Question 44

[Guest]

how are 1 and 2 meso compounds???thanks

[admin]

In order to see how 1 and 2 become meso: (1) remember that the question says that the C=O group at the top will be oxidized to -COOH (same group at the "bottom" of the molecule in the diagram); (2) keep in mind the definition of a meso compound:

[admin]

bump

[sbains3528]

If 1 and 2 become COOH groups why don't 3 and 4?

[mohsinalam5969]

A meso compound or meso isomer is a chemical compound with molecules that contain 2 or more asymmetric atoms (stereocenters) but which is optically inactive (or achiral) because it contains an internal plane of symmetry.
Also a meso compound or meso isomer is a non-optically active member of a set of stereoisomers, at least two of which are optically active. This means that despite containing two or more stereocenters (chiral centers) it is not chiral. A meso compound is superposable on its mirror image, and it does not produce a "(+)" or "(-)" reading when analyzed with a polarimeter.presence of chiral centre is not compulsory for mesocompounds.
After such oxidation, compounds 1 and 2 become meso compounds and thus non-chiral. Thus they lose their optical activity. However, compounds 3 and 4, after such an oxidation, are still chiral and therefore optically active.

[sanji2896161]

[mananbhatt3019]

3 and 4's COH's are oxidized to COOH's as well. They are optically active though. If you draw the Fischer projection of the mirror image of either 3 or 4, there is no way to rotate the projection so that it matches the original compound. Thus, they are enantiomers.