Studies of polarised ethylenes—IV: Barriers to rotation around formal double bonds and formal single bonds in 1, 1‐bis‐dimethylaminoethylenes

Abstract

Abstract 1, 1‐Bis‐dimethylaminoethylenes with electron attracting substituents on C 2 show rotations around the CC and CN bonds, the rates of which are in most cases measurable by the NMR line shape method. The temperature‐dependent four‐and eight‐site NMR spectra have been analysed and the barriers to rotation around the different bonds have been evaluated by a complete line shape treatment based on the Bloch formalism. Assignment of sites to methyl groups has been made with the aid of aromatic solvent induced shifts and anisotropy effects.