The structuredness of solvents

The parameterization of the structuredness of a solvent as the difference between its molar heat of vaporization, Δ_vap H ^° and the sum of its internal donor-acceptor interactions (in terms of DN and AN) and its vdW interactions (in terms of Δ_vap H ^° of n-alkanes of the same molar volume) is criticized. As an alternative, the excess of the reduced Trouton constant, Δ_vapS^°/R over 12 and of Kirkwood's dipole correlation parameter g over 1.7 are suggested as criteria for the decision of whether a solvent is structured, both having to be met. Conversely, if either Δ_vapS^°/R is less than 11.6 or g is less than 1.3, then the solvent is to be considered unstructured. Exceptions are discussed.