The C–Br bond as a main reason for conformational isomerism

The conformational isomerism and orbital interactions of N-(2-bromo-2-phenylethenyl)-N,N-bis(trimethylsilyl)amine and N-(2-bromo-2-trimethylsilylethenyl)-N,N-bis(trimethylsilyl) amine were examined using NMR technique and quantum-chemical calculations. The IR criterion characterizing σ→σ* hyperconjugation is considered, and the linear dependence of σC–H→σ*C–X (X = F, Cl, Br) interaction energy on the polarizability of X is discussed.