Reactions of thioyl radicals. IV. Photolysis of methanethiol

Professor Harry E. Gunning on the occasion of his 65th birthday R. JEFFREY BALLA and JULIAN HEICKLEN. Can. J. Chem. 62, 162 (1984).Both CH,SH and (CH,S),, as well as their mixtures, were photolyzed in the presence of NO at 23 * 1°C. The photolyses were carried out in a 63 1 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 CHSNO, (CH3S)?, HZ, and N,. Hydrogen atoms, formed from the photolysis of CH3SH, reacted with both NO and CH3SH:[4]with ks/k, = 626 '-42 Ton for NO as a chaperone. The CH,S radical adds to NO

Section: Resultssupporting

confidence: 88%

“…The photolysis of CH,SH in the presence of NO has been studied by Steer and Knight (1). ' They studied the reaction in steady-state photolysis and analyzed the products after termination of irradiation.…”

Section: Introductionmentioning

confidence: 99%

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

Balla¹,

Heicklen²

1984

“…as a majority product in spite of the fact that the C-S and not the S-N bond is the weakest in the molecule (11,29). This finding is in agreement with sulfhydryl photolysis experiments carried out in the vapor phase (11).…”

Section: A Photolysissupporting

confidence: 88%

“…The effect of radiation or of photolytic absorption on the pure mercaptans has been extensively studied in the gaseous state (11,12), in the solid polycrystalline state (13,14), and in single crystals such as cysteine (15,16). The metastable intermediates of chemical oxidation in dilute aqueous solutions have also been studied using fast flow techniques (17,18), flash photolysis (19), or pulse radiolysis methods (20), but until recently not much work had been done on the radiolysis and photolysis of thlols in dilute rigid solutions using inert or chemically indifferent organic matrices.…”

Section: Introductionmentioning

confidence: 99%

The Photolysis and Radiolysis of Simple Mercaptans in Dilute Glassy Matrices

Skelton¹,

Adam²

1971

The e.p.r. spectrum of thiyl radicals is obtained when dilute solutions of aliphatic mercaptans are photolyzed in a xenon matrix at 77 OK. No proton hyperfine structure is observed at low concentrations of thiol but it appears at higher concentrations due to the reaction of hot hydrogen atoms with solute mercaptan molecules. When small amounts of the thiols are dissolved in glassy hydrocarbon matrices such as 3-methylpentane, there is produced after photolysis hyperfine structure characteristic of the solvent as well as the thiyl resonance. The e.s.r. absorption due to the solvent species disappears when the matrix is warmed a few degrees above 77 "K but thiyl radicals are stable up to the melting point of the glass. The corresponding y-irradiated glasses do not give thiyl absorption, but two other species are produced along with solvent radicals. No thiyl radicals are observed following radiolysis, or upon photobleaching the new species. The spatial distribution of the neutral radicals in the glasses is discussed in view of these results.Le spectre de r.p.e. de radicaux thiyl est obtenu lors de la photolyse de solutions dilukes de mercaptans aliphatiques dans une matrice de xenon a 77 OK. On n'observe pas la structure hyperfine du proton en utilisant de faibles concentrations de thiol, mais elle apparait lorsqu'on utilise des concentrations plus ClevCes a cause de la reaction des atomes d'hydrogkne chauds avec les molCcules de mercaptan en solution. Si on dissout de petites quantites de thiol dans des matrices d'hydrocarbure vitreuses, tel le methylpentane-3, il se produit apres photolyse, une structure hyperfine qui est caracteristique du solvant aussi bien que de la resonance du thiyl. L'absorption r.p.e. due a l'espece solvant disparait quand la matrice est chauffee a quelques degris au-dessus de 77 OK, mais les radicaux thiyl demeurent stables jusqu'au point de fusion du verre. Les verres irradits aux rayons-y ne donnent pas d'absorption thiyl, mais deux autres especes sont produites en meme temps que les radicaux de solvant. On n'observe pas de radicaux thiyl apres radiolyse, ou pendant la photodCcoloration des nouvelles espkces. On discute de la distribution spatiale des radicaux neutres dans les verres pour arriver aces rksultats.

“…Results obtained in this laboratory have indicated a maximum value of ca. 0.05 for the disproportionation/recombination ratio for thiyl radicals formed in the direct photolysis of thiols (7,8) and disulfides (9,10) in the vapor phase. In the liquid phase, disproportionation is virtually negligible (1 I).…”

Section: Introductionmentioning

confidence: 99%

Reactions of Thiyl Radicals. VII. Photolysis of Methyl Sulfide Vapor

Rao¹,

Knight²

1972

Self Cite

The photolysis of methyl sulfide vapor has been investigated as a function of substrate pressure, exposure time, and temperature in the wavelength range 2000 to 2300 Å. The effects of added propane, sulfur hexafluoride, and 2-methylpentane have been studied. The principal products of the decomposition are CH4, C2H6, CH3SSCH3, and CH3SH. The data indicate direct C—S bond scission in the primary process giving rise to "hot" CH3 and CH3S radicals. A mechanism in which disproportionation of methylthiyl radicals is a very minor process is proposed.The reactions of CH3 and CH3S radicals with methyl sulfide have been examined also by photolyzing CH3SSCH3 and CH3COCH3 in the presence of CH3SCH3. Quantum yields at 2288 Å have been determined as a function of several variables. A number of rate parameters for the reactions of methyl radicals and methylthiyl radicals have been calculated.