Do meso compounds have enantiomers? Why or why not?

Question

Do meso compounds have enantiomers?  Why or why not?

Nolan Allen · Accepted Answer

No, a #"meso"# compound is an #RS# species, that is equivalent to the #SR# species.

A #"meso"# compound is a symmetric #RS# species, where the 2 (potentially) chiral centres map onto each other upon inversion. Given that #R,S# #=# #S,R#, these are the same structure, and symmetrically equivalent. Of course, the structure could give rise to #S,S# and #R,R# enantiomers, as well as an equivalent pair of #R,S# and #S, R#. In this case, the former pair, #S,S# and #R,R#, ARE enantiomeric. I strongly advise you to acquire a set of basic models to illustrate isomerism and to practice writing it on paper. Start with #H_3C-CH(OH)CH(OH)CH_3#. This is a simple structure, but will generate a pair of non-superposable enantiomers, and a meso-isomer. I forget its trivial name, but the structure is a favorite for examiners.

Christian Anderson · Answer

undefined Meso compounds do not have enantiomers because they possess an internal plane of symmetry. This internal symmetry divides the molecule into two halves that are mirror images of each other but can be superimposed on each other. As a result, meso compounds are optically inactive and do not exhibit optical isomerism.