A Computational Study on the Insertion of N(2D) into a C—H or C—C Bond: The Reactions of N(2D) with Benzene and Toluene and Their Implications on the Chemistry of Titan

Rosi, Marzio; Pacifici, Leonardo; Skouteris, Dimitrios; Caracciolo, Adriana; Casavecchia, Piergiorgio; Falcinelli, Stefano; Balucani, Nadia

doi:10.1007/978-3-030-58808-3_54

Cited by 8 publications

(3 citation statements)

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“…Our experimental results have been accompanied by electronic structure calculations of the underlying potential energy surface (PES), and RRKM (Rice–Ramsperger–Kassel–Marcus) estimates of the product branching fractions (BFs) have been carried out under the conditions of our experiments and at the temperatures of relevance for Titan. The reactions N( 2 D) + CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , and C 3 H 4 isomers (methylacetylene and allene (unpublished results)) − as well as N( 2 D) + small aromatic compounds (pyridine, benzene, and toluene) − have been investigated. In a few cases, that is, for the N( 2 D) reactions with H 2 and H 2 O, more sophisticated dynamical calculations have been performed and the detailed reaction mechanism elucidated. − …”

Section: Introductionmentioning

confidence: 99%

The N(²D) + CH₂CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan

et al. 2022

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The reaction of electronically excited nitrogen atoms, N( 2 D), with vinyl cyanide, CH 2 CHCN, 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, E c , 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 E c of the CMB experiment. According to our theoretical calculations, the reaction is found to proceed via barrierless addition of N( 2 D) to the carbon–carbon double bond of CH 2 =CH–CN, followed by the formation of cyclic and linear intermediates that can undergo H, CN, and HCN elimination. In competition, the N( 2 D) addition to the CN group is also possible via a submerged barrier, leading ultimately to N 2 + C 3 H 3 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 C 3 H 2 N 2 isomeric products. Experimentally, no evidence of CN, HCN, and N 2 forming channels was observed. These findings were corroborated by the theory, which predicts a variety of competing product channels, following N( 2 D) addition to the double bond, with the main ones, at E c = 31.4 kJ/mol, being six isomeric H forming channels: c -CH(N)CHCN + H (BF = 35.0%), c -CHNCHCN + H (BF = 28.1%), CH 2 NCCN + H (BF = 26.3%), c -CH 2 (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 -CH 2 (N)CH(2H-azirine) + CN and c -CH 2 (N)C + HCN are predicted to be negligible (0.02% and 0.2%, respectively). The highly exothermic N 2 + CH 2 CCH (propargyl) channel is also predicted to be negligible because of the very high isomerization barrier from the initial addition intermedia...

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Section: Introductionmentioning

confidence: 99%

The N(²D) + CH₂CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan

et al. 2022

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“…CMB results have always been complemented by electronic structure calculations of the relevant stationary points of the underlying potential energy surface (PES) and statistical (Rice-Ramsperger-Kassel-Marcus) calculations of the branching fractions. This combined theoretical and experimental approach was applied to the multichannel reactions N( 2 D) + CH 4 , C 2 H 2 , C 2 H 4 , and C 2 H 6 . − Much more recently, within the framework of the Italian National Project of Astrobiology, we conducted a combined experimental and theoretical investigation of the reaction of N( 2 D) with HCCCN (cyanoacetylene), C 5 H 5 N (pyridine), allene (unpublished results), C 6 H 6 (benzene), − and C 6 H 5 CH 3 (toluene) . In all cases, new species holding a novel C–N bond were identified as major reaction products, thus implying that N( 2 D) reactions with hydrocarbons are major players in the initiation of nitrile chemistry.…”

Section: Introductionmentioning

confidence: 99%

The Reaction N(²D) + CH₃CCH (Methylacetylene): A Combined Crossed Molecular Beams and Theoretical Investigation and Implications for the Atmosphere of Titan

