Question

In an $S_{N}1$ reaction of alkyl halide on chiral centres there is :

• A. $100\%$ recemization
• B. inversion more than retention leading to partial racemization
• C. $100\%$ retention
• D. $100\%$ inversion

Answer 1

The correct option is B inversion more than retention leading to partial racemization

inversion more than retention to partial racemization.

The isomer corresponding to inversion is present in slight excess because SN1 also depends upon the degree of shielding of the front side of the reacting carbon.

In case of optically active alkyl halides. SN1 reaction is accompanied by racemisation. The carbocation formed in the slow step being sp2 hybridised is planar and attack of nucleophile may take place from either side resulting in a mixture of products, one having the same configuration and other having inverted configuration.