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Puzzarini C, Tasinato N, Bloino J, Spada L, Barone V. State-of-the-art computation of the rotational and IR spectra of the methyl-cyclopropyl cation: hints on its detection in space. Phys Chem Chem Phys 2019; 21:3431-3439. [PMID: 30110028 DOI: 10.1039/c8cp04629h] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Recent measurements by the Cassini Ion Neutral Mass Spectrometer demonstrated the presence of numerous carbocations in Titan's upper atmosphere. In [Ali et al., Planet. Space Sci., 2013, 87, 96], an analysis of these measurements revealed the formation of the three-membered cyclopropenyl cation and its methyl derivatives. As a starting point of a future coordinated effort of laboratory experiments, quantum-chemical calculations, and astronomical observations, in the present work the molecular structure and spectroscopic properties of the methyl-cyclopropenyl cation have been investigated by means of state-of-the-art computational approaches in order to simulate its rotational and infrared spectra. Rotational parameters have been predicted with an expected accuracy better than 0.1% for rotational constants and on the order of 1-2% for centrifugal-distortion terms. As for the infrared spectrum, despite the challenge of a large amplitude motion, fundamental transitions have been computed to a good accuracy, i.e., the uncertainties are expected to be smaller than 5-10 wavenumbers.
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Affiliation(s)
- Cristina Puzzarini
- Dipartimento di Chimica "Giacomo Ciamician", University of Bologna, via F. Selmi 2, I-40126 Bologna, Italy.
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Cernuto A, Lopes A, Romanzin C, Cunha de Miranda B, Ascenzi D, Tosi P, Tonachini G, Maranzana A, Polášek M, Žabka J, Alcaraz C. Effects of collision energy and vibrational excitation of CH 3+ cations on its reactivity with hydrocarbons: But-2-yne CH 3CCCH 3 as reagent partner. J Chem Phys 2017; 147:154302. [PMID: 29055295 DOI: 10.1063/1.4990514] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
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 H2 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.
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Affiliation(s)
- Andrea Cernuto
- Department of Physics, University of Trento, Via Sommarive 14, Trento I-38123, Italy
| | - Allan Lopes
- Laboratoire de Chimie Physique, Bât. 350, UMR 8000, CNRS-Univ. Paris-Sud 11 and Paris Saclay, Centre Universitaire Paris-Sud, 91405 Orsay Cedex, France
| | - Claire Romanzin
- Laboratoire de Chimie Physique, Bât. 350, UMR 8000, CNRS-Univ. Paris-Sud 11 and Paris Saclay, Centre Universitaire Paris-Sud, 91405 Orsay Cedex, France
| | | | - Daniela Ascenzi
- Department of Physics, University of Trento, Via Sommarive 14, Trento I-38123, Italy
| | - Paolo Tosi
- Department of Physics, University of Trento, Via Sommarive 14, Trento I-38123, Italy
| | - Glauco Tonachini
- Department of Chemistry, University of Torino, Via Pietro Giuria, 7, Torino I-10125, Italy
| | - Andrea Maranzana
- Department of Chemistry, University of Torino, Via Pietro Giuria, 7, Torino I-10125, Italy
| | - Miroslav Polášek
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3, 182 23 Prague 8, Czech Republic
| | - Jan Žabka
- J. Heyrovský Institute of Physical Chemistry of the Czech Academy of Sciences, Dolejškova 3, 182 23 Prague 8, Czech Republic
| | - Christian Alcaraz
- Laboratoire de Chimie Physique, Bât. 350, UMR 8000, CNRS-Univ. Paris-Sud 11 and Paris Saclay, Centre Universitaire Paris-Sud, 91405 Orsay Cedex, France
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Olkhov RV, Nizkorodov SA, Dopfer O. Intermolecular interaction in the CH3+–He ionic complex revealed by ab initio calculations and infrared photodissociation spectroscopy. J Chem Phys 1999. [DOI: 10.1063/1.478917] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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