Question

How can we distinguish between alcohol and carboxylic acid by alkaline $KMn{O}_4$ test?

Answer 1

Alkaline $KMn{O}_4$ acts as an oxidising agent, oxidising alcohols to carboxylic acids. While the reaction takes place, change in colour is observed. Initially we get a dark green colour due to the formation of $MnO{4}^{(2-)}$. The colour then changes to dark brown due to the formation of $Mn{O}_2$. Carboxylic acids do not give the same observation since they are not oxidised.