Question

Assertion : trans-Butene on reaction with bromine forms racemic mixture.

Reason : trans-Compound in trans addition forms two types of stereoisomers .

(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not correct explanation of A

(c) A is true but R is false

(d) A and R are false

Answer 1

Correct option (d) A and R are false

Explanation:

With trans-but-2-ene, the product of Br₂ additionis optically inactive due to the formation of symmetric meso compounds.

In general, for symmetrical alkenes and symmetrical reagents, the addition takes place as :

cis-alkene + syn-addition →  meso

trans-akene + syn-addition →  racemic

cis-alkene + anti-addition  → racemic

trans-alkene + anti-addition → meso