Gutmann donor numbers applications

Many physical chemists have embraced the concepts of donicity (donor numbers, DN) and acceptor numbers (AN) as developed by Gutmann and his co-workers [12], The DN is measured by the heat of reaction of the donor solvent and antimony pentachloride in a 1 1 ratio as a dilute solution in 1,2-dichloro-ethane. It is taken to be a measure of the strength of the Lewis base. The AN is measured as the relative shift of the 31P NMR peak in triethylphosphine oxide dissolved in the sample solvent. Hexane is given the value of zero on the scale, and antimony pentachloride is given the value of 100. The AN is taken to be a measure of the strength of the Lewis acid. The applications of the concepts have... 

Donor numbers are considered as semiquantitative measures of solute/EPD solvent interactions, and are particularly useful in the prediction of other EPD/EPA interactions in coordination chemistry. Numerous examples of the application of donor numbers have been given by Gutmann [26, 27, 30] cf. also [113, 133]. It has been shown that donor number correlations are parallel with correlations based on the highest occupied molecular orbital (HOMO) eigenvalues of EPD solvent molecules [139], For non-HBD solvents, a fair correlation has been obtained between their donor numbers and their gas-phase proton affinities FA, indicating that the DN values do indeed reflect the intrinsic molecular properties of EPD solvents [140]. 

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