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Stability of agricultural chemicals. I.—Hydrolytic and thermal stabilities of phosphorylated crotonamides
Author(s) -
Brown N. P. H.,
Forster A. S.,
Furmidge C. G. L.
Publication year - 1966
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740171107
Subject(s) - hydrolysis , chemistry , decomposition , thermal decomposition , thermal stability , acetone , chemical decomposition , organic chemistry , phosphate , chemical stability , phosphorus
The chemical stability of organo‐phosphorus insecticides is important in determining both the shelf life of their formulations and their rates of decay after application. In common with most organic esters, they are liable to hydrolyse and their stability is considerably impaired by increase in temperature. The hydrolysis of 3‐(dimethoxyphosphinyloxy)‐ N, N ‐dimethyl‐ cis ‐crotonamide (‘Bidrid’*) and the corresponding N ‐monomethyl derivative (‘Azodrin’*) has been examined at various temperatures and under various pH conditions. Rate constants have been calculated and indicate that the alkaline hydrolysis occurs much more rapidly (approximately 17 times) than acidic hydrolysis. The breakdown mechanism differs between the two cases; acidic hydrolysis produces as its main decomposition products methylphosphoric acid and N ‐mono‐ or N , N ‐di‐methylacetoacetamide while alkaline hydrolysis produces dimethyl phosphate, methyl alcohol and acetone. Both materials are highly susceptible to increase in temperature and the rates for this decomposition and their significance have been studied. Both the nature of the decomposition products and the rate of thermal breakdown are affected considerably by small quantities of water and free acid in the insecticide. The results are discussed in relation to the existing literature on the decomposition of organo‐phosphorus insecticides and a mechanism of thermal breakdown for both materials is suggested.