A schematic analysis of the reaction of the enantiomer with racemic mixture is shows below:
`{:(d,+,"d and l",rarr,(d)-(d)),("The(+)-form of",,"A racemic mixture of",,+),("chiral molecules",,"other molecules with",,(d)-(l)),(,,50%(d) and 50%(l),,):}`
The products (d-d) and (d-l) are clearly neither identical nor enantiomers (non-superimposable mirror images) as the diastereomers, stereoisomers that are not mirror images' . The formation of diasteromers allows the separation of enantiomers (called resolution) which is not easy as enantiomers have identical physical properties. One general with naturally occurring chiral molecule to form a pair of diastereomers. These can be separated easily as they have different physical properties. If the original chemical reaction can be reversed, the enantiomers can be isolated.
Which of the following is not true ?

Options

A. (a) Diastereomers have different melting points and solubilities in a given solvent.
B. (b) Diasteromers have similar chemical properties.
C. (c) Distereomers are optically active compounds with same or optisite sign of rotaion.
D. (d) Diastereomers differ in adsorption.

Answer

C

Explanation

(a) is true, (b) is true, and (d) is true. (Adsorption is a physical property. So it is different for diastereomers.) (c) is not true.
1. Diastereomers can be optically inactive, e.g., cis-2-butene and trans are geometrical isomers and are diasteromers.
2. Similarly, gauche and anti forms are not optically active and are conformers and diastereomers.