1)We know that geometrical isomers are exhibited by alkenes and not by alkanes.It is because of the fact that alkanes undergo rotation along the sigma bond.This ability is also responsible for the existence of conformers.
But if alkanes can undergo rotation why do meso compounds and D/L enantiomers exist.They should be readily interconvertable.
262conformers of the same compound have the same optical activity.
rotation about a C-C single bond does not change a compound from D to L (or vice versa)
if you have done R-S nomenclature for compounds in sawhorse projection you should be very clear with this concept.
71Yes, Bond rotation won't change the priotity and hence the absolute Configuration of the carbon centers. You know that two enantiomers don't have the same configurations at atleast one carbon.
21To rephrase my question with an example consider tartaric acid.
Tartaric acid exist in both meso and enantiomeric form(d or l).
If it can rotate along the sigma bond between the 2 chiral carbons.Then optically inactive meso comp. should be converted to optically active d/l form readily.
Then why does it show optical inactivity or vice versa.
71It might look like, but the orientation of the groups attached to those carbon won't be same as in meso and optically active form.
You may try some 3D models on google.