Dimethyl disulphide

Mixtures of dimethyl sulphide and oxygen explode with a blue flash at 210 °C [109]. Sulphur is deposited, and other products include sulphur dioxide, carbon monoxide, carbon dioxide, methane and methane thiol but methanol and dimethyl disulphide were not found. 

Below this temperature, the pressure—time curves are S-shaped and the stoichiometry of the reaction is represented by [110] 

The rate of reaction (after the induction period) is linearly dependent on the initial oxygen pressure, but substantially independent of the initial sulphide pressure. The reaction is inhibited by sulphur dioxide, and ceases before all the reactants are consumed. 

Harkness and Murray [109], while agreeing that in slow combustion all the sulphur is converted to sulphur dioxide, failed to find methanol. Carbon dioxide and methane were also absent, but a little formaldehyde was present in the products. 

The combustion of diethyl sulphide proceeds explosively at 170 °C whereas at 155 °C the reaction is very quickly self-inhibited. Analytical studies using a packed vessel at 195 °C showed that the products were sulphur dioxide, acetaldehyde, acetic acid and water [110]. 

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Smith NA, DP Kelly (1988) Isolation and physiological characterization of autotrophic sulphur bacteria oxidizing dimethyl disulphide as sole source of energy. J Gen Microbiol 134 1407-1417. 

In a related paper, reaction of(60a) with (56) gave the hydrospirophosphorane (61) which upon u.v. irradiation in the presence of dimethyl disulphide gave the methylthio derivative (62) which was also prepared by the reaction of(60b) with hexafluoroacetone1 2. In contrast, the reaction of (63) with hexafluoro-acetone furnished a 1 1 mixture of the 1,3,2-A3- and 1,3,4-A5-dioxaphospholanes (64) and (65). 

Still another related method consists in reacting dienes with dimethyl disulphide in the presence of iodine, to produce the corresponding bis(o ,/J-dmiethylmercapto) derivative241-243. Again, characteristic fragmentation is obtained in the standard El spectra. However, this method involves complications if the double bonds are separated by less than four methylene groups due to the formation of cyclic thioethers. 

Fig 7. Trace of sulphur containing volatiles in pig slurry headspace, a hydrogen sulphide b carbon disulphide c dimethyl sulphide d dimethyl disulphide... 

The only odour-intensive species conclusively identified in the odorous emission of water reclamation works were dimethyl -disulphide, -trisulphide and -tetrasulphide. 

Brandsma and coworkers were able to show that meta- (59a) and para-dilithiated benzene (59b) are accessible via iodine-lithium exchange, using n-butyllithium. Therefore, 1,3- and 1,4-diiodobenzene (58a and 58b) respectively were reacted with two equivalents of n-butyllithium in diethyl ether at low temperatures (Scheme 21). The polyUthiation was confirmed by trapping reactions with dimethyl disulphide. The same reactions, starting from the corresponding dibromobenzenes, had led only to monolithiated benzenes. 

Many cheeses contain the same or similar compounds but at different concentrations and proportions chromatograms of some cheese varieties are shown in Figure 10.25. The principal classes of components present are aldehydes, ketones, acids, amines, lactones, esters, hydrocarbons and sulphur compounds the latter, e.g. H2S, methanethiol (CH3SH), dimethyl sulphide (H3C-S-CH3) and dimethyl disulphide (H3C-S-S-CH3), are considered to be particularly important in Cheddar cheese. The biogenesis of flavour compounds has been reviewed by Fox et al. (1993, 1996a) and Fox, Singh and McSweeney (1995). 

There is no need to isolate this compound in order to effect addition of diphenyl disulphide (and dimethyl disulphide) to alkenes in this way tran. -l,2-bis-phe-nylthio (and methylthio) adducts were formed from cycloalkenes and 1-hexene. 

On the other hand, methanethiol can be oxidised to dimethyl disulphide (that has a perception threshold in the air seven times weaker than hydrogen sulphide. 

Methane thiol oxidizes at a convenient rate at 200—275 °C, the reaction being mildly autocatalytic and accompanied by a pressure decrease [107]. The rate is enhanced by increased oxygen concentration, but retarded by excess thiol. The main products include sulphur dioxide, carbon monoxide, formaldehyde, acetaldehyde and methane but no hydrogen sulphide, carbonyl sulphide or free sulphur. Unless excess oxygen is present, these products do not account for all the sulphur consumed, and Cullis and Roselaar [107] attributed this to formation of dimethyl disulphide although later work [108] has shown that this explanation was unlikely. 

The combustion of dimethyl disulphide was studied at 240 °C. The reaction is autocatalytic, the principal products being sulphur dioxide, methanol and carbon monoxide with smaller amounts of formaldehyde, methane thiol and an acid [111]. 

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