Home › NEET UG › Chemistry › Haloalkanes and Haloarenes › Why is the carbocation formed in SN1 reactions r…
Why is the carbocation formed in SN1 reactions racemised when starting from an optically active substrate?
ABecause optical activity is lost on heating
BThe carbocation is sp²-hybridised, planar, and achiral. The nucleophile attacks both faces with equal probability → 50:50 mixture of enantiomers
CBecause the solvent changes optical rotation
DBecause the temperature drops
Answer & Solution
Correct answer: B. The carbocation is sp²-hybridised, planar, and achiral. The nucleophile attacks both faces with equal probability → 50:50 mixture of enantiomers
Key SN1 stereochemistry: the carbocation intermediate is **sp²-hybridised → planar → achiral**. Nucleophile attacks either face with equal probability → equal amounts of the two enantiomers → **racemisation**. (Some inversion-preference can occur via ion-pair effects, but textbook SN1 ⇒ racemic.)
Related questions
With which two hydrogen halides is the peroxide effect not observed?Addition anti to Markovnikov rule is known as the peroxide or:Who framed the rule for adding HBr to unsymmetrical alkenes, in 1869?An intermediate conformation between eclipsed and staggered is called:Eclipsed and staggered conformations are represented by Newman and:Across all conformations, what stays the same?How many conformations can an alkane have by rotation about single bonds?Spatial arrangements interconverted by rotation about a single bond are called: