The most suitable reagent for the conversion of $\mathrm{R}-\mathrm{CH}_{2}-\mathrm{OH} \longrightarrow \mathrm{R}-\mathrm{CHO}$ is:

(B) PCC (Pyridinium Chlorochromate)

(D) $\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}$

JEE Main · 2014 · 06 Apr 2014 · Offline · Alcohols Phenols and Ethers

The most suitable reagent for the conversion of

R - CH_{2} - OH ⟶ R - CHO

is:

(A) $CrO_{3}$
(B)PCC (Pyridinium Chlorochromate)✓ Correct
(C) $KMnO_{4}$
(D) $K_{2} Cr_{2} O_{7}$

Answer: (B)

Solution

Turning a primary alcohol into an aldehyde needs an oxidant gentle enough to stop at the aldehyde and not push on to the acid. Pyridinium chlorochromate does exactly that, taking

RCH X_{2} OH

RCHO

under anhydrous conditions. The stronger oxidants

CrO X_{3}

KMnO X_{4}

and

K X_{2} Cr X_{2} O X_{7}

would carry it all the way to the carboxylic acid, so PCC is the reagent to choose.

JEE Main · 2014 · 06 Apr 2014 · Offline · Single correct option

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