Question

The process of separating a racemic mixture into optically pure (+) and (−) enantiomers is known as:
(A) mutarotation
(B) epimerization
(C) asymmetric synthesis
(D) resolution

Answer 1

Hint : A racemic mixture, also known as a racemate, is a chiral molecule that contains equal amounts of left- and right-handed enantiomers. Racemic acid, discovered by Louis Pasteur to be a mixture of the two enantiomeric isomers of tartaric acid, was the first known racemic mixture. An enantiomerically pure or enantiopure compound has only one enantiomer.

Complete Step By Step Answer:
A racemate is optically inactive, which means that no net rotation of plane-polarized light occurs. Even though the two enantiomers rotate plane-polarized light in opposite directions, the rotations cancel because they are present in equal amounts.
In contrast to the two pure enantiomers, which have identical physical properties except for the rotational direction of plane-polarized light, a racemate can have properties that differ from either of the pure enantiomers. Different melting points are most commonly encountered, but different solubilities and boiling points are also possible.
Enantiomers are molecules that exist in two forms that are mirror images of one another but cannot be superimposed. Enantiomers are chemically identical in every other way.
Option A: mutarotation: Mutarotation is the change in optical rotation caused by a change in the equilibrium between two anomers when their stereocenters interconvert. Mutarotation occurs in cyclic sugars when the anomeric forms interconvert.
Option B: epimerization: An epimer is one of two diastereomers in stereochemistry. Only one stereogenic center out of at least two has an opposite configuration for the two epimers. Every other stereogenic center in the molecules is the same. The interconversion of one epimer to the other epimer is known as epimerization.
Option C: asymmetric synthesis: Asymmetric synthesis refers to any chemical reaction that alters the structural symmetry of a compound's molecules, converting the compound into unequal proportions of compounds that differ in the dissymmetry of their structures at the affected center.
Option D: resolution: In chemistry, resolution refers to any process that separates a racemic mixture into its two constituent enantiomers. It is also known as optical resolution or chiral resolution. (Enantiomers are substances that have dissymmetric atoms and structure arrangements that are nonsuperimposable mirror images of one another.) Louis Pasteur used two important methods of resolution.
Resolution refers to the process of separating a racemic mixture into optically pure (+) and (-) enantiomers. It can be accomplished through
It can be accomplished through
(a) mechanical separation,
(b) reaction with enzymes,
(c) formation of diastereomers, and
(d) chromatography.
**Thus, the answer is option D: resolution.
Note :
Resolution is extremely difficult because enantiomers have identical physical properties such as solubility and melting point. Diastereomers, on the other hand, have different physical properties, which are used to resolve racemates. When a racemate reacts with an enantiomerically pure chiral reagent, it produces a mixture of diastereomers that can be separated. Reversing the first reaction then leads to the separated enantiomers plus the recovered reagent.