New thermochemical parameter for describing solvent effects on IR stretching vibration frequencies. Communication 1. Assessment of van der Waals interactions

Abstract

Solvent effects on O{single bond}H stretching vibrations in several complexes with hydrogen bonding have been investigated by FTIR spectroscopy. To assess the influence of van der Waals (vdW) interactions on frequency shifts, a new parameter of solvent, sqrt(δcav hS), is proposed. This parameter has been derived from equations describing enthalpy of non-specific solvation. Linear correlation was established between the O{single bond}H frequency shift (with respect to the gas phase) and parameter sqrt(δcav hS) for a series of complexes of aliphatic alcohols with standard proton acceptors. Linear correlations with sqrt(δcav hS) were also observed for a series of "free" O{single bond}H and also C{double bond, long}O, P{double bond, long}O, S{double bond, long}O and C{single bond}Br stretching vibrations. A new method is proposed for estimating the gas-phase stretching frequency from IR spectra of solutions. In addition, frequencies of "free" X{single bond}H groups in neat bases were deduced from the experimental data. © 2005 Elsevier B.V. All rights reserved.