1
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Balucani N, Vanuzzo G, Recio P, Caracciolo A, Rosi M, Cavallotti C, Baggioli A, Della Libera A, Casavecchia P. Crossed molecular beam experiments and theoretical simulations on the multichannel reaction of toluene with atomic oxygen. Faraday Discuss 2024; 251:523-549. [PMID: 38868901 DOI: 10.1039/d3fd00181d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2024]
Abstract
Despite extensive experimental and theoretical studies on the kinetics of the O(3P) + C7H8 (toluene) reaction and a pioneering crossed molecular beam (CMB) investigation, the branching fractions (BFs) of the CH3C6H4O(methylphenoxy) + H, C6H5O(phenoxy) + CH3, and spin-forbidden C5H5CH3 (methylcyclopentadiene) + CO product channels remain an open question, which has hampered the proper inclusion of this important reaction in the chemical modelling of various chemical environments. We report a CMB study with universal soft electron-ionization mass-spectrometric detection of the reactions O(3P,1D) + toluene at the collision energy of 34.7 kJ mol-1. From CMB data we have inferred the reaction dynamics and quantified the BFs of the primary products and the role of intersystem crossing (ISC). The CH3-elimination channel dominates (BF = 0.69 ± 0.22) in the O(3P) reaction, while the H-displacement and CO-formation channels are minor (BF = 0.22 ± 0.07 and 0.09 ± 0.05, respectively), with ISC accounting for more than 50% of the reactive flux. Synergistic transition-state theory (TST)-based master equation simulations including nonadiabatic TST on ab initio coupled triplet/singlet potential energy surfaces were employed to compute the product BFs and assist in the interpretation of the CMB results. In the light of the good agreement between the theoretical predictions for the O(3P) + toluene reaction and the CMB results as well as the absolute rate constant as a function of temperature (T) (from literature), the so-validated computational methodology was used to predict channel-specific rate constants as a function of T at 1 atm.
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Affiliation(s)
- Nadia Balucani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia 06123, Italy.
| | - Gianmarco Vanuzzo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia 06123, Italy.
| | - Pedro Recio
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia 06123, Italy.
| | - Adriana Caracciolo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia 06123, Italy.
| | - Marzio Rosi
- Dipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Perugia, Perugia 06125, Italy
| | - Carlo Cavallotti
- Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica, Milano 20131, Italy
| | - Alberto Baggioli
- Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica, Milano 20131, Italy
| | - Andrea Della Libera
- Politecnico di Milano, Dipartimento di Chimica, Materiali e Ingegneria Chimica, Milano 20131, Italy
| | - Piergiorgio Casavecchia
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia 06123, Italy.
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2
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Balucani N, Caracciolo A, Vanuzzo G, Skouteris D, Rosi M, Pacifici L, Casavecchia P, Hickson KM, Loison JC, Dobrijevic M. An experimental and theoretical investigation of the N( 2D) + C 6H 6 (benzene) reaction with implications for the photochemical models of Titan. Faraday Discuss 2023; 245:327-351. [PMID: 37293920 DOI: 10.1039/d3fd00057e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We report on a combined experimental and theoretical investigation of the N(2D) + C6H6 (benzene) reaction, which is of relevance in the aromatic chemistry of the atmosphere of Titan. Experimentally, the reaction was studied (i) under single-collision conditions by the crossed molecular beams (CMB) scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy (Ec) of 31.8 kJ mol-1 to determine the primary products, their branching fractions (BFs), and the reaction micromechanism, and (ii) in a continuous supersonic flow reactor to determine the rate constant as a function of temperature from 50 K to 296 K. Theoretically, electronic structure calculations of the doublet C6H6N potential energy surface (PES) were performed to assist the interpretation of the experimental results and characterize the overall reaction mechanism. The reaction is found to proceed via barrierless addition of N(2D) to the aromatic ring of C6H6, followed by formation of several cyclic (five-, six-, and seven-membered ring) and linear isomeric C6H6N intermediates that can undergo unimolecular decomposition to bimolecular products. Statistical estimates of product BFs on the theoretical PES were carried out under the conditions of the CMB experiments and at the temperatures relevant for Titan's atmosphere. In all conditions the ring-contraction channel leading to C5H5 (cyclopentadienyl) + HCN is dominant, while minor contributions come from the channels leading to o-C6H5N (o-N-cycloheptatriene radical) + H, C4H4N (pyrrolyl) + C2H2 (acetylene), C5H5CN (cyano-cyclopentadiene) + H, and p-C6H5N + H. Rate constants (which are close to the gas kinetic limit at all temperatures, with the recommended value of 2.19 ± 0.30 × 10-10 cm3 s-1 over the 50-296 K range) and BFs have been used in a photochemical model of Titan's atmosphere to simulate the effect of the title reaction on the species abundances as a function of the altitude.
