Question

Out of ‘X’ and ‘Y’, which one will undergo racemisation and why?

Hint:

Racemisation = $S_N1$ (two-step reaction). Walden Inversion = $S_N2$ (one-step reaction).

Answer 1

Out of ‘X’ and ‘Y’, which one will undergo racemisation and why?

Solution:
Racemisation occurs when a chiral compound undergoes a reaction that results in the formation of both enantiomers (optical isomers) in equal proportions, resulting in a racemic mixture.

Compound ‘X’ (1-Bromobutane) undergoes an SN1 mechanism due to the formation of a carbocation intermediate. In this case, the carbocation formed is planar and can be attacked from either side by the nucleophile (OH⁻). This leads to the formation of both the R and S enantiomers, resulting in racemisation.

Compound ‘Y’ (2-Bromobutane) undergoes an SN2 mechanism, where the nucleophile attacks the carbon bearing the leaving group from the opposite side. This mechanism results in the inversion of configuration and does not lead to racemisation, as only one stereoisomer is formed.

Conclusion:
Therefore, compound ‘X’ will undergo racemisation due to the SN1 mechanism, which involves the formation of a planar carbocation and allows attack from both sides, leading to the formation of a racemic mixture.