et al. 2021

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The reaction of excited nitrogen atoms N( 2 D) with CH 3 CCH (methylacetylene) was investigated 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 31.0 kJ/mol. Synergistic electronic structure calculations of the doublet potential energy surface (PES) were performed to assist the interpretation of the experimental results and characterize the overall reaction micromechanism. Theoretically, the reaction is found to proceed via a barrierless addition of N( 2 D) to the carbon–carbon triple bond of CH 3 CCH and an insertion of N( 2 D) into the CH bond of the methyl group, followed by the formation of cyclic and linear intermediates that can undergo H, CH 3 , and C 2 H elimination or isomerize to other intermediates before unimolecularly decaying to a variety of products. Kinetic calculations for addition and insertion mechanisms and statistical (Rice-Ramsperger-Kassel-Marcus) computations of product branching fractions (BFs) on the theoretical PES were performed at different values of total energy, including the one corresponding to the temperature (175 K) of Titan’s stratosphere and that of the CMB experiment. Up to 14 competing product channels were statistically predicted, with the main ones, at E c = 31.0 kJ/mol, being the formation of CH 2 NH (methanimine) + C 2 H (ethylidyne) (BF = 0.41), c -C(N)CH + CH 3 (BF = 0.32), CH 2 CHCN (acrylonitrile) + H (BF = 0.12), and c -CH 2 C(N)CH + H (BF = 0.04). Of the 14 possible channels, seven correspond to H displacement channels of different exothermicity, for a total H channel BF of ∼0.25 at E c = 31.0 kJ/mol. Experimentally, dynamical information could only be obtained about the overall H channels. In particular, the experiment corroborates the formation of acrylonitrile + H, which is the most exothermic of all 14 reaction channels and is theoretically calculated to be the dominant H-forming channel (BF = 0.12). The products containing a novel C–N bond could be potential precursors to form other nitriles (C 2 N 2 , C 3 N) or more complex organic species containing N atoms in planetary atmospheres, such as those of Titan and Pluto. Overall, the results are expected to have a potentially significant impact on the understanding of the gas-phase chemistry of Titan’s atmosphere and the modeling of that atmosphere.

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“…Zhang et al suggested that a reactive H 2 ONO + species is formed in the low-temperature plasma, which leads to the type of aromatic substitution followed by ring opening and closing, with further investigation recommended . Recent reports suggest that excited-state nitrogen, N( 2 D), may react with benzene and toluene to form pyridine and methylpyridine, respectively, − and is supported by earlier reports that reactions of active nitrogen with benzene lead to small yields of isocyanide, benzonitrile, and pyridine. , …”

Section: Introductionmentioning

confidence: 87%

Excited-State N Atoms Transform Aromatic Hydrocarbons into N-Heterocycles in Low-Temperature Plasmas

et al. 2022

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The direct formation of N-heterocycles from aromatic hydrocarbons has been observed in nitrogen-based lowtemperature plasmas; the mechanism of this unusual nitrogenfixation reaction is the topic of this paper. We used homologous aromatic compounds to study their reaction with reactive nitrogen species (RNS) in a dielectric barrier discharge ionization (DBDI) source. Toluene (C 7 H 8 ) served as a model compound to study the reaction in detail, which leads to the formation of two major products at "high" plasma voltage: a nitrogen-replacement product yielding protonated methylpyridine (C 6 H 8 N + ) and a protonated nitrogen-addition (C 7 H 8 N + ) product. We complemented those studies by a series of experiments probing the potential mechanism. Using a series of selected-ion flow tube experiments, we found that N + , N 2 + , and N 4 + react with toluene to form a small abundance of the N-addition product, while N( 4 S) reacted with toluene cations to form a fragment ion. We created a model for the RNS in the plasma using variable electron and neutral density attachment mass spectrometry in a flowing afterglow Langmuir probe apparatus. These experiments suggested that excited-state nitrogen atoms could be responsible for the N-replacement product. Density functional theory calculations confirmed that the reaction of excitedstate nitrogen N( 2 P) and N( 2 D) with toluene ions can directly form protonated methylpyridine, ejecting a carbon atom from the aromatic ring. N( 2 P) is responsible for this reaction in our DBDI source as it has a sufficient lifetime in the plasma and was detected by optical emission spectroscopy measurements, showing an increasing intensity of N( 2 P) with increasing voltage.

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A Computational Study on the Insertion of N(2D) into a C—H or C—C Bond: The Reactions of N(2D) with Benzene and Toluene and Their Implications on the Chemistry of Titan

Cited by 8 publications

References 53 publications

The N(²D) + CH₂CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan

The N(²D) + CH₂CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan

The Reaction N(²D) + CH₃CCH (Methylacetylene): A Combined Crossed Molecular Beams and Theoretical Investigation and Implications for the Atmosphere of Titan

Excited-State N Atoms Transform Aromatic Hydrocarbons into N-Heterocycles in Low-Temperature Plasmas

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A Computational Study on the Insertion of N(2D) into a C—H or C—C Bond: The Reactions of N(2D) with Benzene and Toluene and Their Implications on the Chemistry of Titan

Cited by 8 publications

References 53 publications

The N(2D) + CH2CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan

The N(2D) + CH2CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan

The Reaction N(2D) + CH3CCH (Methylacetylene): A Combined Crossed Molecular Beams and Theoretical Investigation and Implications for the Atmosphere of Titan

Excited-State N Atoms Transform Aromatic Hydrocarbons into N-Heterocycles in Low-Temperature Plasmas

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The N(²D) + CH₂CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan

The N(²D) + CH₂CHCN (Vinyl Cyanide) Reaction: A Combined Crossed Molecular Beam and Theoretical Study and Implications for the Atmosphere of Titan

The Reaction N(²D) + CH₃CCH (Methylacetylene): A Combined Crossed Molecular Beams and Theoretical Investigation and Implications for the Atmosphere of Titan