Stability of complexes of phenylacetylides and benzyl alkoxides with methanol in the gas phase. Acid-base correlation in the ionic hydrogen-bond strength

The thermodynamic stabilities of methanol-bound phenylacetylides and benzyl alkoxides were determined using a FT-ICR mass spectrometer. The complexation energies between anions and methanol were evaluated from the thermochemical cycle. The complexation energy decreases linearly with increasing acidity of the conjugate acid of an anion, giving slopes of 0.54 and 0.61 for phenylacetylide- and benzyl alkoxide-methanol complexes, respectively. These results show that the linear relationship between the complexation energy and acid-base energetics appears to be a general property in the anion-neutral molecule complexes, but the magnitude of the slope of the linear relationships is not simply related to the structure of the hydrogen-bonded complexes.