Question

Which one of the following is the correct order of reagents to be used to convert [A] to [X]?

• A. KCN / H$_2$O$^-$, PCC, PCl$_5$, LiAlH$_4$
• B. PCC, PCl$_5$, LiAlH$_4$, KCN / H$_2$O$^-$
• C. LiAlH$_4$, KCN / H$_2$O$^-$, PCC, PCl$_5$
• D. PCC, KCN / H$_2$O$^-$, LiAlH$_4$, PCl$_5$

Hint:

Always remember the order of reagents in organic transformations, especially when performing oxidation, reduction, and nucleophilic substitution. The sequence of reagents is crucial for achieving the desired conversion.

Answer 1

The Correct Option is B

To convert the compound [A] to [X], the sequence of reagents should be chosen such that each reagent carries out a specific reaction step.
Step 1:
The conversion of the alcohol group in [A] to an aldehyde requires PCC, which is a mild oxidizing agent that oxidizes alcohols to aldehydes.
Step 2:
Next, PCl$_5$ is used to convert the aldehyde group into an acyl chloride (R-CCl).
Step 3:
Then, LiAlH$_4$ is used for reducing the acyl chloride to a corresponding alcohol.
Step 4:
Finally, KCN / H$_2$O$^-$ is used to convert the alcohol to the final product [X], which involves nucleophilic substitution, likely yielding the required structure.