Conformational analysis of some 1 R ,4 S ‐2‐arylidene‐ p ‐menthan‐3‐ones by 1 H NMR spectroscopy and molecular simulation

• Published in: Magnetic resonance in chemistry Vol. 40; no. 9; pp. 566 - 572
• Main Authors: Pivnenko, Nikolay S., Drushlyak, Tatyana G., Kutulya, Lidiya A., Vashchenko, Valeriy V., Doroshenko, Andrey O., Goodby, John W.
• Format: Journal Article
• Language: English
• Published: 01.09.2002
• ISSN: 0749-1581; 1097-458X
• DOI: 10.1002/mrc.1068

Abstract Based on 1 H NMR spectral analysis combined with molecular simulation, conformational states of the cyclohexanone ring were studied for some 1 R ,4 S ‐2‐(4‐X‐benzylidene)‐ p ‐menthan‐3‐ones (X = COOCH 3 or C 6 H 5 ) in CDCl 3 and C 6 D 6 . The co‐existence of chair conformers with an axial orientation of both alkyl substituents and twist‐boat forms was established for the compounds studied at room temperature (22–23° C). The substituent X does not influence appreciably the ratio of these conformers, but the fraction of twist‐boat forms increases noticeably in benzene solutions as compared with CDCl 3 solutions. Rotameric states of the isopropyl fragment were also characterised for the compounds studied. Distinctions in conformational states for the 1 R ,4 S ‐2‐arylidene‐ p ‐menthan‐3‐ones and (−)‐menthone were revealed and are discussed. Copyright © 2002 John Wiley & Sons, Ltd.