Vapor and liquid phase photolysis of the n-butyl ester of 2,4-dichlorophenoxyacetic acid.

The n-butyl ester of 2,4-dichlorophenoxyacetic acid in the liquid and vapor phase was irradiated in a pyrex reactor for 188 hr by ultraviolet light of 300 nm using an intensity similar to that around 300 nm in the solar spectrum. In both phases, the ester was dechlorinated at the ortho position together with simultaneous reduction and Photo-Fries rearrangement to produce volatile photoproducts. Ether bond cleavage to produce chlorophenols, and a Norrish Type II photoprocess, also occurred. A 79% mass balance was accounted for by volatile chlorinated organic residues. HCL gas was also evolved. The production of Cl was also demonstrated in both vapor and liquid phases. The half time of decomposition was around 13 days. The possible effects of the volatile photoproducts on off-target plants were also noted.