Question

\( CH_3C \equiv CCH_3 \xrightarrow{(i)\,X \; (ii)\,H_2O/Zn} CH_3CO - COCH_3 \)
In the above reaction \( X \) is:

• A. \(HNO_3\)
• B. \(O_2\)
• C. \(O_3\)
• D. \(KMnO_4\)

Hint:

Alkyne + \(O_3/Zn,H_2O\) → diketone. Alkyne + hot \(KMnO_4\) → carboxylic acids.

Answer 1

The Correct Option is C

Concept: Ozonolysis of alkynes gives diketones with reductive workup. \[ \text{Alkyne} \xrightarrow{O_3} \text{ozonide} \xrightarrow{Zn/H_2O} \text{dicarbonyl compound} \]

Step 1: Identify the reactant. \[ CH_3C \equiv CCH_3 \quad (\text{2-butyne, symmetrical alkyne}) \]

Step 2: Apply ozonolysis. Ozone cleaves the triple bond to form an ozonide.

Step 3: Reductive workup. \[ \text{ozonide} \xrightarrow{Zn/H_2O} CH_3COCOCH_3 \]

Step 4: Eliminate other options. \(KMnO_4\) gives acids (strong oxidation); \(O_2\) and \(HNO_3\) are not used for such cleavage.