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Affiliation(s)
- Nadia Balucani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.
| | - Adriana Caracciolo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.
| | - Gianmarco Vanuzzo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.
| | | | - Marzio Rosi
- Dipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Perugia, 06100, Perugia, Italy
| | - Leonardo Pacifici
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.
| | - Piergiorgio Casavecchia
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy.
| | - Kevin M Hickson
- Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255, F-33400 Talence, France
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Pannacci G, Mancini L, Vanuzzo G, Liang P, Marchione D, Rosi M, Casavecchia P, Balucani N. A combined crossed molecular beam and theorerical study of the O( 3P, 1D) + acrylonitrile (CH 2CHCN) reactions and implications for combustion and extraterrestrial environments. Phys Chem Chem Phys 2023. [PMID: 37469256 DOI: 10.1039/d3cp01558k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2023]
Abstract
Acrylonitrile (CH2CHCN) is ubiquitous in space (molecular clouds, solar-type star forming regions, and circumstellar envelopes) and is also abundant in the upper atmosphere of Titan. The reaction O(3P) + CH2CHCN can be of relevance in the chemistry of the interstellar medium because of the abundance of atomic oxygen. The oxidation of acrylonitrile is also important in combustion as the thermal decomposition of pyrrolic and pyridinic structures present in fuel-bound nitrogen generates many nitrogen-bearing compounds, including acrylonitrile. Despite its relevance, limited information exists on this reaction. We report a combined experimental and theoretical investigation of the reactions of acrylonitrile with both ground 3P and excited 1D atomic oxygen. From product angular and time-of-flight distributions in crossed molecular beam experiments with mass spectrometric detection at a collision energy, Ec, of 31.4 kJ mol-1, we have identified the primary reaction products and determined their branching fractions (BFs). Theoretical calculations of the relevant triplet and singlet potential energy surfaces (PESs) were performed to interpret the experimental results and elucidate the reaction mechanism. Adiabatic statistical calculations of product BFs for the decomposition of the main triplet and singlet intermediates have been carried out. Combining the experimental and theoretical results, we conclude that the O(3P) reaction leads to two main product channels: (i) CH2CNH (ketenimine) + CO (dominant with a BF of 0.87 ± 0.05), formed via efficient intersystem crossing from the entrance triplet PES to the underlying singlet PES, and (ii) HCOCHCN + H (minor, with a BF of 0.13 ± 0.05), occurring adiabatically on the triplet PES. Our study suggests the inclusion of this reaction as a possible destruction pathway of CH2CHCN and a possible formation route of CH2CNH in the interstellar medium. The O(1D) + CH2CHCN reaction mainly leads to the formation of CH2CNH + CO adiabatically on the singlet PES. This result can improve models related to the chemistry of interstellar ice and cometary comas, where O(1D) reactions can play a role. Overall, our results are expected to be useful for improving the models of combustion and extraterrestrial environments.
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Affiliation(s)
- Giacomo Pannacci
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy.
| | - Luca Mancini
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy.
| | - Gianmarco Vanuzzo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy.
| | - Pengxiao Liang
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy.
| | - Demian Marchione
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy.
| | - Marzio Rosi
- Dipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Perugia, Perugia, Italy
| | - Piergiorgio Casavecchia
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy.
| | - Nadia Balucani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Perugia, Italy.
