Chemical Behavior of Polycyanoacetylene Radicals on Gaseous and Ice Water: A Computational Perspective

Xie, Hongbin; Shi, Guosheng; Ye, Ding

doi:10.1086/511172

Cited by 4 publications

(2 citation statements)

References 49 publications

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“…Because reaction ii is a radiative association process, the final product is expected to be stabilized by photon emission; otherwise, the excess energy would lead to back dissociation to the initial reactants, as already proposed in the case of the formation cyanoacetaldehyde. 17 computational investigation of reaction iii by Xie et al 18 showed that it cannot occur at very low temperatures because of a non-negligible energy barrier for the hydrogen abstraction.…”

Section: Introductionmentioning

confidence: 99%

“…For this reason, Margulés et al considered this reaction unlikely in the ISM but possible on grain surfaces. Finally, a computational investigation of reaction iii by Xie et al showed that it cannot occur at very low temperatures because of a non-negligible energy barrier for the hydrogen abstraction. The same authors also studied the catalytic effect of water on the reaction and found that, with the increase of the number of catalyzing water molecules, the reaction becomes barrierless.…”

Section: Introductionmentioning

confidence: 99%

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Toward the Detection of Cyanoketene in the Interstellar Medium: New Hints from Quantum Chemistry and Rotational Spectroscopy

Ballotta

Marforio

Rampino

et al. 2023

ACS Earth Space Chem.

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A detailed quantum chemical investigation of a new reaction mechanism possibly leading to the formation of cyanoketene (NC–CHCO) in the interstellar medium (ISM) was carried out. Different reaction channels have been found by the AutoMeKin program, and the structures and harmonic force fields of the key stationary points have been characterized at the density functional theory level employing last-generation double-hybrid functionals. Finally, single-point computations at those geometries by state-of-the-art composite wave function methods provided accurate energies for the evaluation of thermochemical and kinetic parameters in the framework of an Ab Initio Transition State Theory based Master Equation (AITSTME) strategy. Our results indicate that the barrier-less association reaction of the formyl radical (HCO•) to the cyanocarbene radical (HCCN) can lead to the formation of cyanoketene under the harsh conditions of the ISM. Canonical rate constants computed for temperatures up to 600 K show that the most abundant product is indeed cyanoketene. The formation of other, even more stable, species involves higher activation energies and/or less favorable multi-step processes. Furthermore, to aid the search of cyanoketene, still undetected in the ISM, its rotational spectrum was recorded up to 530 GHz. The refined set of spectroscopic constants obtained in this way allows for spectral predictions from the microwave to the terahertz region, particularly for the bright b-type transitions, which can be targeted for the identification of cyanoketene in spectral line surveys. Despite cyanoketene was already sought without success in a variety of astronomical sources, we suggest to look for it in those sources where HCO or HCCN have already been detected, namely, W3, NGC2024, W51, K3-50, IRC + 2016, and TMC-1.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Toward the Detection of Cyanoketene in the Interstellar Medium: New Hints from Quantum Chemistry and Rotational Spectroscopy

Ballotta

Marforio

Rampino

et al. 2023

ACS Earth Space Chem.

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Understanding the oxidation of the tricarbon radical C₃ H: A reaction pathway survey

Zhu

Jin

Cui

et al. 2013

Int. J. Quantum Chem.

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The very recent observation of molecular oxygen in interstellar space appeals for the great need of mechanistic understanding of the oxidation processes of various interstellar species. In this article, we report for the first time, the oxidation mechanism of the chainlike l-C 3 H by molecular oxygen, which is known as one of the interesting carbon-chain hydrocarbon series C n H detected in space. This reaction is also relevant to the combustion processes where various carbon hydrides are involved. The detailed reaction pathways were identified at the CCSD(T)=aug-cc-pVTZ==B3LYP=6-31111G(d,p)1ZPVE level including various fragmentation channels. Three types of fragmentation channels are identified as the C-transfer product P 2 (CO 2 1C 2 H) (2129.2kcal=mol), the C,O-exchange product P 1 (CO1HC 2 O) (2154.7kcal=mol), and the O-transfer product P 6 ( 3 O1HC 3 O) (244.8kcal=mol). The initially entered unstable dioxygen isomer 1a HCCCOO (226.6 kcal/mol) would either undergo the direct O-extrusion to give P 6 (the intrinsic barrier 7.5 kcal=mol) or take a 1,2-O-shift (0.8 kcal=mol barrier) to give a stable isomer 5 HCCC(O)O (2139.2kcal=mol) that can either dissociate to P 1 or to P 2 . The intrinsic barrier from 5 to P 1 and P 2 is 29.1 and 23.6 kcal=mol, respectively. Clearly, the entrance thermicity 26.6 kcal=mol of 1a can sufficiently initiate the subsequent formation of all the three products. To quantitatively evaluate the kinetic competition of the three products, we performed the master equation rate constant calculations. It was shown that at 298 K, the most favorable product is P 2 (64.8%) followed by P 6 (23.6%), and P 1 (11.6%). Interestingly, at elevated temperatures, the ratio of P 6 increases with the decrease of P 2 , whereas that of P 1 is little changed. Notably, the thermodynamically most stable product P 1 is kinetically the least favorable, indicative of the importance of considering the kinetics. The dominant formation of P 2 (CO 2 1C 2 H) shows that the important carbyne radical l-C 3 H can be effectively degraded by O 2 via the chain-shortening step. The reactivity of the cyclic c-C 3 H radical toward O 2 is also discussed. The results are expected to enrich our understanding of the chemistry of the simplest C 3 -radical in both combustion and interstellar processes.

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Synergistic effects between hydroxyl radicals and hydrated electrons on strengthening decomposition of an s-triazine compound: A combined experimental and theoretical study

et al. 2018

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Chemical Behavior of Polycyanoacetylene Radicals on Gaseous and Ice Water: A Computational Perspective

Cited by 4 publications

References 49 publications

Toward the Detection of Cyanoketene in the Interstellar Medium: New Hints from Quantum Chemistry and Rotational Spectroscopy

Toward the Detection of Cyanoketene in the Interstellar Medium: New Hints from Quantum Chemistry and Rotational Spectroscopy

Understanding the oxidation of the tricarbon radical C₃ H: A reaction pathway survey

Synergistic effects between hydroxyl radicals and hydrated electrons on strengthening decomposition of an s-triazine compound: A combined experimental and theoretical study

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Chemical Behavior of Polycyanoacetylene Radicals on Gaseous and Ice Water: A Computational Perspective

Cited by 4 publications

References 49 publications

Toward the Detection of Cyanoketene in the Interstellar Medium: New Hints from Quantum Chemistry and Rotational Spectroscopy

Toward the Detection of Cyanoketene in the Interstellar Medium: New Hints from Quantum Chemistry and Rotational Spectroscopy

Understanding the oxidation of the tricarbon radical C3 H: A reaction pathway survey

Synergistic effects between hydroxyl radicals and hydrated electrons on strengthening decomposition of an s-triazine compound: A combined experimental and theoretical study

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Understanding the oxidation of the tricarbon radical C₃ H: A reaction pathway survey