Ab initio and DFT study of aliphatic diamines

The optimized minimum-energy geometries of different aliphatic diamines and of their protonated forms were determined using ab initio methods and density functionnal calculations. The molecular structures, vibrational frequencies and charge distributions of selected diamines and their protonated forms were also studied. The computed gas phase acidities as measured by the proton affinities of the diamines were obtained. Most methods used were able to predict it well, typically to within 10 kcal mol(-1). (C) 2002 Elsevier Science B.V. All rights reserved.