Conformational analysis of the cis- and trans-1,2-bis(trimethylsilyl)cyclohexanes (BTMSC): molecular mechanics calculations and nuclear magnetic resonance spectroscopy. A preferred diaxial conformation for the trans-isomer

• DOI: 10.1039/a607563k
• Publication Date: 2002-07-26T09:06:44Z
• Authors: Roberto Núñez; Rayomand J. Unwalla; Frank K. Cartledge; Soo G. Cho; Bruce H. Riches; Matthew P. Glenn; Natasha L. Hunger...; Lynette K. Lambert; Douglas J. Brecknell; William Kitching
• Keywords: Cyclohexanes; Trimethylsilyl

Molecular mechanics calculations (MM3-92) suggest that a slightly distorted diaxial chair conformation of trans-1,2-bis(trimethylsilyl)cyclohexane is at least 1.26 kcal mol-1 (1 cal = 4.184 J) lower in steric energy than the diequatorial form, and this supported by NOED spectra, magnitudes vic-1H–1H spin coupling constants, low temperature (190 K) 13C NMR spectroscopic measurements, which place free difference between 1.5 1.7 mol-1.