Conformational analysis. LXXVIII. The conformation of phenylcyclohexane, and related molecules.

✍ Scribed by N.L. Allinger; M.T. Tribble

• Publisher: Elsevier Science
• Year: 1971
• Tongue: French
• Weight: 206 KB
• Volume: 12
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)97150-3

✦ Synopsis

The recent appearance of a paper describing an experimental nmr study by B. L. Shapiro and coworkers3 prompts us to report some of our calculations on molecules which contain a phenyl group attached to a cyclohexane ring. These calculations were carried out with the aid of a force field method previously described, 4 to which must be added only a few numerical constants characteristic of the phenyl group which were also worked out earlier. 5 Shapiro suggested that 3-phenyl-3,5,5-trimethylcyclohexanone had a conformation in which the phenyl group was in an axial position. Since the conformational energy of the phenyl (3.0 kcal/mole') is larger than that of the methyl (1. 7 kcal/mole6), this is quite unexpected. No explanation for this anomaly was offered. For phenylcyclohexane itself, one needs to consider four conformations with the ring in the chair form. Equatorial Perpendicular e01R Equatorial Axial Parallel Perpendicular e0 II R a0lR Axial Parallel a0 IIR The phenyl group can be equatorial or axial, and it can be oriented so that the plane of the phenyl is either perpendicular to the bond connecting the cyclohexane substituent attached