Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

It was proved by ¹H and ¹³C NMR spectra that in N-methyl-8-octanelactam in CDCl₃ solution, the amide bond assumes only the cis form. Mirror inversion about the plane of the amide bond occurs with an activation enthalpy ∆H^# = 44.7 kJ/mol. Molecular mechanics and quantum mechanical calculations yielded four favoured conformational structures for the isolated molecule. By vibrational spectra, one of two distinguishable structures strongly predominates. From ¹H NMR spectra, this predominant conformation was identified with one of the calculated stable forms. By ¹³C NMR evidence, poly(N-methyl-8-octanelactam) in tetrachloroethane solution contains equal populations of the cis and trans amide forms; the structure of this polymer in the rubbery solid state seems to be similar to its structure in solution.