| Abstract
| - Quantum chemical calculations are used to explore the proton-transfer reactivity of O-protonated vinyl alcohol,CH2CHOH2+, with phosphorus nitride, PN. This reaction is relevant to the chemical evolution of interstellarclouds, since O-protonated vinyl alcohol has been postulated (and tentatively identified) as a product of theassociation reaction between interstellar H3O+ and C2H2, while PN is the most widespread and abundantphosphorus-containing molecule seen in astrophysical environments. Furthermore, the reaction exhibits anunusual mechanistic feature, namely, an extended “proton-transport catalysis” mechanism, which wecharacterize here as a “proton-transfer triple play”. The reaction proceeds initially by proton transfer fromCH2CHOH2+ to PN, then from PNH+ to CH2CHOH, and finally from CH3CHOH+ to PN, where theemphasized atom indicates the resultant site of protonation/deprotonation. Thus, the ultimate overall bimolecularproton-transfer reaction is expected to occur as CH2CHOH2+ + PN → CH3CHO + PNH+; that is, the apparentfavored product channel exhibits not only proton transfer but also keto/enol tautomerization. The triple-playmechanism can be rationalized in terms of the proton affinities of vinyl alcohol, acetaldehyde, and phosphorusnitride, which here are satisfactorily reproduced by high-level ab initio calculations. Other neutrals with aproton affinity appropriate for the possible triple-play mechanism converting CH2CHOH2+ to CH3CHO arealso identified, with a view to encouraging experimental investigation of this mechanism.
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