D. Sen, C. Wells
Jun 1, 1981
Citations
0
Influential Citations
7
Citations
Journal
Pesticide Science
Abstract
Photolysis of 2-dimethylamino-5, 6-dimethylpyrimidin-4-ol (I) in degassed aqueous solution yields two isomeric photo-dimers which are formed by dimerisation across the 5, 6-double bond of I. The yield of dimers is dependent upon the initial concentration of I and on the temperature; this can be explained in terms of a mechanism whereby pyrimidinol aggregates react to give dimers. The formation of aggregates can account for the fact that the quantum yield for the overall reaction of I was higher in degassed acetonitrile than in degassed aqueous solution, it can also account for four photo-dimers being formed in the former solvent and only two in the latter solvent. The photo-dimers revert to I when heated or on photolysis. That photodimers are not formed under natural conditions in the environment is considered to be partly because oxygen may react competitively with photo-excited pyrimidinol species and so prevent dimerisation.