On the purported axial preference in 2-methylthio and 2-methoxycyclohex-anones: steric effects versus orbital interactions

Autor:	Neil C. Faibish, Robert R. Fraser
Rok vydání:	1995
Předmět:	Steric effects Cyclohexane Stereochemistry Organic Chemistry Substituent General Chemistry Catalysis Solvent chemistry.chemical_compound Crystallography symbols.namesake Dipole chemistry symbols van der Waals force Conformational isomerism Equilibrium constant
Zdroj:	Canadian Journal of Chemistry. 73:88-94
ISSN:	1480-3291 0008-4042
DOI:	10.1139/v95-013
Popis:	The value for the equilibrium constant representing the ratio of equatorial to axial conformers for 2-methylthio- and 2-methoxycyclohexanone has been measured in five solvents using 500 MHz 1H nuclear magnetic resonance. In cyclohexane solvent, the methylthio group is found to have a large axial preference while that for the methoxy is negligible. For both compounds the equilibrium shows a strong solvent dependence. Comparison of these results with those known for the halo derivatives shows the amount of axial to increase in the order: fluoro, methoxy, chloro, bromo, and methylthio. With the aid of molecular mechanics calculations it is concluded that the order of conformational preference can be attributed to a variation in the van der Waals interaction between the substituent and the carbonyl group in the equatorial conformer. Keywords: α-substituted cyclohexanones, conformation, MMX calculations, steric and dipolar effects.
Databáze:	OpenAIRE
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