Question

Deduce the structural of a compound A $\left(C_6{H}_{10}\right)$ which shows the following reactions.
i. Adds 2 mol of $H_2$ to form 2-methyl pentane.
ii. Reacts with aqueous $H_{2}S{O}_4+HgS{O}_4$ solution to give a carbonyl compound.
iii. Does not react with ammoniacal $AgN{O}_3$ solution.

• A. 4- methyl pent-2- yne
• B. 4- methyl pent- 1- yne
• C. 2 methyl 1,3 butadiene
• D. 1,2 dimethyl cyclobut- 3- ene

Answer 1

Answer: (A)

4- methyl pent-2- yne

i. Adds 2 mol of $H_2$ to form 2-methyl pentane. Hence, it contains a $C\equiv C$ triple bond or two $C=C$ double bonds or a ring and a double bond or two rings.

ii. Reacts with aqueous $H_{2}S{O}_4+HgS{O}_4$ solution to give a carbonyl compound. Hence, it contains a $C\equiv C$ triple bond to which a molecule of water is added to form enol which tautomerizes to a ketone.

iii. Does not react with ammoniacal $AgN{O}_3$ solution. Hence, it is not a terminal alkyne.

Hence, the compound (A) is 4- methyl pent-2- yne.