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Liang P, de Aragão EVF, Giani L, Mancini L, Pannacci G, Marchione D, Vanuzzo G, Faginas-Lago N, Rosi M, Skouteris D, Casavecchia P, Balucani N. OH( 2Π) + C 2H 4 Reaction: A Combined Crossed Molecular Beam and Theoretical Study. J Phys Chem A 2023. [PMID: 37207281 DOI: 10.1021/acs.jpca.2c08662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
The reaction between the ground-state hydroxyl radical, OH(2Π), and ethylene, C2H4, has been investigated under single-collision conditions by the crossed molecular beam scattering technique with mass-spectrometric detection and time-of-flight analysis at the collision energy of 50.4 kJ/mol. Electronic structure calculations of the underlying potential energy surface (PES) and statistical Rice-Ramsperger-Kassel-Marcus (RRKM) calculations of product branching fractions on the derived PES for the addition pathway have been performed. The theoretical results indicate a temperature-dependent competition between the anti-/syn-CH2CHOH (vinyl alcohol) + H, CH3CHO (acetaldehyde) + H, and H2CO (formaldehyde) + CH3 product channels. The yield of the H-abstraction channel could not be quantified with the employed methods. The RRKM results predict that under our experimental conditions, the anti- and syn-CH2CHOH + H product channels account for 38% (in similar amounts) of the addition mechanism yield, the H2CO + CH3 channel for ∼58%, while the CH3CHO + H channel is formed in negligible amount (<4%). The implications for combustion and astrochemical environments are discussed.
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Affiliation(s)
- Pengxiao Liang
- Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia, Perugia 06123, Italy
| | - Emília Valença Ferreira de Aragão
- Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia, Perugia 06123, Italy
- Master-Tec Srl, Via Sicilia, 41, Perugia 06128, Italy
| | - Lisa Giani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia, Perugia 06123, Italy
- Université Grenoble Alpes, 621 Av. Centrale, Saint-Martin-d'Hères 38400, France
| | - Luca Mancini
- Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia, Perugia 06123, Italy
| | - Giacomo Pannacci
- Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia, Perugia 06123, Italy
| | - Demian Marchione
- Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia, Perugia 06123, Italy
| | - Gianmarco Vanuzzo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia, Perugia 06123, Italy
| | - Noelia Faginas-Lago
- Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia, Perugia 06123, Italy
- Master-Tec Srl, Via Sicilia, 41, Perugia 06128, Italy
| | - Marzio Rosi
- Dipartimento di Ingegneria Civile Ed Ambientale, Università Degli Studi di Perugia, Perugia 06125, Italy
| | | | - Piergiorgio Casavecchia
- Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia, Perugia 06123, Italy
| | - Nadia Balucani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia, Perugia 06123, Italy
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5
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Liang P, de Aragão EVF, Pannacci G, Vanuzzo G, Giustini A, Marchione D, Recio P, Ferlin F, Stranges D, Lago NF, Rosi M, Casavecchia P, Balucani N. Reactions O( 3P, 1D) + HCCCN(X 1Σ +) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments. J Phys Chem A 2023; 127:685-703. [PMID: 36638186 PMCID: PMC9884085 DOI: 10.1021/acs.jpca.2c07708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Cyanoacetylene (HCCCN), the first member of the cyanopolyyne family (HCnN, where n = 3, 5, 7, ...), is of particular interest in astrochemistry being ubiquitous in space (molecular clouds, solar-type protostars, protoplanetary disks, circumstellar envelopes, and external galaxies) and also relatively abundant. It is also abundant in the upper atmosphere of Titan and comets. Since oxygen is the third most abundant element in space, after hydrogen and helium, the reaction O + HCCCN can be of relevance in the chemistry of extraterrestrial environments. Despite that, scarce information exists not only on the reactions of oxygen atoms with cyanoacetylene but with nitriles in general. Here, we report on a combined experimental and theoretical investigation of the reactions of cyanoacetylene with both ground 3P and excited 1D atomic oxygen and provide detailed information on the primary reaction products, their branching fractions (BFs), and the overall reaction mechanisms. More specifically, the reactions of O(3P, 1D) with HCCCN(X1Σ+) have been investigated under single-collision conditions by the crossed molecular beams scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy, Ec, of 31.1 kJ/mol. From product angular and time-of-flight distributions, we have identified the primary reaction products and determined their branching fractions (BFs). Theoretical calculations