Question: 74: The incorrect statement regarding chirality is
(1) Enantiomers are superimposable mirror images on each other
(2) A racemic mixture shows zero optical rotation
(3) \mathrm{S}_{\mathrm{N}}1 reaction yields 1:1 mixture of both enantiomers
(4) The product obtained by \mathrm{S}_{\mathrm{N}}2 reaction of haloalkane having chirality at the reactive site shows inversion of configuration
Answer: Option (1)
Explanation:
Enantiomers are defined as non-superimposable mirror images of each other.
Therefore, the statement that enantiomers are superimposable mirror images is incorrect.
A racemic mixture contains equal amounts of two enantiomers, and their optical rotations cancel each other, resulting in zero net optical rotation.
In an \mathrm{S}_{\mathrm{N}}1 reaction, a planar carbocation intermediate is formed,
which can be attacked from either side with equal probability.
As a result, the \mathrm{S}_{\mathrm{N}}1 reaction generally produces a 1:1 mixture of both enantiomers.
In an \mathrm{S}_{\mathrm{N}}2 reaction, nucleophilic attack occurs from the backside,
leading to inversion of configuration at the chiral carbon atom.
Hence, option (1) is the incorrect statement regarding chirality.