Reactions of thiyl radicals. VI. Photolysis of ethanethiol

1969 ◽  
Vol 47 (8) ◽  
pp. 1335-1345 ◽  
Author(s):  
R. P. Steer ◽  
A. R. Knight
Keyword(s):  
Bond Cleavage ◽  
Addition Product ◽  
Inert Gas ◽  
Effect Of Temperature ◽  
Primary Process ◽  
Hydrogen Atoms ◽  
Diethyl Sulfide ◽  
Rate Constant Ratio ◽  
Olefinic Double Bond ◽  
A Chain

The photolysis of ethanethiol vapor in the pressure range 10 to 350 Torr and the effect of % decomposition, wavelength, and of added inert gas and ethylene on the rate of formation of the products has been determined. In addition, the effect of temperature on the photolysis of methanethiol–ethylene–inert gas and ethanethiol–ethylene–inert gas systems has been studied.For the pure substrate, the primary process is S—H bond cleavage and the hydrogen atom produced abstracts the sulfyhydryl hydrogen of the substrate. The quantum yield of molecular hydrogen formation is unity, independent of pressure. C2H5S radicals, formed either in the primary process or as a result of abstractive attack by H atoms or radicals on the substrate, combine to form an excited disulfide molecule. The major condensable product, C2H5SSC2H5, arises via collisional deactivation of this excited species which can also sensitize the decomposition of the substrate to give C2H4, C2H6, and H2S, the other products observed. With added inert gas the rates of formation of the minor products decrease whereas hydrogen and disulfide remain unchanged.With added ethylene, the major products are H2, C2H5SSC2H5, and C2H5SC2H5, the addition product. Diethyl sulfide is formed in a chain reaction by the attack of C2H5S on the olefinic double bond to form the composite radical, followed by H abstraction from the substrate. The hydrogen rate decreases due to the addition of H atoms to ethylene. The rate constant ratio, k22/k4, for the reactions [22] and [4], respectively,[Formula: see text]is pressure dependent, indicative of the formation of hot hydrogen atoms in the primary process of the photolysis of methanethiol and ethanethiol. The Arrhenius parameters A22/A4 and E22−E4 for the methanethiol–ethylene and ethanethiol–ethylene systems have been determined. Kinetic treatments of the proposed mechanisms have been undertaken.

Reactions of hot hydrogen atoms in mercaptan–ethylene systems

1968 ◽  
Vol 46 (17) ◽  
pp. 2878-2880 ◽  
Author(s):  
R. P. Steer ◽  
A. R. Knight
Keyword(s):  
Rate Constant ◽  
Inert Gas ◽  
Primary Process ◽  
Process Rate ◽  
Hydrogen Atoms ◽  
Process Rate Constant

Investigation of the photolysis of methanethiol and ethanethiol vapor in the presence of ethylene and inert gas has indicated the formation of energetic hydrogen atoms in the primary process. Rate constant ratios for the reactions of these species have been found to be pressure dependent.

Hg(63P1)-sensitized decomposition of HNCO vapor and HNCO–H2 mixtures; the reaction of hydrogen atoms with HNCO

1968 ◽  
Vol 46 (4) ◽  
pp. 527-530 ◽  
Author(s):  
N. J. Friswell ◽  
R. A. Back
Keyword(s):  
Quantum Yield ◽  
Cross Section ◽  
Initial Step ◽  
Primary Process ◽  
Hydrogen Atoms ◽  
Direct Photolysis ◽  
A Value ◽  
The Cross

The Hg(63P1)-sensitized decomposition of HNCO vapor has been briefly studied at 26 °C with HNCO pressures from about 3 to 30 Torr. The products detected were the same as in the direct photolysis, CO, N2, and H2. The quantum yield of CO was appreciably less than unity, compared with a value of 1.5 in the direct photolysis under similar conditions. From this and other observations it is tentatively concluded that a single primary process occurs:[Formula: see text]From a study of the mercury-photosensitized reactions in mixtures of HNCO with H2, it was concluded that hydrogen atoms react with HNCO to form CO but not N2. The initial step is probably addition to form NH2CO. From the competition between reaction [1] and the corresponding quenching by H2, the cross section for reaction [1] was estimated to be 2.3 times that of hydrogen.

