Sulphur transformations

The properties of a material must dictate the applications in which it will best perform its intended use. All materials made to date with polymerized sulphur show time-dependent stress-strain behaviour. The reversion to the brittle behaviour of orthorhombic sulphur is inevitable as the sulphur transforms from the metastable polymeric forms to the thermodynamically stable crystalline structure. The time-span involved of at most 15 months (to date) would indicate that no such materials should be used in applications dependent on the strain softening behaviour. Design should not be based on the stress-strain relationships observed at an age of a few days. Since the strength of these materials is maintained, however, uses based on strength as the only mechanical criterion would be reasonable. 

Mayer B., Fritz P., and Krouse H. R. (1992) Sulphur isotope discrimination during sulphur transformations in aerated forest soils. In Workshop Proceedings on Sulphur Transformations in Soil Ecosystems (eds. M. J. Hendry and H. R. Krouse). National Hydrology Research Symposium No. II, Saskatoon, Sakatchewan, November 5-7, 1992, pp. I6I-I72. 

Rhombic sulphur transforms to monoclinic sulphur at 95.5°C (368.5 K) with an enthalpy change of 96 cal/mole (401.7 j/mol). Test the validity of the third law of thermodynamics for this transition from the following data ... 

FRENEY J.R. and SWABY R.J. 1975. Sulphur Transformations in Soils. Sulphur in Australasian Agriculture. Ed. McLachlan K. Sydney University Press. 

Pinacol upon dehydration with acid catalysts e.g., by distillation from 6A sulphuric acid or upon refluxing for 3—4 hours with 50 per cent, phosphoric acid or hydrated oxalic acid) is transformed into methyl ter<.-butyr ketone or plnacolone ... 

The following are examples of the above procedure. A mixture of diethylamine and re-butyl alcohol may be separated by adding sufficient dilute sulphuric acid to neutralise the base steam distillation will remove the alcohol. The amine can be recovered by adding sodium hydroxide to the residue and repeating the distillation. A mixture of diethyl ketone and acetic acid may be treated with sufficient dilute sodium hydroxide solution to transform the acid into sodium acetate and distilling the aqueous mixture. The ketone will pass over in the steam and the non-volatile, stable salt will remain in the flask. Acidification with dilute sulphuric acid hberates acetic acid, which can be isolated by steam distillation or by extraction. 

The three alkaloids concerned, morphine, codeine and thebaine, all behave as tertiary bases. Morphine contains two hydroxyl groups of which one is phenolic and the other a secondary alcohol group. On methylation of the phenolic hydroxyl codeine results. On oxidation, codeine is transformed into codeinone by conversion of the secondary alcohol group into a carbonyl group, and when thebaine is boiled with A-sulphuric acid for a few minutes, it is hydrolysed into codeinone and methyl sulphate, and in other ways thebaine has been shown to contain two methoxyl groups. That the relationship between the three alkaloids is close may be illustrated by the following slightly extended formula —... 

Tantalum is severely attacked at ambient temperatures and up to about 100°C in aqueous atmospheric environments in the presence of fluorine and hydrofluoric acids. Flourine, hydrofluoric acid and fluoride salt solutions represent typical aggressive environments in which tantalum corrodes at ambient temperatures. Under exposure to these environments the protective TajOj oxide film is attacked and the metal is transformed from a passive to an active state. The corrosion mechanism of tantalum in these environments is mainly based on dissolution reactions to give fluoro complexes. The composition depends markedly on the conditions. The existence of oxidizing agents such as sulphur trioxide or peroxides in aqueous fluoride environments enhance the corrosion rate of tantalum owing to rapid formation of oxofluoro complexes. 

In the glass-bottle industry the bottles can be cooled in a dilute SOj/SO, atmosphere to increase chemical resistance. A similar effect has been noted with vitreous enamel. It has been postulated that a thin layer of —OH groups or — OH—HjO (hydronium) ions is adsorbed on the surface of a fired enamel. These ions are transformed into — OSO, or —OSO3 in the presence of oxides of sulphur which are more resistant to further acid attack. It is known that the acid resistance of a recently fired enamel improves on ageing, probably due to the enamel reaction with SOj/SO, in the atmosphere and it is quite common for the grading to improve from Class A to Class AA (BS 1344). 

F unctionalization of organic substituents adjacent to the sulphoxide moiety constitutes an important method of the synthesis of a variety of sulphoxides, which are not available by the methods described in the previous sections. Such transformations enable one to synthesize a large number of very sophisticated sulphoxides which are required for special purposes or serve as a source of many sulphur-free organic compounds. 

Atmospheric emissions of sulphur dioxide are either measured or estimated at their source and are thus calculated on a provincial or state basis for both Canada and the United States (Figure 2). While much research and debate continues, computer-based simulation models can use this emission information to provide reasonable estimates of how sulphur dioxide and sulphate (the final oxidized form of sulphur dioxide) are transported, transformed, and deposited via atmospheric air masses to selected regions. Such "source-receptor" models are of varying complexity but all are evaluated on their ability to reproduce the measured pattern of sulphate deposition over a network of acid rain monitoring stations across United States and Canada. In a joint effort of the U.S. Environmental Protection Agency and the Canadian Atmospheric Environment Service, eleven linear-chemistry atmospheric models of sulphur deposition were evaluated using data from 1980. It was found that on an annual basis, all but three models were able to simulate the observed deposition patterns within the uncertainty limits of the observations (22). 

Solid acids can also be prepared from these materials by transformation of the sulphur group to the sulphonic acid, very closely related to sulphuric acid, one of the most commonly used acids industrially. The material can be easily recovered and easily handled since the acidity resides within pores, it cannot come into contact with living tissue. Important transformations, such as the formation of synthetic lubricants and intermediates for fragrances, have already been reported using these materials. The scope for such materials in future is enormous. 

H. W. Hunt, J. A. E. Stewart, and C. V. Cole, Concepts of sulphur, carbon and nitrogen transformations in soil evaluation of simulating modeling. Bioj eochemis-try 2 163 (1986). 

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