Meso compounds are achiral molecules that possess multiple chiral centres. The reason for them being achiral is because they possess an internal plane of symmetry (also known as centre of symmetry). This internal plane of symmetry cause their mirror images to be superimposable.
Meso compound is therefore optically inactive. The optical activity of one half of the meso molecule cancels out the optical activity of the other half of it.
Maximum Possible Number of Enantiomers (Optical Isomers)
Maximum possible number of enantiomers = 2n whereby n is the number of chiral centres in the molecule
Note that the above formula gives the maximum possible number of enantiomers!
To see whether it also gives you the actual number of enantiomers, you need to draw out all the possible isomers and then check whether there are any identical isomers. The identical isomer is known as the meso compound which is optically inactive and will not be considered as an enantiomer (optical isomer).
Let’s take a look at an example to have a clearer picture on finding the actual number of enantiomers.
Number of chiral centres in molecule, n = 2
Maximum possible … Continue reading ...