Calorimetric enthalpy data and infrared OH frequency shifts are reported for the acid–base interaction of perfluoro-tert-butyl alcohol with a variety of Lewis bases. A reduced adduct solvation by CCl4 plus an excessive acid solvation leads to lower enthalpies measured in CCl4 solution than in hexane solution. Reaction enthalpies with six donors in hexane were used to evaluate the Ea and Ca parameters for perfluoro-tert-butyl alcohol. Seven other donor enthalpies were calculated using the double scale enthalpy equation. The following correlation was found: ΔH (±0.2) = 0.0106Δv + 3.9. This correlation along with ΔH vs. ΔH correlations with 2,2,2-trifluoroethanol, 1,1,3,3,3,3-hexafluoro-2-propanol, and phenol indicates that van der Waals repulsions are of least importance in the perfluoro-tert-butyl alcohol reactions. The slopes and intercepts of these relations, like the Ea and Ca parameters, reveal the relative electrostatic and covalent contributions in the formation of a hydrogen bond for each of these alcohols. The data adhere nicely to a single-scale enthalpy equation (ΔHa = αAβB) and an α vs. σ∗ plot. This fit provides good evidence for negligible acid–base steric interactions in the perfluoro-tert-butyl alcohol reactions.
ASJC Scopus subject areas
- Colloid and Surface Chemistry