Molecular polarisability. The conformations of pyridine-2-aldehyde, 2-acetylpyridine, and α-pyridil as solutes in benzene

Abstract

Pyridine-2-aldehyde, 2-acetylpyridine, and α-pyridil have dipole moments of 3·35, 2·87, and 4·43 D, respectively, and molar Kerr constants of 578, 396, and –268 × 10^–12. Data for the aldehyde and methyl ketone are consistent with mixtures of planar s-trans- and s-cis-conformers, with the trans-species predominating. The effective conformation of α-pyridil is a skew structure in which the dihedral angle between the C₅H₄N·CO planes is 80–83°; each C₅H₄N·CO moiety is assumed to adopt a flat s-trans arrangement.