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

Abstract

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.

Electron spin resonance studies of the photolysis and radiolysis of O,O′-dialkyl hydrogen phosphorodithioates [(RO)2P(S)SH], their salts, corresponding disulphides, and related compounds: formation of thio and dithio radicals, radical ions, and phosphorus-centred radicals

“…(EtO)#SMe], C12(0R)PO-', and (MeO),P(S-)Br, respectively] and on the similar but clearer spectra obtained from analogous salts (see e.g. Figure 7): radicals of type (10) and (11) are subsequently referred to as of 'PL3 and 'PL,-type for brevity. Further structural and mechanistic details are discussed in a later section.…”

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

“…Both 2-BuC1 and 2-MTHF are considerably more polar than 3MP and may not support selfassociation of thiols to the extent that 3MP does. The presence of thiol diniers has already been established in the uv photolytic studies of the 3MP glass at the same solute concentratio11 (7). In that instance, both the thiyl radical RS.…”

“…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.…”

“…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.…”

“…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.…”