Kinetic mass spectrometric investigation of the reactions of t-C4H9+ ions with some simple polar molecules at thermal energies

The interactions of $t\text{-}{C}_4{H}_9^{+}$ ions from neopentane with some simple polar molecules have been investigated in a high pressure photoionization mass spectrometer at thermal kinetic energies. Proton transfer was found to occur from $t\text{-}{C}_4{H}_9^{+}$ to acetone, ammonia, and the various methylamines, but not to molecules having estimated proton affinities < 195 kcal/mol (815 kJ/mol). Macroscopic thermal rate coefficients are reported for the various proton transfer reactions, all of which are on the order of 10⁻⁹ cm³/molecule · second. The reaction $t{\text{-C}}_4{\text{H}}_9^{+}+2{\text{CH}}_3\text{OH}\to {\left({\text{CH}}_3\text{OH}\right)}_2{\text{H}}^{+}+{\text{C}}_4{\text{H}}_8$ was found to occur, but not the analogous reaction with H₂O. On the basis of supplementary experiments, new limits are reported for the proton affinity of acetone. These are 203±2 kcal/mol < proton affinity of acetone < 207 kcal/mol.