Semiempirical Potential in Kinetics Calculations on the HC3N + CN Reaction

Aragão, Emília Valença Ferreira de; Mancini, Luca; Faginas-Lago, Noelia; Rosi, Marzio; Skouteris, Dimitrios; Pirani, Fernando

doi:10.3390/molecules27072297

Cited by 3 publications

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References 63 publications

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“…HC 3 N is a molecule with a recognized prebiotic potential (as many unsaturated nitriles), and therefore, within the framework of the Italian National Project of Astrobiology, we have recently investigated its reactions with other reactive radicals that are abundant in extraterrestrial environments where HC 3 N has been identified, such as N( 2 D) (Titan and comets) and CN − (also unpublished results) (Titan, interstellar clouds, and comets). This work is providing another piece in the puzzle of cyanoacetylene chemistry in space.…”

Section: Introductionmentioning

confidence: 99%

Reactions O(³P, ¹D) + HCCCN(X¹Σ⁺) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments

et al. 2023

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Cyanoacetylene (HCCCN), the first member of the cyanopolyyne family (HC n N, 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, E c, 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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Section: Introductionmentioning

confidence: 99%

Reactions O(³P, ¹D) + HCCCN(X¹Σ⁺) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments

et al. 2023

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A Computational Study of the Reaction Between N(2D) and Simple Aromatic Hydrocarbons

Rosi

Balucani

Casavecchia

et al. 2023

Lecture Notes in Computer Science

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Crossed molecular beam studies of bimolecular reactions of atomic oxygen with nitrogen-bearing organic molecules (nitriles and N-heterocyclic)

Pannacci,

Vanuzzo,

Balucani

et al. 2024

Rend. Fis. Acc. Lincei

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In this contribution, dedicated to the memory of Prof. Gian Gualberto Volpi, we provide a short review of recent work carried out in our laboratory on reactive scattering studies of the reaction dynamics of atomic oxygen with nitrogen-bearing organic molecules. Specifically, we focus on the polyatomic bimolecular reactions of atomic oxygen, both in the ground and first excited state, O(3P) and O(1D), with the simplest unsaturated nitriles, namely HCCCN (cyanoacetylene) and CH2CHCN (cyanoethylene, or acrylonitrile), and with the simplest six-member ring N-heterocyclic compound, pyridine (C5H5N). Using the crossed molecular beam (CMB) scattering technique with universal electron-impact ionization mass-spectrometric detection and time-of-flight analysis to measure product angular and velocity distributions, the primary product channels and their branching fractions were determined, thus assessing the central role played by intersystem-crossing (ISC) in this class of reactions. The experimental work was synergistically accompanied by theoretical calculations of the relevant triplet and singlet potential energy surfaces (PESs) to assist the interpretation of experimental results and elucidate the reaction mechanism, including extent of ISC. Cyanoacetylene and cyanoethylene are of considerable interest in astrochemistry being ubiquitous (and relatively abundant) in space including comets and the upper atmosphere of Titan. Being oxygen the third most abundant element in space, the title reactions are of considerable relevance in the chemistry of extraterrestrial environments. In addition, they are also important in combustion chemistry, because thermal decomposition of pyrrolic and pyridinic structures present in bound N-containing fuels generates N-bearing compounds including, in particular, the above two nitriles.

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Semiempirical Potential in Kinetics Calculations on the HC3N + CN Reaction

Cited by 3 publications

References 63 publications

Reactions O(³P, ¹D) + HCCCN(X¹Σ⁺) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments

Reactions O(³P, ¹D) + HCCCN(X¹Σ⁺) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments

A Computational Study of the Reaction Between N(2D) and Simple Aromatic Hydrocarbons

Crossed molecular beam studies of bimolecular reactions of atomic oxygen with nitrogen-bearing organic molecules (nitriles and N-heterocyclic)

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Semiempirical Potential in Kinetics Calculations on the HC3N + CN Reaction

Cited by 3 publications

References 63 publications

Reactions O(3P, 1D) + HCCCN(X1Σ+) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments

Reactions O(3P, 1D) + HCCCN(X1Σ+) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments

A Computational Study of the Reaction Between N(2D) and Simple Aromatic Hydrocarbons

Crossed molecular beam studies of bimolecular reactions of atomic oxygen with nitrogen-bearing organic molecules (nitriles and N-heterocyclic)

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Reactions O(³P, ¹D) + HCCCN(X¹Σ⁺) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments

Reactions O(³P, ¹D) + HCCCN(X¹Σ⁺) (Cyanoacetylene): Crossed-Beam and Theoretical Studies and Implications for the Chemistry of Extraterrestrial Environments