Group 13 sulfides hydrogen selenide

The biosynthesis of the seleno amino acids is not fully understood. It seems, however, that selenite and selenate are reduced to hydrogen selenide, which reacts with L-serine or L-homoserine as described for hydrogen sulfide (Dll and D 12). L-Methylselenocysteine and L-selenomethionine may be formed by methyl group transfer. 

Determine the point groups of the following molecules. (a) Hydrogen selenide, H2Se (b) Partially deuterated hydrogen sulfide, or HDS (c) The chair conformer of cyclohexane, CgH,2 (d) The boat conformer of cyclohexane, CgH,2... 

Very little is known about chalcogenide halides of Group IVB elements. Although the existence of sulfide chlorides (45, 274, 329, 365) and of a selenide chloride (329) of titanium was claimed in early publications, their true composition, and even their existence, remains doubtful. They have usually been obtained by the reaction of titanium chlorides with sulfur and selenium, respectively, or with hydrogen sulfide. The synthesis of a pure compound, TiSClj, was published in 1959 (113). It is an intermediate of the reaction of TiCU with HjS. 

Aqueous solutions of hydrogen sulfide, selenide, and telluride are acidic acid strength increases as the group is descended H2S < H2Se < H2Te. The same trend was observed for increasing acidity of the hydrogen halides. The acid ionization constants are... 

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