Absolute binding energies of lithium ions to short chain alcohols, CnH2n+O-2, n=1-4, determined by threshold collision-induced dissociation

Collision-induced dissociation of Li+(ROH) with xenon is studied using guided ion beam mass spectrometry. ROH includes the following eight short chain alcohols: methanol, ethanol, 1-propanol, 2-propanol, l-butanol, 2-methyl-1-propanol, 2-butanol, and 2-methyl-2-propanol. In all cases, the primary product is endothermic loss of the neutral alcohol, with minor products that include those formed by ligand exchange, alkene and water loss, and C-C bond cleavage. The cross-section thresholds are interpreted to yield 0, 298, and 373 K bond energies for Li+-ROH after accounting for the effects of multiple ion-molecule collisions, internal energy of the reactant ions, and dissociation lifetimes. The experimental bond energies determined here show a fairly constant deviation from previous experimental measurements (as obtained by equilibrium studies in an ion cyclotron resonance mass spectrometer). This discrepancy is discussed in some detail because it affects the absolute Li+ affinity scale used extensively in the literature.