and loss of bromine are the major processes in the photolysis of (S)-(a-cyano-3-phenoxybenzyl-(1R,3R)-3-(2,2-dibromovinyl)-2,2-dimethylcyclopropane-1-carboxylate (deltamethrin).