Application of Hückel molecular orbital theory to the photodecomposition of pesticidal N-methylcarbamates 1

Abstract

Photodecomposition of pesticidal N-methylcarbamates is examined using simple Hückel Molecular Orbital (HMO) theory. Bond orders and charge densities are calculated for the ground state molecular configurations of these carbamates, and the values used to predict the observed photodecomposition products of carbamate photolyses in both aerated and degassed solutions at excitation wavelengths (λ) greater than 265 nm and 310 nm. It is observed that the experimental products of photodecomposition characterized are almost always the same as those predicted by HMO calculations. Limitations of application of such calculations in predicting photodecomposition products indicate that charge densities and bond orders alone cannot be used in predicting all the observed photodecomposition products and that the ring symmetry and positions of ring substituents may affect the product formation and must be taken into consideration.