COMEDK · Chemistry · 26. Alcohols Phenols and Ethers
Which one of the following is the correct order of reagents to be used to convent [A] to [X] ?
\(
\text { Reagents: } \mathrm{PCC}, \mathrm{PCl}_5, \mathrm{LiAlH}_4, \dfrac{\mathrm{KCN}}{\mathrm{H}_3 \mathrm{O}^{+}}\)
- A \(\mathrm{PCC} \quad \mathrm{PCl}_5 \quad \dfrac{K C N}{\mathrm{H}_3 \mathrm{O}^{+}} \quad \mathrm{LiAlH}_4\)
- B \(\dfrac{K C N}{H_3 \mathrm{O}^{+}} \quad \mathrm{PCl}_5 \quad \mathrm{PCC} \quad \mathrm{LiAlH}_4\)
- C \(\mathrm{LiAlH}_4, \dfrac{K C N}{H_3 \mathrm{O}^{+}} \quad \mathrm{PCl}_5 \quad \mathrm{PCC}\)
- D \(\mathrm{PCl}_5, \quad \dfrac{K C N}{H_3 \mathrm{O}^{+}} \quad \mathrm{LiAlH}_4 \quad \mathrm{PCC}\)
Answer & Solution
Correct Answer
(D) \(\mathrm{PCl}_5, \quad \dfrac{K C N}{H_3 \mathrm{O}^{+}} \quad \mathrm{LiAlH}_4 \quad \mathrm{PCC}\)
Step-by-step Solution
Detailed explanation
The goal is to convert \(R-CH_2-OH\) to \(R-CH_2-CHO\) (adding one carbon via chain extension). \(PCl_5\): Converts alcohol to alkyl chloride (good leaving group). \(R-CH_2-OH \xrightarrow{PCl_5} R-CH_2-Cl\) \(KCN\): Nucleophilic substitution adds cyanide, extending the chain by…
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