Q39 / 150 · MHT CET 2026 (16 April Shift 2) · Chemistry
Which of the following reagents limits the oxidation of $\text{R-CH}_2\text{OH}$ up to R-CHO only?
- Correct answerAPCC
- B$\text{CrO}_3$
- C$\text{K}_2\text{Cr}_2\text{O}_7$ / dil. $\text{H}_2\text{SO}_4$
- D$\text{KMnO}_4$ (acidic)
Solution
Primary alcohols ($\text{R-CH}_2\text{OH}$) can be oxidized to aldehydes ($\text{R-CHO}$) or carboxylic acids ($\text{R-COOH}$) depending on the oxidizing agent used.
Strong oxidizing agents like acidic $\text{KMnO}_4$, $\text{K}_2\text{Cr}_2\text{O}_7$ / dil. $\text{H}_2\text{SO}_4$, and $\text{CrO}_3$ in aqueous medium oxidize primary alcohols directly to carboxylic acids.
To limit the oxidation to the aldehyde stage, mild oxidizing agents are required. Pyridinium chlorochromate (PCC) is a mild oxidizing agent that selectively oxidizes primary alcohols to aldehydes and prevents further oxidation to carboxylic acids.
$\text{R-CH}_2\text{OH} \xrightarrow{\text{PCC}} \text{R-CHO}$
Answer: PCC
Strong oxidizing agents like acidic $\text{KMnO}_4$, $\text{K}_2\text{Cr}_2\text{O}_7$ / dil. $\text{H}_2\text{SO}_4$, and $\text{CrO}_3$ in aqueous medium oxidize primary alcohols directly to carboxylic acids.
To limit the oxidation to the aldehyde stage, mild oxidizing agents are required. Pyridinium chlorochromate (PCC) is a mild oxidizing agent that selectively oxidizes primary alcohols to aldehydes and prevents further oxidation to carboxylic acids.
$\text{R-CH}_2\text{OH} \xrightarrow{\text{PCC}} \text{R-CHO}$
Answer: PCC
Hence, the correct answer is option: 'A'.