Question

The most suitable reagent for the conversion of $RCH_2OH \to RCHO$ is

• A. $KMnO_4$
• B. $K_2Cr_2O_7$
• C. $CrO_3$
• D. $PCC$ (pyridine chloro chromate)

Answer 1

Answer: (D)

$PCC$ (pyridine chloro chromate)

Answer 2

Pyridinium chlorochromate (PCC) $\left( C _{5} H _{5} NHCrO _{3} Cl ^{-}\right)$is a very good oxidising agent for converting $1^{\circ}$ alcohol to aldehydes and $2^{\circ}$ alcohols to ketone. It prevents further oxidation of aldehydes to carboxylic acid.
$\underset{\text{p-alcohol}}{RCH_2OH} \xrightarrow[CH_2Cl_2 \text{solvent}]{(CH_2H_5N)_2CrO_3} \underset{\text{Aldehyde}}{RCHO} + H_2O$
[PCC is prepared by mixing pyridine $\left( C _{5} H _{5} N \right), CrO _{3}$ and $HCl$.
$ROH \xrightarrow[\text { acidified } K _{2} Cr _{2} O _{7}]{\text{alkaline} KMnO_4 or}$ Carboxylic acid
$ROH \xrightarrow{ CrO _{3} / CH _{3} COOH }$ aldehyde