Anions sulphide

Tin disulphide has the same dangerous reactions as sulphides, for which sulphide anion is very sensitive to the effect of oxidants. So the effect of chloric acid and chlorates gives rise respectively to violent detonations and the formation of spectacular showers of sparks. Dichlorine oxide detonates, but this is to be expected. 

The softer electronic character of the thiolate and sulphide anions, compared with the hydroxide ion, results in their greater ability to form ion-pairs with quaternary ammonium cations and, hence, their more efficient transfer into organic solvents. 

In contrast with the reactions involving sulphide or hydrogen sulphide anions, aryl alkyl thioethers and unsymmetrical dialkyl thioethers (Table 4.3) are obtained conveniently by the analogous nucleophilic substitution reactions between haloalkanes and aryl or alkylthiols under mildly basic conditions in the presence of a quaternary ammonium salt [9-15] or polymer-supported quaternary ammonium salt [16]. Dimethyl carbonate is a very effective agent in the formation of methyl thioethers (4.1.4.B) [17]. 

Thiols can be prepared by the action of alkyl halides with an excess of KOH and hydrogen sulphide. It is an SN2 reaction and involves the generation of a hydrogen sulphide anion (HS ) as nucleophile. In this reaction, there is the possibility of the product being ionised and reacting with a second molecule of alkyl halide to produce a thioether (RSR) as a by-product. An excess of hydrogen sulphide is normally used to avoid this problem. 

After an introductory discussion of such misfit structures, various terms that have previously been applied are reviewed, and degrees of incommensurability are used as the basis for a systematic nomenclature. The known structures of specific examples are then discussed graphite intercalates minerals with brudte-like layers as one component (koenenite, valleriite, tochilinites) silicates heavy metal sulphides (cylindrite, incaite, franckeite, cannizzarite, lengenbachite, lanthanum-chromium sulphide) anion-excess, fluorite-related yttrium oxy-fluorides and related compounds. 

Many metalliferous mineral deposits formed at depth are in the reduced state. Where they interface with the near-surface oxidising environment, there is considerable chemical reactivity. This typically takes the form of sulphide oxidation, which includes the generation of several meta-stable sulphur gases that have been shown to be useful in mineral exploration (Chapter 8). Incompletely oxidised sulphide anions and compounds are transported away from mineral deposits at depth by the groundwater, and can be mapped at surface as dispersion patterns of HjS (Chapter 9). 

During the formation of a sulphide mineral deposit there is usually the development of a primary sulphide halo in the host rock. Subsequent to ore formation, sulphide anions and compounds may be dispersed in the aqueous phase in groundwater and the gas phase in air-filled pore spaces to form secondary dispersion patterns. In exploration for sulphide mineral deposits, the simple determination of mobile sulphur species originating from sulphide ore deposits has a clear attraction. In order to understand the way in which such sulphur species occur in soils, a number of in-vitro experiments were performed. On the basis of the results, suitable methods of sampling and analysis have been chosen and tested in soils overlying 30 different mineral deposits. 

The slow (rather than rapid) coloration of the suspended paper is consistent with the slow rate for the above reaction. For the lead acetate paper in contact with the warmed solutions, that in the more oxidising solution was coloured only slightly while that in the more reducing solution was extensively coloured. These results indicate the presence of sulphide anions and/or compounds in both bottles, but in amounts inversely proportional to the Eh of the solutions. 

From this experiment it can be inferred that, in the vicinity of oxidising sulphides, sulphide anions and/or compounds occur mainly in reducing solutions. Only very small amounts of H2S occur in the gas phase, even over solutions of low Eh. Near to the point of oxidation, COS is formed. These findings confirm that, in moist soils, any H2S will be in solution and thus gas-phase migration of H2S will not be possible. 

The experimental investigations show that H2S does not migrate in the gas phase through soil. However, it migrates through water-saturated soil, probably in solution as sulphide anions and compounds. These are subsequently adsorbed onto soil particles, from which they can be released as H2S. This can be determined in concentrations as low as 0.01 mg using lead acetate paper. 

Two methods have been devised for the detection of the dispersion patterns of sulphide anions and compounds in soil (a) the shallow hole method and (b) the container method. In the first method, a 18 mm diameter steel rod is driven into the soil to make a hole that acts as the sample container. After the rod has punched a hole in the soil, it is removed and a device comprising an acid sprayer and gas extraction tube is inserted. (Fig. 9-3). The spray head must be at least 40 cm below the surface and the mouth of the hole must be thoroughly sealed by the spray device. Then the outlet tap of the spray reservoir is opened to allow 8 ml of 30% HCl to reach the spray head and to spray onto the walls of the hole below 40 cm... 

