Chalcogen hydrogen sulfide

Sulfur is a tasteless, odorless, nonmetallic element. Sulfur along with selenium (Se) and tellurium (Te) are called chalcogens. The valences of sulfur are 2, 4, and 6, which can be represented by compounds such as hydrogen sulfide (H2S), sulfur dioxide (SO2), and barium sulfate (BaS04), respectively. Pure sulfur is insoluble in water. The most stable variety of sulfur, rhombic sulfur, is a yellow crystalline solid. 

Reduced chalcogens. The sulfide ion, in moderately to strongly alkaline solution, precipitates Ca " as white, granular CaS [not Ca(OH)2 as sometimes claimed]. Hydrogen sulfide dissolves CaS, forming Ca and HS . Alkali sulfides precipitate Sr possibly as Sr(HS)2, white, from solutions not too dilute. Solutions of Ba treated with an alkaline sulfide give a white precipitate, possibly Ba(HS)2. 

Tertiary phosphine sulfides are generally stable compounds and are not easily oxidised by air, although they can be oxidised by hydrogen peroxide or dilute nitric acid. The analogous tertiary phosphine selenides and tellurides are however, more reactive to oxidation. Similar to the sulfides they can be prepared from the direct reaction of elemental chalcogen with a tertiary phosphine (Equation 1). Tertiary phosphine selenides are also accessible from tertiary phosphines using KSeCN as the selenium source instead of the element itself. 

A number of cyclopropyl sulfides have been prepared from other cyclopropanes by reactions involving cleavage of a bond from one of the cyclopropyl carbons to hydrogen, halogens, and, in a few cases, a chalcogen moiety. 

PTN(Me) is a white microcrystalline material, which is air stable in the solid state. The corresponding oxide cannot be obtained by classical P-phosphine oxidation with hydrogen peroxide, while the sulfide and selenide derivatives are easily and quantitatively prepared by reaction with the appropriate chalcogen element.6 PTN (Me) is soluble in nonpolar and polar solvents including water. At 20°C, PTN(Me), 1.18 g dissolves in 1 mL of water (6.81 x 10 2M). 

The metal precursor is generally the ion, whereas the chalcogenide precursor can be thiosulfate (S2O] ) [25], selenosulfate (SSeO] ) [51], or HTeOJ [24] for sulfides, selenides, and tellurides, respectively. In the case of oxides such as ZnO, the chalcogen precursor can be molecular oxygen or hydrogen peroxide [13]. II-VI compounds have also been synthesized electrochemicaUy from non-aqueous organic solvents [52, 53] and from ionic Hquids [54]. II-VI compounds have also been synthesized by ECALE [22, 55], but this process is not suited for large-scale fabrication. 

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