Preferential Solvation and Hydrogen Bonding in Mixed Solvents

摘要

The molecular-recognition events that underpin many processes in chemistry and biology are intimately linked to accompanying changes in solvation. The subtle interplay of the different factors that contribute fo these changes in solvation gives rise to phenomena that are difficult to interpret at the molecular level. However, a detailed understanding of these effects is essential for the development of quantitative approaches to the analysis of non-covalent molecular interactions in solution. We recently introduced the 1:1 complex formed between tri-n-butylphos-phine oxide (1) and perfluoro-tert-butanol (2; Scheme 1) as a simple probe of solvent effects on molecular interactions. This complex contains a single hydrogen bond between an exceptionally strong H-bond acceptor and an exceptionally strong H-bond donor, so that complexation can be detected in even the most competitive solvent environments. This system not only provides new opportunities to investigate how solvents affect the properties of molecular interactions, but also provides a new probe for studying the nature of the solvent itself and the interactions that govern the properties of the liquid state. Herein we describe experiments on solvent mixtures of chloroform and tetrahydrofuran, a liquid mixture that shows strong deviations from ideality and does not obey regular solution theory.