Surveys for dispersion patterns of sulphide anions and compounds determined as acid-released HjS in soil have been carried out over 30 mineral deposits in China, including skams, porphyry copper deposits and porphyritic iron deposits (sulphur contents higher at the margin of the ore body), altered-brecciated gold deposits and lead-zinc deposits in volcanic breccia. Three successful case histories are summarised here. Of the remainder, only four failed to yield anomalies over mineralisation. 

The immediate source of acid-released H2S in soil is sulphide anions, for example,, HS, Me(HS)n , and/or mobile sulphur compounds, such as HjS, COS, CSj. At depth, circulating groundwater provides a medium through which sulphide anions are readily transported in aqueous solution. The results of in-vitro experiments indicate that, in the open pore spaces of overburden and soil, it is unlikely that H2S exists in the gas phase. This and the other sulphur gases are discussed further in Chapter 8. 

A method for detecting sulphide anions and compounds as acid-released H2S has been shown to yield good-contrast anomalies in soils overlying mineral deposits. Satisfactory results have been obtained in different overburden materials of varying thickness, under which mineral deposits are concealed at considerable depths. The equipment and procedure for measuring acid-released H2S in soil are simple, rapid and efficient, can be widely used and are easily adapted. 

Deprotonation of benzylthiotrimethylsilane using r-BuLi induces a Wittig-type rearrangement to the more stable sulphide anion (equation 22). The carbanion generated from methylthiotrimethylsilane behaves similarly, and derivatives can be readily obtained. Thus the protic derivative readily reverts to the thermodynamically more stable thiosilane on heating or under free radical conditions (e.g., with azo isobutyronitrile (AIBN)), but in the presence of base remains as the more stable sulphide anion rather than as a carbanion18. 

Sigmatropic rearrangements of allyl sulphonium allyl ylides (75) provide the basis of a repetitive one-pot ring-expansion sequence" for 2-vinyl thiocyclic compounds (Scheme 50). A paper" and a section in a review article" have described the utilization of allyl thiol dianions and allyl sulphide anions in carbonyl group umpolung . 

Pentafluoro- and pentachloro-benzenethiols can readily be prepared by the reaction of a hydrogen sulphide anion, SH , with hexafluoro- and hexachlorobenzene respectively . No dithiols can be produced in this reaction. Due to the basic medium employed the thiol formed will be present as its thiolate anion, which is not readily attacked further nucleophilically. Using hexafluorobenzene and excess hydrogen sulphide perfluoropoly(phenylene sulphide) may be isolated . When the hydrogen sulphide anion is replaced by a thiolate as a nucleophile, multiple replacement of fluorine or chlorine can occur. The products of these reactions can be summarized ... 

Recent examples of the application of isothiocyanates in the synthesis of dithiocarbamates include the synthesis of butyl diphenylphosphinyldithio-carbamate by the reaction of diphenylphosphinyl isothiocyanate with sodium butylmercaptide, the synthesis of methyl diethoxyphosphinyldi-thiocarbamate by the successive treatment of diethylphosphoryl isothiocyanate with hydrogen sulphide anions and methyl iodide, and the reaction between phenyl isothiocyanate and butyl dibutylthioboronite to afford the 1 1 adduct (321), which on hydrolysis is converted into butyl iV-phenyl-dithiocarbamate. The action of hydrogen sulphide on l,4-dicyanato-2,5-... 

Besides reacting with halide, as shown above, the poly sulphide anions are continually interchanging with the polysulphide groups present in the polymeric product, e.g. ... 

The physico-chemical properties of the iron sulphide film can control the impact of sulphides on the steel dissolution, whereas these impacts and effects themselves are dependent on the ferrous ion/sulphide anions ratio, the presence of SRB and how the biofilm has covered the metal surface. ... 

The thiocarbonyl sulphur atom has been introduced into several cyclic thioamides by the reaction of the appropriate cyclic chloro-imines with nucleophiles such as thiourea " and the hydrogen sulphide anion. - Some selenopyrrolones (212) have been prepared from the corresponding 3-formyl-2-chloropyrrole by successive treatment of the latter with potassium hydrogen selenide and secondary amines. A reinvestigation of the... 

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