NMR CONFORMATIONAL ISOMERIZATION STUDIES IN SOME 6-MEMBERED HETEROCYCLIC COMPOUNDS

Analysis of low temperature line broadening in the NMR spectrum of 1,1,4,4-tetramethyl-1,4-disilacyclohexane suggests that some exchange broadening may be occurring. The kinetic process is attributed to chair-to-chair conformational isomerization. The barrier to inversion is estimated to be < 6 kcal/mole. It is suggested that the low barrier is due mostly to the greater length of the carbon-silicon bonds. The barrier in N,N,N′,N′-tetramethylpiperazinium diiodide was found to have a ΔFcb‡ 12·7 kcal/mole. © 1969.