Relative and absolute bond dissociation energies of sodium cation-alcohol complexes determined using competitive collision-induced dissociation experiments

Absolute (R₁OH)Na⁺-(R₂OH) and relative Na⁺-(ROH) bond dissociation energies are determined experimentally by competitive collision-induced dissociation of (R₁OH)Na ⁺(R₂OH) complexes with xenon in a guided ion beam mass spectrometer. The alcohols examined include ethanol, 1-propanol, 2-propanol, n-butanol, iso-butanol, sec-butanol, and tert-butanol, which cover a range in Na⁺ affinities of only 11 kJ/mol. Dissociation cross sections for formation of Na⁺(R₁OH) + R₂OH and Na ⁺(R₂OH) + R₁OH are simultaneously analyzed with a model that uses statistical theory to predict the energy dependent branching ratio. The cross section thresholds thus determined are interpreted to yield the 0 K (R₁OH)Na⁺-(R₂OH) bond dissociation energies and the relative 0 K Na⁺-(ROH) binding affinities. The relative binding affinities are converted to absolute 0 K Na⁺-(ROH) binding energies by using the absolute bond energy for Na⁺-C ₂H₅OH determined previously in our laboratory as an anchor value. Comparisons are made to previous experimental and theoretical Na ⁺-(ROH) thermochemistry from several sources. The absolute (R ₁OH)Na⁺-(R₂OH) bond dissociation energies were also calculated using quantum chemical theory at the MP2(full)/6-311+G(2d,2p)// MP2(full)/6-31G(d) level (corrected for zero-point energies and basis set superposition errors) and are generally in good agreement with the experimentally determined values.