Comparison — PCC vs KMnO₄ vs LiAlH₄ vs NaBH₄ — Notes

Property	PCC	$KMnO_{4}$ / $K_{2}Cr_{2}O_{7}$	$LiAlH_{4}$	$NaBH_{4}$
Type	Mild oxidizing agent	Strong oxidizing agent	Strong reducing agent	Mild reducing agent
1° Alcohol → ?	Aldehyde (stops here)	Carboxylic acid	—	—
2° Alcohol → ?	Ketone	Ketone	—	—
3° Alcohol → ?	No reaction	No reaction (C-C cleavage)	—	—
Aldehyde → ?	No further action	Carboxylic acid	1° Alcohol	1° Alcohol
Ketone → ?	No reaction	No reaction	2° Alcohol	2° Alcohol
Carboxylic acid → ?	No reaction	No reaction	1° Alcohol	No reaction
Solvent	$CH_{2}Cl_{2}$ (anhydrous)	Aqueous	Anhydrous ether	Aqueous/EtOH

Critical NEET trap: $NaBH_{4}$ cannot reduce carboxylic acids. $LiAlH_{4}$ is required. PCC is the only reagent that stops oxidation at the aldehyde stage.