Stereochemical dependence of vicinal H—C—O—H coupling constants

Abstract

The exact analysis of the ABC type absorption due to the —CH 2 OH group of 3β-acetoxy-5β,6β-oxidocholestan-19-ol provides two vicinal HCOH coupling constants for dihedral angles of 80° and 160°. A least squares fit of these and previous data in the literature to a "Karplus" relation provides values for the coefficients in such an equation. The theoretical justification for such a relation has been obtained by extended Hückel molecular orbital calculations for methanol with different dihedral angles. The practical limitations in, and applications of the relation are discussed. An effect of solvent on the vicinal coupling constants is also noted and discussed.