Hydrogen bonding in the gas phase. Part 3.—Infrared spectroscopic investigation of complexes formed by phenol and by 2,2,2-trifluoroethanol

Abstract

An infrared investigation has been made of gas-phase hydrogen-bonded complexes formed by both phenol and 2,2,2-trifluoroethanol. For trifluoroethanol, an investigation of a wide range of O—H ⋯ O complexes shows that the electron donating power of an oxy-group increases along the series, esters, ketones and aldehydes, alcohols and ethers, and for any given class it is increased by increasing methylation. For phenol, investigation of selected complexes shows there is a very close similarity between the wavenumber displacements, Δ^–_ν, for the complexes formed by phenol and trifluoroethanol with any given base, the similarity extending also to a number of O—H ⋯ N complexes.

It is shown that where vapour pressure of a component is a limitation on observing complex formation in the gas-phase, as in the case for phenol, it will generally be advantageous to work at higher temperatures.