Ncert Exercises & Solutions

${CH}_{3} {CH}_{2} OH$ can be converted into ${CH}_{3} CHO$ by:
1. Catalytic hydrogenation
2. Treatment with LiAI $H_{4}$
3. Treatment with pyridinium chlorochromate
4. Treatment with KMn $O_{4}$

Hint: It is an oxidation reaction but the mild oxidizing agent is used

Ethanal ( ${CH}_{3} CHO$ ) is an oxidized product of ethanol. Pyridinium chlorochromate ( $C_{5} H_{5} {NH}^{+} {ClCrO}_{3}^{-}$ ) oxidizes primary alcohols to aldehydes. Strong oxidizing agents such as KMn $O_{4}$ are used for getting carboxylic acids from alcohols.

The oxidation process can be stopped at the aldehyde stage if Cr(VI) reagents such as Collin’s reagent ( ${CrO}_{3} . 2 C_{5} H_{5} N$ ), Corey's reagent, or pyridinium chlorochromate, and pyridinium dichromate [ ${(C_{5} H_{5} {NH}_{2})}^{2 +} C r_{2} O_{7}^{2 -}$ ] in the anhydrous medium are used as the oxidizing agent. So, the correct option is (3).

The reaction is as follows:

$CH_{3}CH_{2}OH\xrightarrow[]{PCC}CH_{3}COOH$

Alcohol does not undergo reaction with catalytic hydrogenation and also does not react with $LiAlH_{4}$ because both are reducing agents.

Ethanol when reacted with Potassium permanganate then ethanoic acid is obtained.

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