Abstract
The dextro, levo and racemic forms of 0-ethyl S-2-(ethylthio) ethyl ethylphosphonothiolate were prepared and examined for insecticidal properties. The lero isomer was about 10 times more toxic to certain insects than the dextro isomer. Also, the levo isomers inactivated fly-brain cholinesterase 11 times faster than the dextro isomer.