The dissociation dynamics of energy-selected neopentylamine ions: Heats of formation of neopentylamine and neopentyl alcohol

The dissociation dynamics of energy-selected neopentylamine cations, (CH3)3CCH2NH2+, were studied using threshold photoelectron photoion coincidence (TPEPICO) spectroscopy in which ion time-of-flight (TOF) distributions are recorded as a function of the ion internal energy. The lowest energy pathway, producing the CH3NH3+ ion, involves a rearrangement of the molecular ion. The 0 K dissociation onsets for the production of the CH3NH3+, CH2NH2+, and (CH3)2CCH2NH2+ ions have been determined to be 9.54 ± 0.05, 9.647 ± 0.025 and 9.90 ± 0.1 eV, respectively. Because the heat of formation of the CH2NH2+ + t-C4H9 products are established, we can use the measured onset of 9.647 eV for this reaction to establish the neopentylamine ΔfH298°=−130.3±3.3 kJ/mol. This result is used in a group additivity scheme to estimate the neopentyl alcohol heat of formation as ΔfH298°=−315.5±4 kJ mol−1. Both of these results are strongly supported by a series of isodesmic reactions calculated at the G3B3 and CBS-APNO levels. This is the first reported experimental heat of formation of the neopentylamine and the first reported heat of formation of the neopentyl alcohol.