The Conformations of 2-Phenylpropionaldehyde and Some Aliphatic Ketones. The Possible Importance of the CH/π and CH/n Interactions in Determining the Molecular Geometry of a Mobile System

Abstract

Abstract The conformations have been studied by means of NMR spectroscopy, largely by the computer simulation of the lanthanoid-induced shifts, for a series of aliphatic carbonyl compounds with the following structures: CH3CH(C6H5)CO–R; R=H, CH3, C2H5, i-C3H7, and t-C4H9. It has been suggested that two rotamers are important in the conformational equilibria of these ketones, in which the R–C–C–C6H5 dihedral angle is ca. 30° and ca. 90°. The relative stability of the above two rotamers has been found to depend on the nature of the alkyl group, R. The results have been discussed in light of the possible weak attractive forces, the CH/π and CH/n interactions.