Photolysis of and reactions of hydrogen atoms with ethanethiol

Lam, W. W.; Yokota, T.; Safarik, I.; Strausz, O. P.

doi:10.1016/1010-6030(89)85005-1

Cited by 12 publications

(4 citation statements)

References 22 publications

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“…In the repulsive portion of the potential, an H (initially connected to S) atom should move away from the C–C–S skeleton of the parent molecule, even in a matrix environment (where H atoms still enjoy substantial mobility). When the H atom and C–C–S skeleton become sufficiently separated, one obtains the products C 2 H 5 S and H, which although not easily observed in our experiments, are the primary products observed upon UV photolysis of gas-phase C 2 H 5 SH . Aside from the repulsive portions of the triplet surface, there are also two clear minima: the first is close to the geometry of the H 2 CS/CH 4 complex (blue region between the 30 and 60 °C–S–H angle and ∼3 Å S–H distance), and the second is close to the geometry of the S/C 2 H 6 complex (blue region near the 30 ° C–S–H angle and ∼2 Å S–H distance).…”

Section: Resultssupporting

confidence: 47%

UV Photolysis of C₂H₅SH in Solid CO and Ar

Purzycka

Custer

Gronowski

2021

ACS Earth Space Chem.

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Ethanethiol (C2H5SH) contains the −SH group, a functional group considered to be crucial for the prebiotic polymerization of amino acids. Ethanethiol is also one of about 250 molecules detected in the interstellar medium or circumstellar shells. We irradiated C2H5SH embedded in carbon monoxide (CO) as well as argon (Ar) ices. Using spectroscopy, we detected methane (CH4), ethane (C2H6), ethylene (C2H4), acetylene (C2H2), carbon monosulfide (CS), carbonyl sulfide (OCS), dihydrogen sulfide (SH2), thioformaldehyde (H2CS), ethanethial (CH3CHS), thiirane, ethenethione (H2CCS), ethynethiol (HCCSH), thiirene, ethenedithione (SCCS), methylene radical (CH2), ethylthiyl radical (C2H5S), thioketenyl radical (HCCS), sulfanyl radical (SH), and sulfur atoms. Additionally, we observed OCS luminescence during annealing of the Ar matrix sample, which indicates the existence of a free sulfur atom. All products contain fewer atoms than the parent. CH3CHS was the main organic product in CO; OCS is the only product detected that formed due to a reaction with CO. Quantum chemical computations show that the S–H bond can easily be broken upon electronic excitation. Although more experimental and theoretical data are needed, we suggest that C2H5SH can exist only in interstellar clouds shielded from UV radiation like G+0.693-0.027 but not in Orion KL.

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Section: Resultssupporting

confidence: 47%

UV Photolysis of C₂H₅SH in Solid CO and Ar

Purzycka

Custer

Gronowski

2021

ACS Earth Space Chem.

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“…For propane, tert -butane, and neopentane, experiments were done to estimate only the total hydrogen abstraction rate coefficient. For the latter two systems, the only reliable measurement is from Baldwin and Walker at 753 K. Experiments on chloroethane and ethanol illustrate the occurrence of secondary hydrogen abstraction whereas in thioethanol the hydrogen from SH is more labile than the C−H hydrogens. With unsaturated substituents, addition across the unsaturated bond is often the preferred pathway over abstraction at low T , and it competes with abstraction at high T .…”

Section: Resultsmentioning

confidence: 99%

Reaction Rate Predictions Via Group Additivity. Part 3: Effect of Substituents with CH₂as the Mediator

2002

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has been developed on the basis of ab initio quantum chemical calculations to express the generic reaction rate in terms of the thermochemical contributions of the reactive moiety ("supergroup") in the transition structure. The supergroups are derived with the assumption that the contribution from the unreactive moiety to the thermochemistry is given by its group additivity (GA) values. This paper presents the qualitative justification for partitioning the energy of the transition structure into contributions from unreactive and reactive moieties using atoms in molecule (AIM) analysis. The couplings between these moieties, if any, are studied quantitatively using quantum chemical calculations at the CBS-Q level on reactions of the type). The present work thus focuses on the strength and limitations of the GA procedure and explores the effects of varying electronegative and bulky non-next-neighbor substituents, which are separated from the reactive center by a CH 2 group, on supergroup values. Both the C-H bond dissociation energies (BDE) and barrier heights to these reactions vary appreciably depending on the non-next-neighbor substituent, X. The preferred conformation around the XCH 2 ---CH 2 (HY) bond in transition structures is largely determined by the effective hyperconjugative interaction between the bonds of the CH 2 X group and the forming radical center. The effect of X on reaction barriers is subsequently modeled through a multilinear expression that is based on its inductive, steric, and hyperconjugative parameters, suggesting a practical way to accommodate non-next-neighbor effects on generic rate rules predicted using group additivity.

