Molecular polarisability. The conformations of certain unsaturated ketones as solutes in carbon tetrachloride

Abstract

Observed molar Kerr constants can be reconciled with solute conformations as follows: for mesityl oxide, the acetyl and isopropylidene groups are in planes twisted around the (CO)–(CH:CMe₂) bond by ca. 38° from the s-cis-form; in phorone the planes of the CH:CMe₂ units are twisted oppositely by 52–55° out of the s-cis,s-cis extreme configuration; 3,5-dimethylcyclohex-2-enone, isophorone, and piperitone have near-flat ring skeletons; the C₆-ring of pulegone is puckered, possibly to an extent approaching that in cyclohexane. These conclusions are in essential harmony with those drawn in 1949 by Bentley et al. from dipole measurements.