A Revision of the Gutmann Donor Numbers of a Series of Phosphoramides Including Tepa

The donor numbers (DN) of a series of 20 phosphoramides with general structure (R2N)(X2N)(Y2N)P=O (with R,X and Y alkyl radicals, nitrogen-heterocycles or hydrogen atoms) were revised on the basis of a series of rather simple considerations. It is shown that all the phosphoramides considered even after the revision are characterized by high DN. In a scale of 163 different type of solvent molecules, the phosphoramides are all collocated with their DN above 35 Kcal/mol till 50 Kcal/mol. The extremely high DN value reported previously for TEPA, is now revised to 50 Kcal/mol. The highest DN values in the phosphoramides considered were found in (aziridino)3P=O (TEPA), (NHEt)3P=O and in (Pyrrolidino)3P=O.