PREVIOUSLY UNREPORTED HOMOLOG OF MALATHION FOUND AS RESIDUE ON CROPS

An unknown compound, thought to be related to malathion, was found as a residue on malathion field-sprayed kale. The same compound was also found in the Malathion, 50% Emulsifiable Concentrate, which was used to prepare the aqueous spray, as shown by similar gas-liquid chromatographic retention times and thin-layer chromatographic Rf values. This observation indicated that the unknown compound was not an alteration product formed after the application of malathion. The compound was isolated and collected from the Malathion, 50% Emulsifiable Concentrate, by gasliquid chromatographic fractionation. By the use of nuclear magnetic resonance and mass spectrometry, the compound was identified as the ethyl butyl mercaptosuccinate, S-ester with O,O-dimethyl phosphorodithioate, a homolog of malathion. The oxygen analog of this compound was five times as inhibitory as the oxygen analog of malathion toward bovine erythrocyte cholinesterase. The parent compound, as determined by gas-liquid and thinlayer chromatographic data, has since been found in one 1968 commercial formulation of malathion, and in samples of grains containing malathion residues. © 1969, American Chemical Society. All rights reserved.