Some Ion–Molecule Reactions of H3+ and the Proton Affinity of H2

Abstract

The flowing afterglow technique has been used to study the reactions of H3+ with a number of neutral reactants at thermal energies. Proton transfer was the only primary reaction observed with N2, CO, CO2, N2O, NO, CH4, C2H2, H2O, and NH3. Both proton transfer and dissociative charge transfer were observed with C2H4 and C2H6, while dissociative charge transfer is the exclusive primary process with NO2. Secondary reactions were observed with NO, C2H6, C2H4, and C2H2. Cluster ions were formed between NO+ and NO2 and H2O, between H3O+ and H2O, CO2, and CO, and between NH4+ and NH3 and H2O. Proton transfer was also observed between HN2+ and CO2, N2O, CH4, and H2O, and between HO2+ and H2 and N2. Rate constants were obtained for these reactions and are discussed. Limits could be placed on the proton affinity (P.A.) of H2 from the failure to observe rapid proton transfer to O2 and the observation of proton transfer to N2. These indicate 4.2 < P.A. (H2)< 4.7 eV with a recommended value of 4.4 eV. The technique can be used to measure relative proton affinities of gases.

Temperature Dependence of Two Key Interstellar Reactions of H3+: O(3P) + H3+ and CO + H3+

“…15,[51][52][53][54][55][56][57] The theoretical prediction is in reasonable agreement with the room temperature experimental measurements, being at the upper end of the error bars for most of the more precise measurements. However, it is hard to understand the discrepancy with the one low temperature measurement of Rowe and co-workers.…”

The Carbon Dioxide Molecule and the Effects of Its Interaction with Electrophiles and Nucleophiles

“…The proton affinity of the molecule ranges around 540.5 AE 2 kJ/mol [120], which is appreciably lower than those found for other O-containing molecules, such as H 2 [123,124]. Experimental data allow to distinguish between two possible structures: a cis conformation with a quasi-linear heavy-atom chain or a trans conformation with a small bending at the C atom [125].…”

Proton transfer chains in cold plasmas of H2with small amounts of N2. The prevalence of NH4+

“…acts as an effective proton donor for many of the species likely to be found in the ISM. 5,8,20 These "primordial" species are small molecules or radicals containing oxygen, carbon, and nitrogen, which are, after hydrogen and He, the most abundant atoms.…”