Dehydrochlorination and Insecticidal Action in Chlorinated Hydrocarbons

Abstract

EARLY in the history of D.D.T., Martin and Wain¹ suggested that easy dehydrochlorination is necessary for insecticidal action in chlorinated hydrocarbons. This generalization has since been extended to benzene hexachloride, to chlorinated indanes and terpenes. A new group of insecticides, introduced by Julius Hyman and Co., of Denver, Colorado, provides an exception to this rule. For example, 'Compound 118', stated to be 1,2,3,4,10,10-hexachloro-1 : 4,5 : 8-diendomethano-1,4,4a,5,8,8a-hexahydronaphthalene, is stable to alcoholic potash yet is of the same order of insecticidal activity as D.D.T. Fed to caterpillars of Mamestra brassicœ, it was toxic at 0·14 ± 0·003 mgm. per 0·5 gm. larva, the toxic dose of D.D.T. being 0·06 ± 0·011 mgm. To adult Calandra granaria walking on filter paper impregnated with oil-solutions of the insecticides, the relative magnitude of the median effective doses (D.D.T. : 'Compound 118') was, after 68 hr., 4·5 : 1 ; after 90 hr., 2·5 : 1 ; after 120 hr., 1 : 1 ; and after 140 hr., 0·8 : 1. This difference in speed of action and differences in the reactions of the poisoned insects indicate that the two insecticides are dissimilar in their modes of action.