RT Journal Article
T1 The N(<sup>2</sup>D) + CH<sub>2</sub>CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan
A1 Recio Ibáñez, Pedro
A1 Vanuzzo, Gianmarco
A1 Marchione, Demian
A1 Mancini, Luca
A1 Liang, Pengxiao
A1 Pannacci, Giacomo
A1 Tan, Yuxin
A1 Rosi, Marzio
A1 Skouteris, Dimitrios
A1 Casavecchia, Piergiorgio
A1 Balucani, Nadia
AB The reaction of electronically excited nitrogen atoms, N(2D), with vinyl cyanide, CH2CHCN, has been investigated under single-collision conditions by the crossed molecular beam (CMB) scattering method with mass spectrometric detection and time-of-flight (TOF) analysis at the collision energy, Ec, of 31.4 kJ/mol. Synergistic electronic structure calculations of the doublet potential energy surface (PES) have been performed to assist in the interpretation of the experimental results and characterize the overall reaction micromechanism. Statistical (Rice–Ramsperger–Kassel–Marcus, RRKM) calculations of product branching fractions (BFs) on the theoretical PES have been carried out at different values of temperature, including the one corresponding to the temperature (175 K) of Titan’s stratosphere and at a total energy corresponding to the Ec of the CMB experiment. According to our theoretical calculations, the reaction is found to proceed via barrierless addition of N(2D) to the carbon–carbon double bond of CH2═CH–CN, followed by the formation of cyclic and linear intermediates that can undergo H, CN, and HCN elimination. In competition, the N(2D) addition to the CN group is also possible via a submerged barrier, leading ultimately to N2 + C3H3 formation, the most exothermic of all possible channels. Product angular and TOF distributions have been recorded for the H-displacement channels leading to the formation of a variety of possible C3H2N2 isomeric products. Experimentally, no evidence of CN, HCN, and N2 forming channels was observed. These findings were corroborated by the theory, which predicts a variety of competing product channels, following N(2D) addition to the double bond, with the main ones, at Ec = 31.4 kJ/mol, being six isomeric H forming channels: c-CH(N)CHCN + H (BF = 35.0%), c-CHNCHCN + H (BF = 28.1%), CH2NCCN + H (BF = 26.3%), c-CH2(N)CCN(cyano-azirine) + H (BF = 7.4%), trans-HNCCHCN + H (BF = 1.6%), and cis-HNCCHCN + H (BF = 1.3%), while C–C bond breaking channels leading to c-CH2(N)CH(2H-azirine) + CN and c-CH2(N)C + HCN are predicted to be negligible (0.02% and 0.2%, respectively). The highly exothermic N2 + CH2CCH (propargyl) channel is also predicted to be negligible because of the very high isomerization barrier from the initial addition intermediate to the precursor intermediate able to lead to products. The predicted product BFs are found to have, in general, a very weak energy dependence. The above cyclic and linear products containing an additional C–N bond could be potential precursors of more complex, N-rich organic molecules that contribute to the formation of the aerosols on Titan’s upper atmosphere. Overall, the results are expected to have a significant impact on the gas-phase chemistry of Titan’s atmosphere and should be properly included in the photochemical models.
PB ACS Publications
SN 1089-5639
SN 1520-5215
YR 2022
FD 2022-09-02
LK https://hdl.handle.net/20.500.14352/131307
UL https://hdl.handle.net/20.500.14352/131307
LA eng
NO Gianmarco Vanuzzo, Demian Marchione, Luca Mancini, Pengxiao Liang, Giacomo Pannacci, Pedro Recio, Yuxin Tan, Marzio Rosi, Dimitrios Skouteris, Piergiorgio Casavecchia, and Nadia Balucani The Journal of Physical Chemistry A 2022 126 (36), 6110-6123 DOI: 10.1021/acs.jpca.2c04263
NO Copyright © 2022 The Authors. Published by American Chemical Society
NO Italian Space Agency
NO European Union’s Horizon 2020
NO “Dipartimento di Ingegneria Civile e Ambientale” of the University of Perugia
DS Docta Complutense
RD 8 abr 2026