Assertion : trans-butene on reaction with bromine forms racemic mixture. Reason : trans-compound in trans addition forms two types of stereoisomers.

• A

  If both assertion and reason are true and reason is the correct explanation of assertion.
• B

  If both assertion and reason are true but reason is not the correct explanation of assertion.
• C

  If assertion is true but reason is false.
• Correct answer
  D

  If both assertion and reason are false.

Solution

With trans-but-2-ene, the product of \(\mathrm{Br}_2\) addition is optically inactive due to the formation of symmetric meso compounds.

In general, for symmetrical alkenes and symmetrical reagents, the addition takes place as: \(\begin{gathered} \text { cis-alkene }+ \text { syn-addition } \rightarrow \text { meso } \\ \text { trans-alkene }+ \text { syn-addition } \rightarrow \text { racemic } \\ \text { cis-alkene }+ \text { anti-addition } \rightarrow \text { racemic } \\ \text { trans-alkene }+ \text { anti-addition } \rightarrow \text { meso } \end{gathered}\)

Hence, the correct answer is option: 'D'.