NEET 2022 Chemistry Grignard Reagents MCQ Question

Chapter: Hydrocarbons

Class: 11 Topic: Grignard Reagent with $CO_2$ Difficulty: 🟡 Moderate

✅ Ans: C — $RCOOMgX$

A Grignard reagent is:

$$RMgX$$

It reacts with carbon dioxide:

$$RMgX + CO_2 \rightarrow RCOOMgX$$

Here, the $R$ group gets attached to the carbon of $CO_2$, forming a magnesium carboxylate.

Then, on treatment with $H_3O^+$:

$$RCOOMgX + H_3O^+ \rightarrow RCOOH$$

So the intermediate $Y$ is:

$$\boxed{RCOOMgX}$$

❌ Why others are wrong?

• A: $RCOOX^-$ → incorrect product.
• B: $(RCOO)_2Mg$ → not the intermediate formed from one $RMgX$.
• D: $R_3COMgX$ → does not form with $CO_2$.

📌 NCERT: Grignard reagent + $CO_2$, followed by hydrolysis, gives a carboxylic acid.

🧠 NEET Trick:

$$\boxed{RMgX \xrightarrow{CO_2} RCOOMgX \xrightarrow{H_3O^+} RCOOH}$$

Therefore, $Y = RCOOMgX$ → Option C.