Effects of collision energy and vibrational excitation of CH3+ cations on its reactivity with hydrocarbons: But-2-yne CH3CCCH3 as reagent partner

0482743 - ÚFCH JH 2018 RIV US eng J - Článek v odborném periodiku
Cernuto, A. - Lopes, A. - Romanzin, C. - de Miranda, B. C. - Ascenzi, D. - Tosi, P. - Tonachini, G. - Maranzana, A. - Polášek, Miroslav - Žabka, Ján - Alcaraz, Ch.
Effects of collision energy and vibrational excitation of CH3+ cations on its reactivity with hydrocarbons: But-2-yne CH3CCCH3 as reagent partner.
Journal of Chemical Physics. Roč. 147, č. 15 (2017), č. článku 154302. ISSN 0021-9606. E-ISSN 1089-7690
Grant CEP: GA MŠMT(CZ) LD14024; GA ČR(CZ) GA17-14200S
Grant ostatní: COST(XE) TD1308; COST(XE) CM1401
Institucionální podpora: RVO:61388955
Klíčová slova: titans upper-atmosphere * dielectric barrier discharge * main-group thermochemistry * ion-molecule reactions * basis-set convergence
Obor OECD: Physical chemistry
Impakt faktor: 2.843, rok: 2017

The methyl carbocation is ubiquitous in gaseous environments, such as planetary ionospheres, cometary comae, and the interstellar medium, as well as combustion systems and plasma setups for technological applications. Here we report on a joint experimental and theoretical study on the mechanism of the reaction CH3+ + CH3CCCH3 (but-2-yne, also known as dimethylacetylene), by combining guided ion beam mass spectrometry experiments with ab initio calculations of the potential energy hypersurface. Such a reaction is relevant in understanding the chemical evolution of Saturn's largest satellite, Titan. Two complementary setups have been used: in one case, methyl cations are generated via electron ionization, while in the other case, direct vacuum ultraviolet photoionization with synchrotron radiation of methyl radicals is used to study internal energy effects on the reactivity. Absolute reactive cross sections have been measured as a function of collision energy, and product branching ratios have been derived. The two most abundant products result from electron and hydride transfer, occurring via direct and barrierless mechanisms, while other channels are initiated by the electrophilic addition of the methyl cation to the triple bond of but-2-yne. Among the minor channels, special relevance is placed on the formation of C5H7+, stemming from H-2 loss from the addition complex. This is the only observed condensation product with the formation of new C-C bonds, and it might represent a viable pathway for the synthesis of complex organic species in astronomical environments and laboratory plasmas. Published by AIP Publishing.
Trvalý link: http://hdl.handle.net/11104/0278130