Question

R-CH\(_2\)OH is converted into R-CHO by reacting with ______
 

• A. Alkaline KMnO\(_4\)
• B. LiAlH\(_4\)
• C. Na/C\(_2\)H\(_5\)OH
• D. PCC (Pyridinium Chlorochromate)

Hint:

Remember the classification of oxidizing agents. Strong agents like KMnO\(_4\) and K\(_2\)Cr\(_2\)O\(_7\) oxidize primary alcohols to carboxylic acids. Mild agents like PCC and PDC (Pyridinium Dichromate) stop the oxidation at the aldehyde stage.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks for a reagent that can convert a primary alcohol (R-CH\(_2\)OH) into an aldehyde (R-CHO).
This is a specific oxidation reaction where the oxidation must be stopped at the aldehyde stage and not proceed further to a carboxylic acid.
Step 2: Analyzing the Options:
(A) Alkaline KMnO\(_4\): Potassium permanganate is a strong oxidizing agent. It oxidizes primary alcohols completely to carboxylic acids (R-COOH).
(B) LiAlH\(_4\): Lithium aluminium hydride is a strong reducing agent. It is used to reduce aldehydes, ketones, and carboxylic acids to alcohols. It will not oxidize an alcohol.
(C) Na/C\(_2\)H\(_5\)OH: This combination is used for the Bouveault-Blanc reduction, which reduces esters to alcohols. It is a reducing agent.
(D) PCC (Pyridinium Chlorochromate): PCC is a mild and selective oxidizing agent. It is specifically used to oxidize primary alcohols to aldehydes and secondary alcohols to ketones. It does not oxidize aldehydes further to carboxylic acids.
Step 3: Conclusion:
To convert a primary alcohol (R-CH\(_2\)OH) to an aldehyde (R-CHO), a mild oxidizing agent is required. Among the given options, PCC is the most suitable reagent for this conversion.
\[ \text{R-CH}_2\text{OH} \xrightarrow{\text{PCC}} \text{R-CHO} \] Step 4: Final Answer:
The correct reagent is PCC (Pyridinium Chlorochromate).