How can it be proved that (S)-bis-[2-(t-butylsulfinyl)phenyl] diselenide is a chiral non-racemic product? I read in paper that:


  The aim of this part of the work was to synthesise new aromatic diselenides with chiral phosphorous or sulfoxide centres in coordinative distance to the selenium as precursors for new chiral selenenylating reagents.


How can it be proved that (S)-bis-[2-(t-butylsulfinyl)phenyl]diselenide is a chiral non-racemic product?
Compounds with the general structure $\ce{R-SO-R'}$, i.e. containing a sulfinyl $\ce{-SO-{}}$ functional group attached to two carbon atoms, are called generically ‘sulfoxides’. Sulfoxides may be considered as a tetrahedral system composed of a central atom, ligands, and a lone pair of electrons (or phantom atom).



When the two organic residues $\ce{R}$ and $\ce{R'}$ are dissimilar, the sulfur atom is a stereogenic center.

The compound bis[2-(tert-butylsulfinyl)phenyl]diselenide contains two chiral sulfinyl groups and thus two stereogenic centers.



Therefore, three stereoisomers exist:


bis[2-((R)-tert-butylsulfinyl)phenyl]diselenide,  


bis[2-((S)-tert-butylsulfinyl)phenyl]diselenide,  


and the meso compound [2-((R)-tert-butylsulfinyl)phenyl][2-((S)-tert-butylsulfinyl)phenyl]diselenide