of the relevant triplet and singlet potential energy surfaces (PESs) were performed to assist the interpretation of the experimental results and clarify the reaction mechanism. Adiabatic statistical calculations of product BFs for the decomposition of the main triplet and singlet intermediates have also been carried out. Merging together the experimental and theoretical results, we conclude that the O(3P) reaction is characterized by a minor adiabatic channel leading to OCCCN (cyanoketyl) + H (experimental BF = 0.10 ± 0.05), while the dominant channel (BF = 0.90 ± 0.05) occurs via intersystem crossing to the underlying singlet PES and leads to formation of 1HCCN (cyanomethylene) + CO. The O(1D) reaction is characterized by the same two channels, with the relative CO/H yield being slightly larger. Considering the recorded reactive signal and the calculated entrance barrier, we estimate that the rate coefficient for reaction O(3P) + HC3N at 300 K is in the 10-12 cm3 molec-1 s-1 range. Our results are expected to be useful to improve astrochemical and photochemical models. In addition, they are also relevant in combustion chemistry, because the thermal decomposition of pyrrolic and pyridinic structures present in fuel-bound nitrogen generates many nitrogen-bearing compounds, including cyanoacetylene.
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Affiliation(s)
- Pengxiao Liang
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy
| | - Emilia V. F. de Aragão
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy,Master-Tec
srl, Via Sicilia 41, Perugia 06128, Italy
| | - Giacomo Pannacci
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy
| | - Gianmarco Vanuzzo
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy
| | - Andrea Giustini
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy
| | - Demian Marchione
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy
| | - Pedro Recio
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy
| | - Francesco Ferlin
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy
| | - Domenico Stranges
- Dipartimento
di Chimica, Università degli Studi
La Sapienza, Roma 00185, Italy
| | - Noelia Faginas Lago
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy
| | - Marzio Rosi
- Dipartimento
di Ingegneria Civile e Ambientale, Università
degli Studi di Perugia, Perugia 06123, Italy
| | - Piergiorgio Casavecchia
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy,E-mail:
| | - Nadia Balucani
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, Perugia 06123, Italy,E-mail:
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6
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Vanuzzo G, Mancini L, Pannacci G, Liang P, Marchione D, Recio P, Tan Y, Rosi M, Skouteris D, Casavecchia P, Balucani N, Hickson KM, Loison JC, Dobrijevic M. Reaction N( 2D) + CH 2CCH 2 (Allene): An Experimental and Theoretical Investigation and Implications for the Photochemical Models of Titan. ACS EARTH & SPACE CHEMISTRY 2022; 6:2305-2321. [PMID: 36303717 PMCID: PMC9589905 DOI: 10.1021/acsearthspacechem.2c00183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 09/08/2022] [Accepted: 09/09/2022] [Indexed: 06/16/2023]
Abstract
We report on a combined experimental and theoretical investigation of the N(2D) + CH2CCH2 (allene) reaction of relevance in the atmospheric chemistry of Titan. Experimentally, the reaction was investigated (i) under single-collision conditions by the crossed molecular beams (CMB) scattering method with mass spectrometric detection and time-of-flight analysis at the collision energy (E c) of 33 kJ/mol to determine the primary products and the reaction micromechanism and (ii) in a continuous supersonic flow reactor to determine the rate constant as a function of temperature from 50 to 296 K. Theoretically, electronic structure calculations of the doublet C3H4N potential energy surface (PES) were performed to assist the interpretation of the experimental results and characterize the overall reaction mechanism. The reaction is found to proceed via barrierless addition of N(2D) to one of the two equivalent carbon-carbon double bonds of CH2CCH2, followed by the formation of several cyclic and linear isomeric C3H4N intermediates that can undergo unimolecular decomposition to bimolecular products with elimination of H, CH3, HCN, HNC, and CN. The kinetic experiments confirm the barrierless nature of the reaction through the measurement of rate constants close to the gas-kinetic rate at all temperatures. Statistical estimates of product branching fractions (BFs) on the theoretical PES were carried out under the conditions of the CMB experiments at room temperature and at temperatures (94 and 175 K) relevant for Titan. Up to 14 competing product channels were statistically predicted with the main ones at E c = 33 kJ/mol being formation of cyclic-CH2C(N)CH + H (BF = 87.0%) followed by CHCCHNH + H (BF = 10.5%) and CH2CCNH + H (BF = 1.4%) the other 11 possible channels being negligible (BFs ranging from 0 to 0.5%). BFs under the other conditions are essentially unchanged. Experimental dynamical information could only be obtained on the overall H-displacement channel, while other possible channels could not be confirmed within the sensitivity of the method. This is also in line with theoretical predictions as the other possible channels are predicted to be negligible, including the HCN/HNC + C2H3 (vinyl) channels (overall BF < 1%). The dynamics and product distributions are dramatically different with respect to those observed in the isomeric reaction N(2D) + CH3CCH (propyne), where at a similar E c the main product channels are CH2NH (methanimine) + C2H (BF = 41%), c-C(N)CH + CH3 (BF = 32%), and CH2CHCN (vinyl cyanide) + H (BF = 12%). Rate coefficients (the recommended value is 1.7 (±0.2) × 10-10 cm3 s-1 over the 50-300 K range) and BFs have been used in a photochemical model of Titan's atmosphere to simulate the effect of the title reaction on the species abundance (including any new products formed) as a function of the altitude.
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Affiliation(s)
- Gianmarco Vanuzzo
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, 06123 Perugia, Italy
| | - Luca Mancini
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, 06123 Perugia, Italy
| | - Giacomo Pannacci
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, 06123 Perugia, Italy
| | - Pengxiao Liang
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, 06123 Perugia, Italy
| | - Demian Marchione
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, 06123 Perugia, Italy
| | - Pedro Recio
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, 06123 Perugia, Italy
| | - Yuxin Tan
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, 06123 Perugia, Italy
| | - Marzio Rosi
- Dipartimento
di Ingegneria Civile e Ambientale, Università
degli Studi di Perugia, 06100 Perugia, Italy
| | | | - Piergiorgio Casavecchia
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, 06123 Perugia, Italy
| | - Nadia Balucani
- Dipartimento
di Chimica, Biologia e Biotecnologie, Università
degli Studi di Perugia, 06123 Perugia, Italy
| | - Kevin M. Hickson
- Université
de Bordeaux, Institut des Sciences Moléculaires,
UMR 5255, F-33400 Talence, France
- CNRS,
Institut des Sciences Moléculaires, UMR 5255, F-33400 Talence, France
| | - Jean-Christophe Loison
- Université
de Bordeaux, Institut des Sciences Moléculaires,
UMR 5255, F-33400 Talence, France
- CNRS,
Institut des Sciences Moléculaires, UMR 5255, F-33400 Talence, France
| | - Michel Dobrijevic
- Laboratoire
d’Astrophysique de Bordeaux, Université
de Bordeaux, CNRS, B18N,
allée Geoffroy Saint-Hilaire, F-33615 Pessac, France
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7
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Vanuzzo G, Marchione D, Mancini L, Liang P, Pannacci G, Recio P, Tan Y, Rosi M, Skouteris D, Casavecchia P, Balucani N. The N( 2D) + CH 2CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan. J Phys Chem A 2022; 126:6110-6123. [PMID: 36053010 PMCID: PMC9483977 DOI: 10.1021/acs.jpca.2c04263] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
![]()
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.
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Affiliation(s)
- Gianmarco Vanuzzo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Demian Marchione
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Luca Mancini
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Pengxiao Liang
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Giacomo Pannacci
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Pedro Recio
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Yuxin Tan
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Marzio Rosi
- Dipartimento di Ingegneria Civile e Ambientale, Università degli Studi di Perugia, 06125 Perugia, Italy
| | | | - Piergiorgio Casavecchia
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Nadia Balucani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
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8
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Cavallotti C, Della Libera A, Zhou CW, Recio P, Caracciolo A, Balucani N, Casavecchia P. Crossed-beam and theoretical studies of multichannel nonadiabatic reactions: branching fractions and role of intersystem crossing for O(3P)+1,3-butadiene. Faraday Discuss 2022; 238:161-182. [DOI: 10.1039/d2fd00037g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Atomic oxygen reactions can contribute significantly to the oxidation of unsaturated aliphatic and aromatic hydrocarbons. The reaction mechanism is started by electrophilic O atom addition to the unsaturated bond(s) to...