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“…CH3CH(SH)CH2CH3 -*CH3 + *CH(SH)CH2CH3 (8) CH3CH(SH)CH2CH3 -#CH2CH3 + *CH(SH)CH3 (9) For 2-butanethiol and 3-methyl-2-butanethiol, a C-C bond cleavage is indicated by an intense signal at m/z 61, which is assigned to the photoionized product *CH(SH)CH3 in reaction 9. The corresponding alkyl radicals are also observed as ions in the mass spectra (m/z 29 and 43 respectively for 2-butanethiol and 3-methyl-2-butanethiol).…”

Section: Ch3ch(sh)ch3mentioning

confidence: 99%

“…Liquid-phase and high-pressure gasphase photolysis of methanethiol, ethanethiol, and 2-methyl-2propanethiol have been reported. [5][6][7][8][9] In these experiments, bimolecular and biradical processes were dominant so the primary photodissociation reactions had to be inferred through stable * Author to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Unimolecular photochemistry of alkanethiols studied by photodissociation-photoionization mass spectrometry

Ross¹,

Johnston²

1993

J. Phys. Chem.

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Unimolecular photodissociation of isomeric alkanethiols in the C3 to c 8 size range was studied by using photodissociation-photoionization mass spectrometry. Photodissociation was performed with 193-and 248-nm radiation. The primary products were photoionized with coherent vacuum ultraviolet radiation and detected in a time-of-flight mass spectrometer. Three basic reaction channels were observed: C S , C-C, and S-H bond dissociation. The branching ratios for fragmentation through thesechannels were found to be strongly dependent upon molecular structure and photodissociation wavelength. All compounds gave intense products of C S bond dissociation. Photoionization and secondary fragmentation characteristics of the primary products suggested that complete statistical partitioning of the excess internal energy did not occur. Small molecules gave C-C bond dissociation at the a position, while larger molecules showed increasing probability for cleavage at the p and y positions. Cleavage of the a C-C bond was strongly suppressed relative to other reaction channels when the expected product was a methyl radical. Complex rearrangements were observed for molecules exhibiting suppression of C-C bond dissociation. Cleavage of the S-H bond was unambiguously observed only for small molecules ( I C s ) . The branching ratio for cleavage of the S-H bond was greater at 248 nm than 193 nm. This behavior is consistent with the excited-state electronic configurations, which show a greater contribution from U*SH at 248 nm than at 193 nm. Both the S-H and C S bond dissociation characteristics suggest that the excited electronic state plays an important role in the photodissociation process.

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Photolysis of and reactions of hydrogen atoms with ethanethiol

Cited by 12 publications

References 22 publications

UV Photolysis of C₂H₅SH in Solid CO and Ar

UV Photolysis of C₂H₅SH in Solid CO and Ar

Reaction Rate Predictions Via Group Additivity. Part 3: Effect of Substituents with CH₂as the Mediator

Unimolecular photochemistry of alkanethiols studied by photodissociation-photoionization mass spectrometry

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Photolysis of and reactions of hydrogen atoms with ethanethiol

Cited by 12 publications

References 22 publications

UV Photolysis of C2H5SH in Solid CO and Ar

UV Photolysis of C2H5SH in Solid CO and Ar

Reaction Rate Predictions Via Group Additivity. Part 3: Effect of Substituents with CH2as the Mediator

Unimolecular photochemistry of alkanethiols studied by photodissociation-photoionization mass spectrometry

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Product

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UV Photolysis of C₂H₅SH in Solid CO and Ar

UV Photolysis of C₂H₅SH in Solid CO and Ar

Reaction Rate Predictions Via Group Additivity. Part 3: Effect of Substituents with CH₂as the Mediator