Phototransformation of some pesticides

Pesticide Residue Laboratory, Department of Agricultural Chemistry & Soil Science,

Bidhan Chandra Krishi Viswavidyalaya, Mohanpur-741 252, India

Manuscript received 26 August 1999

The photochemical transformation of two fungicides, viz. fenarimol (1) and chlorothalonil (6), two herbicides, viz., met-sulfuron methyl (15) and fluchloralin (20), and one insecticide, imidacloprid (26) has been carried out, the results of which form the subject-matter of the present review article. The degradation products are characterized on the basis of spectroscopic evidence. The use of sensitizers like TiO₂, KNO₃, H₂O₂ is observed to enhance the photolytic rate. The results indicate that some of the photometabolites could also be formed through biotic processes. It also reveals that photochemical transformation leads to detoxification of the pesticidal molecules. The phototransformation processes involve N-dealkylation, nitro group reduction, cyclization, dimerization, oxidative cleavage, homolytic cleavage, dechlorination, decarboxylation and dehydration types of reactions.