Sulphur halides

A. Amino-derivatives.—The reactions of sulphur halides with the mono-amino-derivative, NaPgFs NHa, have been described in which the phos-phazene ring stays intact despite very forcing conditions ... 

Comparatively little kinetic work has been done on the halides of sulphur. As in the case of the nitrogen, the greatest attention has been given to the fluorides, and kinetic studies of SF6 and S2F10 are reported below. At the time of writing no other sulphur halides have been investigated in sufficient detail to warrant... 

Halogenation in the presence of sulphur, or by means of sulphur halides, is also available. When chlorine is conducted into a mixture of vanadium pentoxide and sulphur, or when powdered vanadium pentoxide is treated with sulphur monochloride vapours, an immediate reaction sets in, with formation of vanadium oxytrichloride.2 A quantitative yield of this compound is also obtained when vanadium trichloride is heated in oxygen at 500° to 600° C.3... 

A selection of the most important halides is show in the following table. With sulphur the fluorides are most stable and numerous, but Se and Te show an increasing range of heavier halides. Compounds such as S2C12 and S2F10 have S S bonds S2F2 has another isomer S = SF2. Sulphur halides are molecular and monomeric with structures expected from VSEPR (e.g., SF4 see-saw, SF6 octahedral). 

A series of cyclic sulphides is produced in reactions of fluoroalkenes and fluoroalkynes with sulphur or sulphur halides [234-238] some examples have been discussed in Chapter 7 (Figure 8.83). 

Sulphur halides and dialkyl disulphides have been used to obtain a variety of aryithk) and alkytthio derivatives of phenols generally by electrophilic substitution. For example, phenol was treated with zirconium tetrachloride, heated to 156°C under nitrogen, kept at this temperature overnight and after reduction of this to 100°C, diethyidisulphide was added. The mixture was heated to remove ethanethiol and the product, 2-(ethylthio)phenol, isolated in 41% yield (ref. 116). 

Unsaturated Sulphides.—Well-established preparative methods are illustrated in recent work, particularly the use of acetylenes and simple sulphur halides, or thiols, or disulphides. 

Arsenic and antimony show a fairly strong affinity for sulphur. Halides RMCI2 (M = As, Sb) react with H S or NaSH to give oligomeric sulphides (RMS) and with thiols to yield RM(SR )2. Dithiols afford stable and relatively harmless products. This property was used to combat the notorious Lewisite. 

Na COj and Na2S with SO2 or from Na2S03 plus sulphur. Forms many hydrates. Used-in photography ( hypo ) because it dissolves silver halides. Also used in tanning, preparation of mordants, as a fermentation preventative in dyeing and in chemical manufacture. 

Sulphur monochloride, S2CI2, m.p. —80 C, b.p. I38"C. Yellow liquid hydrolysed by water to SO2, HCl and S. Lower halides S CIj (jt up to 5) are formed S2CI2 plus H2 at a hot surface with freezing of products. S2CI2 is used in the rubber industry as a solvent for S. 

Sulphur(Vl) forms the oxide chloride S02C12, sulphuryl chloride see sulphuryl halides). 

Oxygen halides are dealt with in Chapter 11, p. 334. Sulphur, selenium and tellurium form many halides, and only a brief introduction to the subject is given here. 

A number of halide oxides are formed by sulphur and selenium but only one is considered here. 

Chlorine, bromine and iodine form halic(V) acids but only iodic(V) acid, HIO3, can be isolated. Solutions of the chloric) V) and bromic) V) acids can be prepared by the addition of dilute sulphuric acid to barium chlorate(V) and bromate(V) respectively, and then filtering (cf. the preparation of hydrogen peroxide). These two acids can also be prepared by decomposing the corresponding halic(I) acids, but in this case the halide ion is also present in the solution. 

Nickel forms yellow anhydrous halides NiXjlX = F. Cl. Br) and a black iodide Nil2 all these halides are made by direct combination of the elements, and the chloride by reaction of sulphur dichloride oxide with the hydrated salt. All dissolve in water to give green solutions from which the hydrates can be crystallised the solutions contain the ion [NifHjOls], and the chloride crystallises as NiCl2.6H2O, nickel(II) chloride hexahydrate. 

To determine which halogen is present, take 1-2 ml. of the filtrate from the sodium fusion, and add dilute sulphuric acid until just acid to litmus. Add about 1 ml. of benzene and then about 1 ml. of chlorine water and shake. A yellowish-brown colour in the benzene indicates bromine, and a violet colour iodine. If neither colour appears, the halogen is chlorine. The result may be confirmed by testing the solubility of the silver halide (free from cyanide) in dilute ammonia solution silver chloride is readily soluble, whereas the bromide dissolves with difficulty, and the iodide not at all. 

Cold concentrated sulphuric acid will remove unsaturated hydrocarbons present in saturated hydrocarbons, or alcohols and ethers present in alkyl halides. In the former case soluble sulphonated products are formed, whilst in the latter case alkyl hydrogen sulphates or addition complexes, that are soluble in the concentrated acid, are produced. 

If only the monocarboxybc acid is required, the ester after hydrolysis with potash may be strongly acidified with sulphuric acid and the mixture heated under reflux the mineral acid promotes decarboxylation at a temperature just above 100°. The net result is the replacement of the halogen atom of the alkyl halide by —CH COOH thus in the above example ... 

Mercaptans (or thio-alcohols or thiols), the sulphur analogues of the alcohols, were formerly prepared by the interaction of an alkyl halide and sodium hydrosulphide in alcoholic solution ... 

The alkyl sulphides or thioethers, the sulphur analogues of the ethers, are conveniently obtained by boiling alkyl halides with anhydrous sodium sulphide in alcoholic solution, for example ... 

Sulphur, as sulphide ion, is detected by precipitation as black lead sulphide with lead acetate solution and acetic acid or with sodium plumbite solution (an alkaLine solution of lead acetate). Halogens are detected as the characteristic silver halides by the addition of silver nitrate solution and dilute nitric acid the interfering influence of sulphide and cyanide ions in the latter tests are discussed under the individual elements. 

The presence of a halogen may indicate a haloid salt of a base, alky-l, alkylcue, or aryl halide, add halide, haloid derivative of an aldehyde or aad. Some substances, like mustard oils, amino- uilphonic atids and thioamides, contain both nitiogen and sulphur. 

Sulfur oxides produce sulphurous/sulfuric acid. Because oxygen and halides are often also present, high-nickel alloys are required. 

---