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9
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Ramasesha K, Savee JD, Zádor J, Osborn DL. A New Pathway for Intersystem Crossing: Unexpected Products in the O( 3P) + Cyclopentene Reaction. J Phys Chem A 2021; 125:9785-9801. [PMID: 34730957 DOI: 10.1021/acs.jpca.1c05817] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We investigated the reaction of O(3P) with cyclopentene at 4 Torr and 298 K using time-resolved multiplexed photoionization mass spectrometry, where O(3P) radicals were generated by 351 nm photolysis of NO2 and reacted with excess cyclopentene in He under pseudo-first-order conditions. The resulting products were sampled, ionized, and detected by tunable synchrotron vacuum ultraviolet radiation and an orthogonal acceleration time-of-flight mass spectrometer. This technique enabled measurement of both mass spectra and photoionization spectra as functions of time following the initiation of the reaction. We observe propylketene (41%), acrolein + ethene (37%), 1-butene + CO (19%), and cyclopentene oxide (3%), of which the propylketene pathway was previously unidentified experimentally and theoretically. The automatically explored reactive potential energy landscape at the CCSD(T)-F12a/cc-pVTZ//ωB97X-D/6-311++G(d,p) level and the related master equation calculations predict that cyclopentene oxide is formed on the singlet potential energy surface, whereas propylketene is first formed on the triplet surface. These calculations provide evidence that significant intersystem crossing can happen in this reaction not only around the geometry of the initial triplet adduct but also around that of triplet propylketene. The formation of 1-butene + CO is initiated on the triplet surface, with bond cleavage and hydrogen transfer occurring during intersystem crossing to the singlet surface. At present, we are unable to explain the mechanistic origins of the acrolein + ethene channel, and we thus refrain from assigning singlet or triplet reactivity to this channel. Overall, at least 60% of the products result from triplet reactivity. We propose that the reactivity of cyclic alkenes with O(3P) is influenced by their greater effective degree of unsaturation compared with acyclic alkenes. This work also suggests that searches for minimum-energy crossing points that connect triplet surfaces to singlet surfaces should extend beyond the initial adducts.
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Affiliation(s)
- Krupa Ramasesha
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551-0969, United States
| | - John D Savee
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551-0969, United States
| | - Judit Zádor
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551-0969, United States
| | - David L Osborn
- Combustion Research Facility, Mail Stop 9055, Sandia National Laboratories, Livermore, California 94551-0969, United States.,Department of Chemical Engineering, University of California, Davis, California 95616, United States
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10
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Vanuzzo G, Caracciolo A, Minton TK, Balucani N, Casavecchia P, de Falco C, Baggioli A, Cavallotti C. Crossed-Beam and Theoretical Studies of the O( 3P, 1D) + Benzene Reactions: Primary Products, Branching Fractions, and Role of Intersystem Crossing. J Phys Chem A 2021; 125:8434-8453. [PMID: 34533308 PMCID: PMC8488941 DOI: 10.1021/acs.jpca.1c06913] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Reliable modeling
of hydrocarbon oxidation relies critically on
knowledge of the branching fractions (BFs) as a function of temperature
(T) and pressure (p) for the products
of the reaction of the hydrocarbon with atomic oxygen in its ground
state, O(3P). During the past decade, we have performed
in-depth investigations of the reactions of O(3P) with
a variety of small unsaturated hydrocarbons using the crossed molecular
beam (CMB) technique with universal mass spectrometric
(MS) detection and time-of-flight (TOF) analysis, combined with synergistic
theoretical calculations of the relevant potential energy surfaces
(PESs) and statistical computations of product BFs, including intersystem
crossing (ISC). This has allowed us to determine the primary products,
their BFs, and extent of ISC to ultimately provide theoretical channel-specific
