Conformational Study of N-Methyl-5,6-dihydro-7H,12H-dibenz[c,f]-azocine by Nuclear Magnetic Resonance Spectroscopy

Abstract

A study of the n.m.r. spectra of N-methyl-5,6-dihydro-7H,12H-dibenz[c,f]azocine, its deuterated derivative, and its conjugate acid in deuteriochloroform and in trifluoracetic acid at 27 and at −62° has shown that the molecule prefers the rigid "crown" conformation. From the equilibrium constant for the equilibrium flexible [Formula: see text] crown at 27 and at −62°, ΔH and ΔS values of −3.2 ± 0.5 kcal/mol and −7 ± 3 e.u. respectively were determined, indicating the preference for the crown conformer. A barrier to interconversion of the flexible to crown form at −62° was determined to be 15.3 ± 0.3 kcal/mol.These parameters provide the first experimental data pertinent to the conformational properties of the 1,4-cyclooctadiene system.