COMEDK · Chemistry · 14. Hydrocarbons
The conversion of Propyne to Benzene can be brought out in 4 steps.
Choose the reagents to be used, in the proper sequential order, to bring out the conversion.
Reagents provided: alc. \(\mathrm{KOH}, \mathrm{H}_2 / \mathrm{Pd}, \mathrm{Na} /\) dry ether, \(\mathrm{HBr}, \mathrm{HBr} /\left(\mathrm{C}_6 \mathrm{H}_5 \mathrm{CO}\right)_2 \mathrm{O}_2\),
Soda-lime, \(\mathrm{Cr}_2 \mathrm{O}_3\) (high T and P), Conc. \(\mathrm{H}_2 \mathrm{SO}_4\)
- A \(\mathrm{Cr}_2 \mathrm{O}_3\) (high \(\mathrm{T}\) and \(\mathrm{P}\)), \(\mathrm{Na} /\) dry ether, \(\mathrm{HBr}\), Conc. \(\mathrm{H}_2 \mathrm{SO}_4\)
- B \(\mathrm{H}_2 / \mathrm{Pd}, \mathrm{HBr} /\left(\mathrm{C}_6 \mathrm{H}_5 \mathrm{CO}\right)_2 \mathrm{O}_2, \mathrm{Na} /\) dry ether, \(\mathrm{Cr}_2 \mathrm{O}_3\) (high \(\mathrm{T}\) and \(\mathrm{P}\))
- C \(\mathrm{Na} /\) Ether, \(\mathrm{Cr}_2 \mathrm{O}_3\) (high \(\mathrm{T}\) and \(\mathrm{P}\)), \(\mathrm{HBr}, \mathrm{H}_2 / \mathrm{Pd}\)
- D \(\mathrm{HBr}\), alc. \(\mathrm{KOH}, \mathrm{HBr} /\left(\mathrm{C}_6 \mathrm{H}_5 \mathrm{CO}\right)_2 \mathrm{O}_2, \mathrm{Cr}_2 \mathrm{O}_3\) (high \(\mathrm{T}\) and \(\mathrm{P}\))
Answer & Solution
Correct Answer
(B) \(\mathrm{H}_2 / \mathrm{Pd}, \mathrm{HBr} /\left(\mathrm{C}_6 \mathrm{H}_5 \mathrm{CO}\right)_2 \mathrm{O}_2, \mathrm{Na} /\) dry ether, \(\mathrm{Cr}_2 \mathrm{O}_3\) (high \(\mathrm{T}\) and \(\mathrm{P}\))
Step-by-step Solution
Detailed explanation
The conversion of propyne (\(CH_3-C \equiv CH\)) to benzene (\(C_6H_6\)) involves the following steps: Step 1: Partial hydrogenation of propyne to propene using \(H_2 / Pd\) (Lindlar catalyst or poisoned Pd). \(CH_3-C \equiv CH + H_2 \xrightarrow{Pd} CH_3-CH=CH_2\) Step 2:…
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