CIS-TRANS ISOMERISM AND CONFORMATIONAL STRUCTURE OF N-METHYLDODECANELACTAM AS STUDIED BY NMR, IR AND RAMAN-SPECTROSCOPY AND BY THEORETICAL CALCULATIONS

In H-1 and C-13 NMR spectra of N-methyldodecanelactam (I) in CDCl3 and tetrachloroethane solution, the signals of various groups in cis and trans forms of (I) were assigned by means of two-dimensional COSY, HETCOR (heteronuclear correlation spectroscopy) and ROESY methods. The conformational structure of the first two bonds neighbouring the amide bond was determined from J couplings in H-1 NMR spectra and theoretical calculations (MM2, AM1). The barrier to rotation about the amide bond was found from the temperature dependence of lineshapes in H-1 and C-13 NMR spectra. IR and Raman spectra of(I) were measured in the temperature range 25 to - 140 degrees C and the intensity changes of vibrational bands are discussed in connection with possible conformational transitions.