Question

Given below are two statements for the following reaction sequence:

• A. Both Statement I and Statement II are true
• B. Statement I is false but Statement II is true
• C. Statement I is true but Statement II is false
• D. Both Statement I and Statement II are false

Hint:

Terminal alkynes give methyl ketones on hydration and undergo cyclotrimerisation to aromatic compounds at high temperatures.

Answer 1

The Correct Option is A

Step 1: Identify compound \(Y\)
\(X = \mathrm{C_3H_6Cl_2}\) is a vicinal/geminal dihalide.
Excess \(\mathrm{NaNH_2}\) causes double dehydrohalogenation. \[ \Rightarrow Y = \text{propyne } (\mathrm{CH_3C\equiv CH}) \]
Step 2: Formation of compound \(Z\)
Propyne undergoes acid-catalysed hydration in presence of \(\mathrm{Hg^{2+}}\).
Terminal alkyne hydration gives a methyl ketone. \[ Z = \text{acetone } (\mathrm{CH_3COCH_3}) \] Acetone gives a yellow precipitate of iodoform with NaOI. \[ \Rightarrow \text{Statement I is true.} \]
Step 3: Formation of compound \(Q\)
Propyne passed through a red hot iron tube undergoes cyclotrimerisation.
This produces mesitylene (\(1,3,5\)-trimethylbenzene), \(\mathrm{C_9H_{12}}\). In mesitylene:
Aromatic hydrogens = 3
Aliphatic hydrogens (three \(\mathrm{CH_3}\) groups) = 9 \[ \text{Aromatic : Aliphatic} = 3 : 9 = 1 : 3 \] \[ \Rightarrow \text{Statement II is true.} \] Final Conclusion: \[ \boxed{\text{Both Statement I and Statement II are true}} \]