Question

Assertion: $2 - butyne$ on treatment with $NaN{H_2}$ followed by acidification yields $1 - butyne$.
Reason: Alkynes isomerizes on treatment with a strong base.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C. Assertion is correct but Reason is incorrect.
D. Both Assertion and Reason are incorrect.

Answer 1

Hint: As we know that, $2 - butyne$ and $1 - butene $ are unsaturated compounds, both of them contain triple bonds and four carbon atoms. But the position of the triple bond is different, in $1 - butyne$ the triple bond is present on first carbon, whereas in $2 - butyne$ the triple bond is present on second carbon.

Complete step by step solution
When $2 - butyne$ react with sodamide through acidification, it gives $1 - butyne$. In sodium amide $NaN{H_2}$, sodium has $ + 1$ oxidation state and it no longer stays as reducing agent however, the amide ion $N{H_2}^ - $ is very strong base as we know that the $p{k_a}$ value of ammonia is $38$ so $NaN{H_2}$ is way of deprotonation of some organic compounds including terminal alkynes.
The proton attached to the terminal carbon in a terminal alkyne is acidic enough to react with sodium amide, forming the corresponding carbanion. Such carbanions are good nucleophiles and can be used in many synthetic procedures involving nucleophiles, such as addition to a carbonyl, as given here.
When $2 - butyne$ is reacted with sodamide followed by acidification yield $1 - butyne$. The reason for that is given as alkynes isomerizes on treatment with a strong base. We know that terminal alkyne when reacted with sodamide and passed out in isomerization equilibrium then $1 - butyne$ is formed as a product.
Therefore, the correct answer is both reason and assertion are correct but reason is not the correct explanation for the assertion.

So the correct option is (b).

Note:
Butyne are hydrocarbons and have a general formula ${C_n}{H_{2n - 2}}$. They contain a triple bond in their structure.