(1R,3S)1,3-dibromocyclopentane (or 1s,3r?) and 1,1-dibromocyclopentane both have internal planes of symmetry but why is only the first one a meso compound?

1 Answer
Jul 1, 2018

Because by definition, a meso compound contains TWO potential chiral centres..

Explanation:

And of course a meso compound is an RS compound, such that it contains an internal plane of symmetry. And the goto example is dimethylene glycol, i.e. H3C.CH(OH).CH(OH)CH3...the chiral centres are indicated.

Now such a structure gives rise to TWO enantiomers, i.e. RR, and SS...and the RS meso structure...i.e. here RSSR...

For 1,1Br2C5H8...THERE IS NO GEOMETRIC/STEREOCHEMICAL dimension to the structure. And certainly its mirror-images are superposable...