Effect of Hydrogenation Temperature on Distribution of Hydrogen Atoms in c-Si and a-Si: Molecular Dynamic Simulations

2016 ◽  
Vol 706 ◽  
pp. 55-59 ◽  
Author(s):  
Mauludi Ariesto Pamungkas ◽  
Rendra Widiyatmoko
Keyword(s):  
Amorphous Silicon ◽  
Silicon Surface ◽  
Prolonged Exposure ◽  
Crystalline Silicon ◽  
Transfer Hydrogenation ◽  
Effect Of Temperature ◽  
Hydrogen Atoms ◽  
Dynamic Simulations ◽  
Hydrogenation Temperature ◽  
Dynamics Simulations

Crystalline silicon and amorphous silicon are main materials of solar cell. Under prolonged exposure to light, silicon will degrade in quality. Hydrogenation is believed can minimize this degradation by reduce the number of dangling bond. These Molecular dynamics simulations are aimed to elaborate the hydrogenation process of crystalline silicon and amorphous silicon and to elucidate effect of temperature on distribution of hydrogen atoms. Reactive Force Field is selected owing to its capability to describe forming and breaking of atomic bonds as well as charge transfer. Hydrogenation is performed at 300 K, 600 K, 900 K, and 1200 K. Hydrogenated silicon surface hinders further hydrogen atoms to be absorbed such that not all deposited Hydrogen atoms are absorbed by silicon surface. Generally, the higher hydrogenation temperature the more hydrogen atoms are absorbed. Increment of temperature from 900 K to 1200 K only enhances a few numbers of absorbed hydrogen atoms. However, it can enable hydrogen atoms to penetrate into deeper silicon substrate. It is also observed that hydrogen atoms can penetrate into amorphous silicon deeper than into crystalline silicon.

The effect of meta- and para-methoxy substitution on the reactivity of the radical cations of arylalkenes and alkanes. Radical ions in photochemistry. Part 26

1991 ◽  
Vol 69 (5) ◽  
pp. 839-852 ◽  
Author(s):  
Donald R. Arnold ◽  
Xinyao Du ◽  
Kerstin M. Henseleit
Keyword(s):  
Electron Transfer ◽  
Radical Cation ◽  
Bond Cleavage ◽  
Cation Radical ◽  
Radical Cations ◽  
Addition Product ◽  
Molecular Orbital Calculations ◽  
Carbon Carbon Bond ◽  
Markovnikov Addition ◽  
Cis And Trans

The effect of meta- and para-methoxy substitution on the reactivity of some radical cations has been determined. The compounds chosen for study were 1-(3-methoxyphenyl)-1-phenylethylene (7), 1-(4-methoxyphenyl)-1-phenylethylene (8), 3-(3-methoxyphenyl)indene (9), 3-(4-methoxyphenyl)indene (10), methyl 2-(3-methoxyphenyl)-2-phenylethyl ether (11), methyl 2-(4-methoxyphenyl)-2-phenylethyl ether (12), cis- and trans-2-methoxy-1-(3-methoxyphenyl)indane (13), and cis- and trans-2-methoxy-1-(4-methoxyphenyl)indane (14). The radical cations of these compounds were generated by photosensitization (electron transfer) using 1,4-dicyanobenzene (3) as the electron acceptor. The three reactions studied were: (1) The addition of nucleophiles (methanol) to the radical cation of the arylalkenes, a reaction that yields the anti-Markovnikov addition product. (2) The carbon–carbon bond cleavage of radical cations, which yields products derived from the radical and carbocation fragments. (3) The deprotonation of the radical cation, a reaction that can be used to invert the configuration at a saturated carbon centre. The mechanisms of these reactions are discussed and the factors that need to be considered in order to predict reactivity are defined. Molecular orbital calculations (UHF/STO-3G) were carried out on the radical cations of the model compounds 3- and 4-vinylanisole and 3- and 4-methylanisole. Key words: photochemistry, photosensitize (electron transfer), radical cation, radical.

Oxidation ot sultur compounds. I. The photolysis of CH3SH and (CH3S)2 in the presence of NO

1984 ◽  
Vol 62 (1) ◽  
pp. 162-170 ◽  
Author(s):  
R. Jeffrey Balla ◽  
Julian Heicklen
Keyword(s):  
Mass Spectrometer ◽  
Quadrupole Mass Spectrometer ◽  
Chain Process ◽  
Quadrupole Mass ◽  
Product Analysis ◽  
Hydrogen Atoms ◽  
A Chain

Both CH3SH and (CH3S)2, as well as their mixtures, were photolyzed in the presence of NO at 23 ± 1 °C. The photolyses were carried out in a 631 mL quartz vessel with a pinhole bleed to a quadrupole mass spectrometer for continual analysis of products. After the termination of exposure, further product analysis was made by gas chromatography.The identified products of the reaction were CH3SNO, (CH3S)2, H2, and N2. Hydrogen atoms, formed from the photolysis of CH3SH, reacted with both NO and CH3SH:[Formula: see text]with k5/k4 = 626 ± 42 Torr for NO as a chaperone. The CH3S radical adds to NO[Formula: see text]with k−2a/k2b = 83 ± 52 Torr. As the CH3SNO accumulates, CH3S also reacts with CH3SNO[Formula: see text]with [Formula: see text]. At high NO pressures a chain process occurs which is attributed to:[Formula: see text]where ξ is probably 4.0. Termination is most easily represented by[Formula: see text]with k8/k7 = 85.0 ± 7.8 Torr

scholarly journals Insights into the Active Sites and Kinetics of Double-site Catalysts for Semi-hydrogenation under Hydrogen Spillover