rate constants as a function of T and p. In this work, we have extended this approach to the oxidation of
one of the most important species involved in the combustion of aromatics:
the benzene (C6H6) molecule. Despite extensive
experimental and theoretical studies on the kinetics and dynamics
of the O(3P) + C6H6 reaction, the
relative importance of the C6H5O (phenoxy) +
H open-shell products and of the spin-forbidden C5H6 (cyclopentadiene) + CO and phenol adduct closed-shell products
are still open issues, which have hampered the development of reliable
benzene combustion models. With the CMB technique, we have investigated
the reaction dynamics of O(3P) + benzene at a collision
energy (Ec) of 8.2 kcal/mol, focusing
on the occurrence of the phenoxy + H and spin-forbidden C5H6 + CO and phenol channels in order to shed further light
on the dynamics of this complex and important reaction, including
the role of ISC. Concurrently, we have also investigated the reaction
dynamics of O(1D) + benzene at the same Ec. Synergistic high-level electronic structure calculations
of the underlying triplet/singlet PESs, including nonadiabatic couplings,
have been performed to complement and assist the interpretation of
the experimental results. Statistical (RRKM)/master equation (ME)
computations of the product distribution and BFs on these PESs, with
inclusion of ISC, have been performed and compared to experiment.
In light of the reasonable agreement between the CMB experiment, literature
kinetic experimental results, and theoretical predictions for the
O(3P) + benzene reaction, the so-validated computational
methodology has been used to predict (i) the BF between the C6H5O + H and C5H6 + CO channels
as a function of collision energy and temperature (at 0.1 and 1 bar),
showing that their increase progressively favors radical (phenoxy
+ H)-forming over molecule (C5H6 + CO and phenol
stabilization)-forming channels, and (ii) channel-specific rate constants
as a function of T and p, which
are expected to be useful for improved combustion models.
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Affiliation(s)
- Gianmarco Vanuzzo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Adriana Caracciolo
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Timothy K Minton
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Nadia Balucani
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Piergiorgio Casavecchia
- Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Carlo de Falco
- MOX - Modellistica e Calcolo Scientifico, Dipartimento di Matematica, Politecnico di Milano, 20133 Milano, Italy
| | - Alberto Baggioli
- Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, 20131 Milano, Italy
| | - Carlo Cavallotti
- Dipartimento di Chimica, Materiali e Ingegneria Chimica, Politecnico di Milano, 20131 Milano, Italy
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11
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Caracciolo A, Vanuzzo G, Balucani N, Stranges D, Casavecchia P, Pratali Maffei L, Cavallotti C. Combined Experimental and Theoretical Studies of the O(3P) + 1-Butene Reaction Dynamics: Primary Products, Branching Fractions, and Role of Intersystem Crossing. J Phys Chem A 2019; 123:9934-9956. [DOI: 10.1021/acs.jpca.9b07621] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Adriana Caracciolo
- Laboratory of Molecular Processes in Combustion, Department of Chemistry, Biology and Biotechnologies, University of Perugia, 06123 Perugia, Italy
| | - Gianmarco Vanuzzo
- Laboratory of Molecular Processes in Combustion, Department of Chemistry, Biology and Biotechnologies, University of Perugia, 06123 Perugia, Italy
| | - Nadia Balucani
- Laboratory of Molecular Processes in Combustion, Department of Chemistry, Biology and Biotechnologies, University of Perugia, 06123 Perugia, Italy
| | - Domenico Stranges
- Laboratory of Molecular Processes in Combustion, Department of Chemistry, Biology and Biotechnologies, University of Perugia, 06123 Perugia, Italy
| | - Piergiorgio Casavecchia
- Laboratory of Molecular Processes in Combustion, Department of Chemistry, Biology and Biotechnologies, University of Perugia, 06123 Perugia, Italy
| | - Luna Pratali Maffei
- Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta”, Politecnico di Milano, 20131 Milano, Italy
| | - Carlo Cavallotti
- Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta”, Politecnico di Milano, 20131 Milano, Italy
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