1. Mechanisms of sequential ion-molecule reactions in protonated methanol using mass spectrometry, ab initio methods, and statistical modeling
- Author
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Rachel E. Mizrahi, Jennifer E. Ruliffson, Melanie C. White, Matthew Khoury, and Joshua J. Melko
- Subjects
Reaction mechanism ,010304 chemical physics ,Dimer ,Ab initio ,Solvation ,General Physics and Astronomy ,Protonation ,010402 general chemistry ,Mass spectrometry ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Computational chemistry ,0103 physical sciences ,Mass spectrum ,Molecule ,Physical and Theoretical Chemistry ,Nuclear Experiment ,Astrophysics::Galaxy Astrophysics - Abstract
We present mass spectrometry results for reactions of protonated methanol clusters, (CH3OH)nH+. Mass spectra indicate a preference for association over condensation at our experimental conditions and are used in conjunction with computational methods to probe the reaction mechanisms involved. We find that the reaction for the protonated monomer with neutral methanol consists of two entrance complexes that are in equilibrium due to a very small barrier between them. Statistical modeling indicates that competition between proton transfer, condensation, and association are dictated by the depth of the proton-bound complex and the height of the SN2 transition state. For the reaction of the protonated dimer we determine condensation is not energetically favorable at thermal energies as a solvation effect raises the SN2 barrier. Geometries for protonated methanol clusters (CH3OH)nH+ up to n = 6 are also provided, which allow us to examine the role of entropy and hydrogen bonding in these structures.
- Published
- 2019
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