Question

How would you distinguish experimentally between an alcohol and a carboxylic acid?

Answer 1

Distinguishing between Carboxylic acid and Alcohol:-

• We can distinguish between Carboxylic acid and Alcohol by the Sodium bicarbonate$\left({\mathrm{Na}}_2{\mathrm{CO}}_3\right)$ test.
• When a Carboxylic acid is reacted with Sodium bicarbonate, it produces a brisk effervescence of Carbon dioxide.
• The reaction is:

$\underset{\mathrm{Carboxylic}\mathrm{acid}}{\mathrm{R}-\mathrm{COOH}\left(\mathrm{aq}\right)}+\underset{\mathrm{Sodium}\mathrm{bicarbinate}}{{\mathrm{Na}}_2{\mathrm{CO}}_3\left(\mathrm{s}\right)}\to \underset{\mathrm{Sodium}\mathrm{acetate}}{\mathrm{R}-\mathrm{COONa}\left(\mathrm{aq}\right)}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2\left(\mathrm{g}\right)(\uparrow )}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

• This Carbon dioxide gas produced turns lime water milky.
• When an Alcohol reacts with Sodium bicarbonate, it does show any such reactions

$\underset{\mathrm{Alcohol}}{\mathrm{R}-\mathrm{OH}\left(\mathrm{aq}\right)}+\underset{\mathrm{Sodium}\mathrm{bicarbonate}}{{\mathrm{Na}}_2{\mathrm{CO}}_3\left(\mathrm{s}\right)}\to \mathrm{No}\mathrm{reaction}$

Therefore, Carboxylic acid and Alcohol can be distinguished by using Sodium bicarbonate as, Carboxylic acid produces a brisk effervesce when reacted with it, whereas Alcohols do not produce anything when reacted with Sodium bicarbonate.