Question

A hydrocarbon which decolourises $KMn{O}_4$ but does not give any precipitate with ammoniated $AgN{O}_3$ is:

• A. benzene
• B. acetylene
• C. butyne
• D. 2-Butene

Answer 1

The correct option is D 2-Butene

2-Butene decolourises $KMn{O}_4$ but does not give any precipitate with ammoniated $AgN{O}_3$.
2-Butene reacts with hot alkaline $KMn{O}_4$ to form 2 moles of acetic acid.
$C{H}_3-C=C-C{H}_3\stackrel{\text{hot alkaline}KMn{O}_4}{\to }2C{H}_{3}COOH$
Since 2-Butene is an internal alkene, it does not react with $AgN{O}_3$.
Only terminal alkynes react with $AgN{O}_3$.