Question

An unknown compound $\left(A\right)$ has a molecular formula $C_4{H}_6$. When $\left(A\right)$ is treated with excess of $B{r}_2$ a new substance $\left(B\right)$ with formula $C_4{H}_{6}B{r}_4$ is formed. $\left(A\right)$ forms a white ppt. with ammonical silver nitrate solution. $\left(A\right)$ may be :

• A. But$-1-$yne
• B. But$-2-$yne
• C. But$-1-$ene
• D. But$-2-$ene

Answer 1

Answer: (A)

But$-1-$yne

• The formula is $C_4{H}_6$. It corresponds to alkyne (i.e. $C_4{H}_{2\left(4\right)-2}$). i.e. Butyne.
• It is confirmed by the fact that it gives addition reaction with excess $B{r}_2$ and gets converted into $\left(C_4{H}_{6}B{r}_4\right)$
• Now Butyne can be 1-butyne or 2-butyne
• But only terminal alkyne reacts with Tollens reagent as they have acidic proton. (i.e. with ammonical $AgN{O}_3$) solution.
• Hence the compound is But-1-yne.