In the preparation of methyl benzoate, what is the purpose of (a) washing the organic layer with sodium bicarbonate solution

The purpose of washing the organic layer with sodium bicarbonate solution is to

(to remove any of the unreacted benzoic acid).

Explanation:

Methyl benzoate is a typical example of an ester in organic chemistry. It is formed by the action of benzoic acid and methanol. Sulphuric acid is often used as a catalyst in this reaction.

The procedure for the preparation of the ester includes:

--> the acid and the alcohol are added into a round bottom flask,

--> concentrated sulphuric acid is added down the side of the flask,

--> a separatory funnel is used to extract the ester into an organic layer where sodium bicarbonate is added.

--> when the aqueous layer from the sodium bicarbonate wash is acidified with concentrated HCl, the unreacted benzoic acid should precipitate. This is how the unreacted benzoic acid is removed.

See explanation

Explanation:

Let us remember that Sodium bicarbonate is basic in nature. It is one of the common bases used to neutralize acids.

In the preparation of methyl benzoate, H2SO4 is used as the catalyst for the esterification reaction.

Hence, when we wash the organic layer with sodium bicarbonate we are trying to remove the H2SO4 thereby neutralizing the organic layer.