Sulphur-halogen compounds

Sulphur-Halogen Compounds.— The available data for the physicochemical and, primarily, chemical properties of SF have been collated in a review. The variation in the melting point of SF with pressure has been calculated by means of the Clausius-Clapeyron equation as 0.08—0.1Katm which has been confirmed by experiment. The reactions of SFg with various container materials have been studied. From analytical results and i.r. absorption frequencies, the 

Marassi, G. Mamantov, and J. Q. Chambers, Inorg. Nuclear Chem. Letters, 1975, 11, 245. 

Ugorets. K. T. Rustembekov. and Y. A. Kushnikov, Tr. Khim.-Metall. Inst., Akad. Nauk 

A complete quantitative estimate of the Sip4 and OF2 content could not be obtained because of secondary reactions. In stainless steel and eopper reaetion tubes, SFf, deeomposed to SF4 and the metal fluoride. Fhermodynamie caleula-tions have shown that at temperatures up to 1500 C SF dissociates principally to SF4 these results therefore lend further support to the calculations. Metal fluorides have also been observed as the products of the exothermic reactions between SF, and some oxides of Group II and Group III elements at 500— 800 °C. 

Several new derivatives of sulphur hexafluoride have been prepared. NSF, reacts with OSF4 to give pentafluorosulphur oxide difluoride imide (2), which hydrolyses with alkali to the ion [F,S—NSO2F] . 

Sulphur-Halogen Compounds.—The chemistry of the lower sulphur fluorides has been reviewed.59 The review, which cites 90 references, places most emphasis on the compounds S2F2, SF2, S2F4, S F2, and RSF. 

The semi-empirical CNDO/2 method has been applied64 to an analysis of the electronic structure and conformation of disulphur decafluoride. The results, in good agreement with the available experimental data, enable the calculation of the electronic terms which determine the shape of the potential surface and a discussion of the electronic non-equivalence of the axial and equatorial fluorine atoms, the chemical bond strength, and the anomalous S—S bond length in the S2F10 molecule. 

A convenient method for the preparation of telomers of pentafluoro-sulphur iodide, with the general formula SF5(C2F4)nI, has been described.69 The compounds were prepared by the reaction of disulphur decafluoride with equimolar amounts of 1,2-di-iodotetrafluoroethylene at 150 °C in an autoclave, with the simultaneous injection of tetrafluoroethylene  

The value of n was found to be a function of the amount of C2F4 injected, and it was possible to obtain the first member of the series, SF5C2F4I, almost exclusively. The reaction  

The oxidation of the compounds SF5(CF2) I, where n = 2 or 4, by C1F3 has been shown70 to yield fluoroalkanes having both SF5 and IF4 or IF2 substituents, the CF2SF5 group being chemically inert. The reaction  

Sulphur-Halogen Compounds.— The reaction of gaseous SFg with carbon in a heated Knudsen cell has been studied by mass spectrometry, and several new molecular species, including SF, SFa, and SCF2, have been identified. Ionization potentials, with an estimated accuracy of 0.10 eV, have been obtained and LHq for the process  

The experimental results for the laser-induced fluorescence of SF, and SFg-rare gas mixtures have been reported. The interaction of SF, with metals and oxides has been studied by thermal analysis techniques. It was shown that SF, is an active fluorinating agent, reacting with oxides at temperatures between 600 and 700 °C and with metals between 500 and 600 °C. 

Oxides were generally converted into fluorides whilst metals gave both IBuorides and sulphides. 

A new species, the chlorodisulphanyl radical (CISS ), has been produced by the photolysis of ClgSg in inert matrices at 4.2 K. The identification of the species rested on the complete simulation of its well-resolved e.s.r. spectrum. 

Equimolar amounts of SClg and SgClg have been shown to react with phenylperthiophosphonic anhydride (13) to yield, quantitatively, bis(phenyl-chlorothiophosphoryl)-tri- (14) and -tetra-sulphane (15), respectively. The 

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Liquid sulphur compounds should be weighed and introduced into the Carius tube by precisely the same methods as those described for liquid halogen compounds (p. 442). 

Air contaminants Gases sulphur oxides, halogen compounds Mists aerosols, salt, alkalies Particulates sand, dust, grease... 

Heating the Tube.—Place the iron case with its tube in a bomb or tube furnace in such a way that the end with the capillary is raised somewhat and directed towards the wall on which a shield is fixed and close the furnace. Several tubes may be heated simultaneously. Light all the burners and heat gradually to the desired temperature, regulating the gas supply at the main tap. For aliphatic halogen compounds (and many sulphur compounds) this temperature is about 250°, for the aromatic compounds (and sul-phonic acids) it is about 300°. Most substances are completely oxidised after three to four hours, but in the case of aromatic compounds the heating is continued for some hours longer. 

The main analytical technique for pesticides is gas chromatography using a variety of detectors such as electron capture for halogenated compounds, thermionic for compounds containing either phosphorus or nitrogen, and flame photometric for compounds containing sulphur or phosphorus. 

The pentavalent halides and oxyhalides, as in the case of other niobium compounds, are the most stable. It is remarkable that the pentavalency is maintained with increase in the atomic weight of the halogen. All the halogen compounds are characterised by their ready tendency to undergo hydrolysis on the addition of water or even in damp air with precipitation of niobie acid and formation of the hydrogen halide. Their preparation can, therefore, be effected only in the dry way (a) synthetically, or (b) by the action of chlorine, carbon tetrachloride, or sulphur monochloride on the oxide or sulphide. They do not possess saline properties, and cannot be prepared by the action of the halogen acids on the oxide. 

Sulphur-Oxygen-Halogen Compounds.—Thionyl fluoride has been shown76 to react with Cl2F+AsF6 at —78 °C to give OSCIFz AsFe in ca. 85% yield ... 

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