BINDING-ENERGIES AND STRUCTURAL EFFECTS IN HALIDE ANION ROH AND RCOOH COMPLEXES FROM GAS-PHASE EQUILIBRIA MEASUREMENTS

The equilibrium constants for the gas-phase reactions AH plus I** minus equals AHI** minus were measured for compounds where AH equals HOH, MeOH, EtOH, i-PrOH, t-BuOH, HCOOH, MeCOOH, EtCOOH, i-PrCOOH, and t-BuCOOH. van't Hoff plots lead to DELTA G degree //1(300), DELTA H degree //1, and DELTA S degree //1. The observed AHI** minus binding energies are compared with AHF** minus and AHCl** minus results from the literature. The changes of binding energies in ROHF** minus and ROHI** minus are quite different. For ROHF** minus , the binding energies increase linearly with the gas-phase acidities of ROH, such that HOH less than MeOH less than EtOH less than i-PrOH less than t-BuOH. For ROHI** minus , there is an increase only from HOH to MeOH and EtOH while EtOH approximately equals i-PrOH approximately equals t-BuOH. These results illustrate the diminished importance of the polarizability of the alkyl group for the large I** minus ion complexes.