RESUMO
Gas-phase basicities of four polyfunctional N1,N1-dimethyl-N2-azinylformamidines (1-4) are obtained from proton-transfer equilibrium constant determinations, using Fourier transform ion-cyclotron resonance mass spectrometry. Comparison with model amidines and azines (GB revised according to the recent compilation of Hunter and Lias) indicates the aza group as the favored site of protonation. The strong basicity of ortho derivatives is explained in term of intramolecular stabilization (the so-called "internal solvation").
RESUMO
Semiempirical calculations (AM1) together with experimental mass spectrometric (FT-ICR) data indicate the imino nitrogen atom as the favoured site of protonation and the amino nitrogen atom as the site of deprotonation of the amidine group in the gas phase. For tautomerizing N-methyl-N'-phenylbenzamidine the tautomer with the phenyl group at the imino nitrogen atom weakly predominates in tautomeric mixture.