Identification of Intermediates in the Photolysis of Mercaptans in Dilute Glass Matrices. II

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Simple alkyl sulfides and disulfides have been photolysed at 253.7 nm in dilute rigid glasses of 3-methylpentane, and the reactions which occur both at 77 K and in the glass at higher temperatures have been studied using epr and optical spectroscopy. The end products of photolysis have been determined using glc at room temperature. In sulfides, C—S bond cleavage leads to 'hot' radical pairs that react with each other giving rise to the main diamagnetic products observed, or react with nearby solvent molecules in the matrix by hydrogen abstraction yielding RSH and the solvent derived radicals (M•) which dominate the initial epr spectrum at 77 K. Thiyl radicals (RS•) are produced in significant amounts only after the sulfide glasses have been warmed slightly to allow the cage reaction,[Formula: see text]to occur. Pethiyl radicals (RS2•) are not ordinarily observed in sulfide photolyses. Photolysis of disulfide-containing glasses gives rise to S—S bond rupture and mainly diamagnetic products, or to C—S bond cleavage resulting in the formation of solvent radicals and RS2. Very little RS• is generated on warming the matrices. As with ethyl mercaptan photolysis, radicals corresponding to α-hydrogen abstraction of the substrate are obtained for both ethyl sulfide and disulfide. The spectral characteristics and photolytic behaviour of the sulfur containing radical species have been investigated where possible.

Section: S L /~J~c /~Smentioning

confidence: 49%

Intermediates in the photolysis of alkyl sulfides and disulfides in dilute glass matrices

Adam¹,

Elliot²

1977

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“…The general procedures have been described earlier (6,7) and are analogous to those used in photolysis experiments. The solvents were purified by passage through activated silica gel columns and freshly distilled before use.…”

Section: Methodsmentioning

confidence: 99%

“…An identical absorption is 720-880 nm region are lost. The species produced obtained by 253.7 photolysis of the EtSH/BuCl glass (nay be the t h i~l radical EtS' which is known to (following slight warming) and can be attributed to absorb at 405 nnl in this particular matrix (6,7). It is the thiyl radical.…”

Section: B Alkyl Disirljiclfs (I) 2 M T H F Glassesmentioning

confidence: 99%

“…This has resulted in much more detailed investigation of the uv photolysis of simple aliphatic mercaptans (6), sulfides, and disulfides (7), dissolved at low concentration in rigid organic glasses maintained at low temperatures. In such rigid media, diffusion controlled processes (such as thiyl recombination) can be retarded so that the inetastable intermediates can be studied by conventional optical and epr techniques.…”

Section: Introductionmentioning

confidence: 99%

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Intermediates in the γ-radiolysis of diraient sulfur compounds in dilute glass matrices

Adam¹,

Smith²,

Elliot³

1978

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Can. J. Chem. 56, 1856(1978).The optical spectra of the charged ions obtained from y-irradiation of dilute alkyl niercaptans, sulfides, and disulfides in a variety of dilute rigid glasses are measured at 77 K. The photochemical stability of these ions is determined. A new photochromic species has been found. It is derived from a niercaptan dimer cation and is analogous to the photochromic anion produced from alkyl disulfides. The results of y-radiation are compared to the uv photolysis of similar matrices, and it is found that the thiyl (RS.) and perthiyl radicals (RS,.) are not generally in evidence in y-irradiated matrices although they may be obtained by appropriate annealing or photobleaching of the irradiated matrix. The ions which have been characterized optically are RSH+, RSH-, RSSR+ or their dimers, and RSS(H)R. The relative stabilities of these species in the low temperature glasses are determined.FRANK CUTHBERT ADAM, GLENN EDWARD SMITH et ALLEN JOHN ELLIOTT. Can. J. Chem. 56, 1856(1978).On a obtenu les spectres optiques d'ions portant des charges; ceux-ci ont ete prepares par irradiation y d'alkyl-niercaptans, de sulfures d'alkyle, de disulfures d'alkyle diluts dans un certain nombre de verres rigides a 77 K . On a determint la stabilite photochimique de ces ions. On a trouve une nouvelle espece photochromique. Elle derive d'un cation dimere du mercaptan et elle est analogue a I'anion photochromique obtenu a partir des disulfures d'alkyle. On a compare les rtsultats obtenus par irradiation y a ceux obtenus par photolyse uv de matrices semblables et on a trouve que les radicaux thiyl (RS.) et perthiyl (RS,.) lie se retrouvent geniralement pas dans les matrices ayant subit une irradiation y quoiqu'elles peuvent &tre obtenues si I'on recuit ou si I'on fait subir une photodecoloration appropriee a la matrice irradite. Les ions que I'on a caracterises d'une f a~o n optique sont RSH+, RSH-, RSSR+ ou leurs dimeres ainsi que RSS(H)R. On a determine les stabilites relatives d e ces especes dans des verres a basse temperature.[Traduit par le journal]

“…9 assuming the room temperature distribution is "rozen in' at 77 K. Radiolysis was carried .out using aoCo ?-rays in a Gammacell 220 from Atomic Energy of Canada Ltd. at a dose rate of 3.8 X 1016eV g-1 min-1. The photolytic procedures have been described elsewhere (10) as has the epr spectrometer used ( I I).…”

Section: Experimeratai Proceduresmentioning

confidence: 99%

Formation and photolysis of alkyl and peroxy radicals in dilute glass matrices

Adam¹,

Marshall²

1976

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The use of molecular oxygen as a spin trap in rigid glassy hydrocarbon media at 77 K is investigated. By slight warming of the matrix, oxygen is found to effectively scavenge the isolated alkyl radicals produced by γ-irradiation to give RO2•, but does not react with radical pairs lying in the ionization tracks. The yield of scavengable radicals in 3MP is determined and compared to the findings of other workers. The butyl radical yields for γ-irradiated 1.0 mol l−1 butyl chlorides in 3MP are found to be: t-BuCl, 5.8; i-BuCl, 5.1; 2-BuCl, 4.9; and 1-BuCl, 2.2. Alkyl radicals cannot be recovered from either RO2 or BuO2 by uv photolysis due to solvent abstraction reactions, or because of photon induced reactions of the alkyl radicals. Photolysis of the butyl radicals themselves at 253.7 nm give rise to decomposition and solvent abstraction reactions.