RMgX + CO₂ \(\rm \xrightarrow[ether]{dry}\) Y \(\rm \xrightarrow{ \ \ H_3O^+ \ \ }\) RCOOH 

What is Y in the above reaction?

Concept:

Reaction of Grignard reagent with CO₂ - 

• It is an important method of preparation of carboxylic acid.
• Grignard reagent behaves as a nucleophile which attacks the substrate CO₂  in presence of dry ether and forms a nucleophilic addition product.
• This nucleophilic addition product is a salt of carboxylic acid which on acidification yields carboxylic acid.

Explanation:

In the given reaction, R-MgX is the Grignard reagent and CO₂ (dry ice) is the substrate.

The reaction is complete in two steps-

1. Attack of Grignard reagent on CO₂ - the nucleophile Grignard reagent attack the CO₂ in presence of dry ether and as a carboxylic acid salt is formed as product name as 'Y'  in the above reaction.
2. Acidification of the carboxylic salt - It gives carboxylic acid as a final product.

It can be represented as -

R^δ--^δ+MgX + O=C=O \(\xrightarrow{dry \hspace{0.1cm}ether}\) RCOO- Mg+X \(\xrightarrow{H_3O^+}\) RCOOH

So, RCOO- Mg+X is obtained as an intermediate product (Y) in the given reaction.

Hence, the correct answer is option 2.