2021 ◽  
Author(s):  
Shuai Wang ◽  
Yipin Lv ◽  
Xilong Wang ◽  
Daowei Gao ◽  
Aijun Duan ◽  
...  
Keyword(s):  
Active Sites ◽  
Au Nanoparticles ◽  
Hydrogen Spillover ◽  
Mesoporous Zeolite ◽  
Hydrogen Atoms ◽  
Au Nps ◽  
Pt Nanoclusters ◽  
Hydrogen Molecules ◽  
Rate Constant Ratio ◽  
Kinetics Of

A well-defined catalyst with platinum (Pt) and gold (Au) encapsulated in micropore and mesopore of micro-mesoporous zeolite (TMSN), respectively, was designed to investigate the original active sites and kinetics of semi-hydrogenation. Specifically, hydrogen molecules are dissociated on Pt nanoclusters (NCs) to form hydrogen atoms that migrate to the surfaces of TMSN zeolite and Au nanoparticles (NPs). Meanwhile, the Au NPs with inferior H dissociation capability in the mesopore can be served as the detector and controller of hydrogen spillover. The Pt NCs in micropore act as H dissociation sites while both the Au NPs and zeolite surface are identified as the semi-hydrogenation sites. Noteworthy, the Pt-Au/TMSN catalyst with double active sites exhibits higher selectivity and rate constant ratio for semi-hydrogenation than Pt/TMSN, as well as higher turnover frequency (TOF) than Au/MSN. This work creates an effective regulation strategy of hydrogen spillover for improving active sites and kinetics of semi-hydrogenation.

Photolysis of, and the reactions of H-atoms with, isopropanethiol

1988 ◽  
Vol 66 (8) ◽  
pp. 2025-2033 ◽  
Author(s):  
W. W. Lam ◽  
T. Yokota ◽  
I. Safarik ◽  
O. P. Strausz
Keyword(s):  
Rate Constant ◽  
Thermal Reaction ◽  
Inert Gas ◽  
Constant Ratio ◽  
Temperature Range ◽  
Rate Constant Ratio ◽  
Photolytic Decomposition

Detailed investigation of the photolysis of i-C3H7SH has been carried out in the absence and presence of the inert gas, n-C4H10. A mechanism consisting of three primary photochemical steps: [Formula: see text], [Formula: see text]; [Formula: see text], [Formula: see text]; [Formula: see text],[Formula: see text]; six hot reaction steps and seven thermal reaction steps adequately explains all the experimental observations. As in the case of hot H* atoms both the H-atom abstraction, [Formula: see text], and the SH-displacement, [Formula: see text], reactions occur with thermalized H-atoms, with the rate constant ratio k7/k8 = 19.2 ± 4.3 at 25 °C. The Arrhenius expressions have been determined over the temperature range 25–145 °C, to be: k7 = (4.0 ± 0.7) × 1012 exp [(−1066 ± 43)/RT] and k8 = (2.8 ± 0.6) × 1012 exp[(−2597 ± 114)/RT] cm3 mol−1 s−1. It was found that the overall mechanism for the photolytic decomposition of i-C3H7SH is analogous to that established for C2H5SH in previous investigations.

La décomposition du tétraméthylgermane par les atomes Hg 6(3P1)

1973 ◽  
Vol 51 (18) ◽  
pp. 3062-3064 ◽  
Author(s):  
Jocelyn Duval ◽  
Yves Rousseau
Keyword(s):  
Quantum Yield ◽  
Bond Cleavage ◽  
Primary Process ◽  
Methyl Radicals ◽  
Mild Conditions

The primary process in the mercury photosensitized decomposition of tetramethylgermane is a C—H bond cleavage. The hydrogen quantum yield, extrapolated at infinite pressure, is close to unity. Under mild conditions, hydrogen and 1,2-di(trimethylgermyl) ethane are the only products observed. At high intensities and low substrate pressures, atomic cracking occurs yielding methyl radicals which lead to the formation of methane.

Effect of temperature on the growth of inert gas bubbles in metals

1990 ◽  
Vol 172 (1) ◽  
pp. 114-122 ◽  
Author(s):  
G.P. Tiwari ◽  
J. Singh
Keyword(s):  
Gas Bubbles ◽  
Inert Gas ◽  
Effect Of Temperature

THE MECHANISM OF POLYMERIZATION REACTIONS

1932 ◽  
Vol 7 (1) ◽  
pp. 113-114 ◽  
Author(s):  
William Chalmers
Keyword(s):  
Reaction Mechanism ◽  
Double Bond ◽  
Hydrogen Atoms ◽  
Chain Reaction ◽  
A Chain

Attention is called to an earlier, unpublished writing by the author wherein a chain-reaction mechanism was suggested for all polymerizations leading to macro-molecular products. It is further pointed out that the only scheme of reaction which is compatible with this mechanism is that which involves only the double bond, i.e., the possibility of the changes taking place by the transference of hydrogen atoms is practically excluded.

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