The insecticidal, anticholinesterase, and hydrolytic properties of a series of phosphoramidothiolates were examined with emphasis on structure-activity relationships. These compounds are surprisingly toxic to houseflies although they are not unusually strong inhibitors of cholinesterase. However, in-hibited cholinesterase does not spontaneously recover

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a n d R. 0. M y e r s A series of 0-(diethyl phosphoryl) and 0-(methyl-carbamoy1)oximes of substituted acetophenones and a-substituted benzaldehydes were evaluated for anticholinesterase activity, toxicity to insects, and for chemical reactivity. Multiple regression analysis was used to correlate reactivity and biological data with free energy parameters. Excellent correlation was obtained between electronic effects, reactivity and anticholinesterase activity for the ring-substituted acetophenone 0-(diethyl phosphory1)oximes and 0-(methylcarbamoy1)oximes. With the a-substituted benzaldehyde 0-(methylcarbamoy1)oximes. the addition of Hansch's K constant to the regression equation was necessary to provide correlation with anticholinesterase activity. An unusual example of the Beckmann rearrangement was discovered and the high reactivity of substituted acetophenone @(diethyl phosphory1)oximes containing electrondonating substituents is explained in terms of this rearrangement.ince the report by Hackley er a/. (1959) describing the potent anticholinesterase activity and toxicity of 0-(iso-

Eight pairs of O-methyl and O-ethyl O-(substituted-phenyl) phenylphosphonothionates were evaluated with respect to their delayed neurotoxic activity in hens. O-methyl compounds were in all cases more active than their O-ethyl analogs. The neurotoxic potential of the O-methyl phenylphosphonothionates was 2,5-diCl greater than 4-NO2 greater than 2,4,5-triCl and 2,4,6-triCl greater than 2,4-diCl greater than 2,5-diCl-4-Br greater than 4-CN, when single oral doses were given. Both EPN-ethyl and leptophos-methyl were more neurotoxic in multiple dermal than multiple oral dosing regimens. LD50s for mice and flies were established.