STEREOCHEMISTRY AND KINETICS OF METHOXIDE ION SUBSTITUTION IN (Z) AND(E)-O-METHYLBENZOHYDROXIMOYL CYANIDES

The stereochemistry and kinetics of the methoxide ion substitution rea ctions (Z)- and (E)-methylbenzohydroximoyl cyanide [PhC(CN)=NOCH3] wer e investigated. The reaction of the (Z)-hydroximoyl cyanide with sodiu m methoxide in DMSO-methanol (9:1) solution at 44.8-degrees-C gives a mixture of methyl (Z)-O-methylbenzohydroximate [PhC(OCH3)=NOCH3] and t he O-methyloxime of alpha-ketophenylacetamide [PhC(CONH2)=NOCH3). The (E)-hydroximoyl cyanide undergoes methoxide ion-catalyzed isomerizatio n to the E-isomer faster than it undergoes nucleophilic substitution. These observations were interpreted in terms of an addition-eliminatio n mechanism in which the rate-limiting step is elimination of the nucl eofuge (A(N) + D(N#)).