Structure—activity relationship for some substituted dialkyl vinyl phosphates

The biological activity against the house fly, Musca domestica L., is reported for a series of dialkyl 2-bromo-1-(2,4-dichlorophenyl)vinyl phosphates. Maximum activity and the lowest degree of synergism with piperonyl butoxide were found with the dimethyl ester. Good activity was also shown by the diethyl ester. Both these compounds, used at the same dose, inhibited fly-head acetylcholinesterase. Compounds with longer alkyl chains were less effective and did not inhibit acetylcholinesterase.