| Abstract | Ion-molecule complexes of acetylide anions, RCC- (R = tert-butyl, H, phenyl, p-tolyl), and methanol have been studied using Fourier transform ion cyclotron resonance mass spectrometry. The RCC- complexation energies with HOCH3 were measured relative to CH3O-. H2O and CH3O-. HOCH3. These complexes, RCC-. HOCH3, all have complexation energies of -21 kcal/mol and are, therefore, hydrogen-bonded. The acetylides vary in basicity over an 8 kcal/mol range, but all have the same complexation energy with methanol. These results show that the frequently observed relationship between acid-base energetics and complexation energy is a property of the specific system and not:a general one. Thus, the existence, and magnitude, of these correlations cannot be used to infer structural information about the complexes. The stability of hydrogen-bonded complexes appears to be related to the charge distributions of the separated ion and neutral. |
