Sign reversal of geminal ¹³CH₃—C—¹⁵N coupling in configurationally isomeric fragments

Abstract

The signs of geminal 15 N—C— 13 CH 3 couplings in configurationally isomeric acetophenone oximes have been determined relative to those of the vicinal 15 N—C—C—H interactions using an off resonance proton decoupling technique. In the Z-isomer where the nitrogen lone pair is cis to the coupled carbon, the coupling is large and negative, whereas in the E-isomer, the geminal 15 N—C— 13 CH 3 coupling is small and positive in sign.