Question

Assertion: Ethyne reacts with sodium metal and sodamide to form sodium acetylide with the liberation of dihydrogen gas.
Reason: Alkynes are highly unsaturated.
(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: The statement given as assertion refers to an organic reaction with alkynes. Determine if the product mentioned matches with the reaction mechanism. Now determine if the Reason mentioned below is the correct explanation of the reaction mechanism. Based on this you can determine the correct answer.

Complete answer:
> The hydrogen atoms present in ethyne molecules are attached to sp hybridized carbon atoms which are relatively more electronegative. Thus, the hydrogen atoms are released easily in the form of protons and ethyne behaves as an acid.
> This is the reason it reacts with sodamide leading to the formation of sodium acetylide.
> Thus, the assertion statement is correct.

We will now try to understand the reason statement.
> Alkynes have a triple bond between two carbon atoms. Thus, the degree of unsaturation is 2.
> We can say that alkynes are highly unsaturated when comparison is being made with alkanes and alkenes.
> So, the reason statement is true as well.

Therefore, the correct answer is option (B).

Note: It is important to understand that although assertion and reason statements were true, the correct answer is option (B) only. This is because the unsaturation of alkynes does not explain the reaction of alkynes with bases like sodamide. Thus, reason is not the correct explanation of assertion.