Hydrogen-Bond Acceptance of Solvents: A 19F Solvatomagnetic β1 Database to Replace Solvatochromic and Solvatovibrational Scales.

A variety of physicochemical properties and several hydrogen-bond donors have been used to define methods and to build scales aiming at measuring the hydrogen-bond acceptance of solvents. There is a great deal of confusion in these scales and methods. Solvatochromic, solvatocalorimetric, solvatovibrational, and 19F solvatomagnetic comparison methods are critically reviewed. Only two methods, the solvatomagnetic and the solvatocalorimetric ones, are able to yield reliable solvent hydrogen-bond acceptance scales. The solvatomagnetic β1 scale defined from the 19F chemical shift of 4-fluorophenol is extended to many solvents including ionic liquids and green solvents. The results for about 240 hydrogen-bond acceptor solvents are organized in a numerical β1 database. The comparison of β1 with solvatochromic scales highlights their shortcomings, in particular for the important class of amphiprotic solvents. Therefore, the use of the 19F solvatomagnetic comparison method and of the solvatomagnetic β1 scale is recommended in solvent effect studies.