SPECTROSCOPIC STUDIES OF ALCOHOLS: III. FUNDAMENTAL OH STRETCHING BANDS OF 2,2-DI- AND 2,2,2-TRI-HALOETHANOLS

Abstract

The OH stretching region was examined for the compounds F3CCH2OH, Cl2CHCH2OH, Cl3CCH2OH, and Br3CCH2OH in dilute CCl4 solution. The first two compounds exhibit temperature-dependent band asymmetry which is due to trans–gauche equilibria arising from rotation about the C—O bond, with relatively small populations in the trans forms. Enthalpy differences of 3.3 and 2.4 kcal/mole between the conformers were obtained for these two compounds respectively. Although symmetrical at lower temperatures, the band for Cl3CCH2OH shows the presence of a small amount of the trans conformer at temperatures above 45 °C. These results are discussed in terms of intramolecular OH … X hydrogen bond interaction, inductive effects, non-bonded interactions, O—H bond polarization, C—X bond polarizability, and the size of the halogen atoms in a geometrically constrained system.