Sulfur atoms, reactions

Thus, the eventual products of the two pathways (la) and (lb) by which OH reacts with DMS under atmospheric conditions have not yet been fully established. However, circumstantial evidence, namely the 70% yield of SO2 in the study of Barnes et al. (21) being roughly equal to the branching ratio for the H-atom abstraction (reaction (la)) at 298 K determined by Hynes et al. (12), indicates that S02 is a major product of the abstraction reaction and that DMSO, DMSO and MSA probably result from the primary addition of OH to the sulfur atom (reaction (lb)). 

In almost all of the gas-phase kinetic-mechanistic studies on sulfur atom reactions made to date, the source has been the in situ photolysis of carbonyl sulfide (COS). The reasons for this choice are not far to seek. Carbonyl sulfide is a stable, readily available gas. Its absorption spectrum is located in a convenient spectral region and the carbon monoxide formed in the photodissociation provides an excellent internal monitor for sulfur atom production. 

The Benson mechanism can in principle be extended without major modifications to insertion reactions of other divalent species, such as oxygen and sulfur atoms. With oxygen, Yamaaaki and Cvetanovid have shown recently that 0( Z>) atoms preferentially insert, while 0( P) atoms abstract. This despite the fact that the singlet state hes some 48 kcal./ mole above the ground triplet state. On the other hand, sulfur atom reactions seem compatible with the proposed mechanism. Thus, if one attempts to apply it for the insertion of S( D) atoms, one finds that its predictions are consistent with the experimentally observed trend in the reaction rates. Here the transition state, due to the ionization potential and electron affinity of S( Z)) atoms being higher than those of alkyl radicals (9.2 and 2.2 e.v., respectively) could be formulated as... 

That the mercaptan product arises exclusively from singlet sulfur atom reactions was proven in experiments with added CO2. The data in Table VI clearly demonstrate the suppressing effect of COj on the mercaptan yield, with a concomitant and equivalent rise in episulfide production. Further substantiation comes from mercury-photosensitization studies with COS in which it was found that the sulfur atoms produced by this means yield only episulfide, no mercaptans being formed with ethylene or with any of the other olefins studied. 

In order to make this article on sulfur atom reactions as complete as possible, the authors have included a great many recent data from the Photochemistry Laboratory at the University of Alberta. We would like to express our deep appreciation to the following members of the Photochemistry Laboratory who have kindly consented to allow us to use their yet unpublished work ... 

Thiocarbonyl compounds are also substrates of monooxygenases, forming S-monoxides (sulfmes, reaction 3-A) and then S-dioxides (sulfenes, reaction 3-C). Asa rule, these metabolites cannot be identified as such because of their reactivity. Thus, S-monoxides rearrange to the correspondingcarbonyl by expellinga sulfur atom (reaction 3-D). This reaction is known as oxidative desulfurationand occurs in thioam-ides and thioureas (e.g., thiopental). As for the... 

Qulfur atoms and the atoms of the group Via elements undergo facile addition to olefins and acetylenes. These reactions represent the simplest examples of a cycloaddition reaction. Among them, the sulfur atom reactions stand out with their experimental simplicity, cleanliness, and unique reactivity. Therefore the sulfur atom-olefin system is a model for studying some of the little explored aspects of cycloaddition reactions. Since the first report on sulfur atom addition reactions which appeared in 1962, a considerable amount of quantitative data and relevant information have accumulated on the subject, which are summarized briefiy here. 

Possible reactions of hydrogen sulfide with nickel can have different natures formation of bulk nickel sulfides via chemical reactions, reaction (5.7) surface sulfuration either via physical adsorptions of hydrogen sulfide molecules, reaction (5.8), or via chanisorptions of sulfur atoms, reaction (5.9) [18]. 

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