The stereochemistry of molecules and ions containing S chains

Since the stereochemistry of a molecule S 2R2 is similar to that of a sulphur chain S the following remarks apply equally to three main groups of compounds molecules S 2R2, polysulphide ions S , polythionate ions S Og and closely related molecules such as TeS i04R2. 

The stereochemistry of azo compounds, RN=NR, is similar to that of, for example, dihalogenoethylenes, the compounds existing in planar cis and trans forms  

The two forms of a molecule R1SSR2, on the other hand, differ in having R2 on different sides of the plane SSRi  

Although they appear to correspond to the cis and trans isomers of an azo compound they are in fact d and / enantiomorphs. Examples include S2H2, S2F2, and S2CI2, in all of which the dihedral angle is close to 90°. 

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