In the reaction RMgX + CO2 ->[dry ether] Y ->[H3O+] RCOOH, the intermediate Y is:

Correct answer: (A) (A) R-COO^- Mg^+ X. The Grignard reagent adds across one C=O of CO2: the nucleophilic R group attacks carbon, giving the magnesium carboxylate salt R-COO^- Mg^+ X (an 'acid magnesium halide'). Acidic aqueous work-up (H3O+) then protonates the carboxylate to the carboxylic acid RCOOH. This is the standard Grignard carboxylation route used to add one carbon as -COOH.

NEET 2022 · ChemistryPrevious Year Question

In the reaction $RMgX + CO X_{2} dry ether Y H X_{3} O X^{+} RCOOH$ , the intermediate Y is:

Answer: (A) (A) $R - COO X^{-} Mg X^{+} X$ . The Grignard reagent adds across one $C = O$ of $CO X_{2}$ : the nucleophilic R group attacks carbon, giving the magnesium carboxylate salt $R - COO X^{-} Mg X^{+} X$ (an 'acid magnesium halide').

A.(A) $R - COO X^{-} Mg X^{+} X$ ✓
B.(B) $R X_{3} C - O X^{-} Mg X^{+} X$
C.(C) $R - COO X^{-} X X^{+}$
D.(D) $(RCOO) X_{2} Mg$

Correct Answer

(A) (A) $R - COO X^{-} Mg X^{+} X$

Solution & Explanation

The Grignard reagent adds across one $C = O$ of $CO X_{2}$ : the nucleophilic R group attacks carbon, giving the magnesium carboxylate salt $R - COO X^{-} Mg X^{+} X$ (an 'acid magnesium halide'). Acidic aqueous work-up $(H X_{3} O X^{+})$ then protonates the carboxylate to the carboxylic acid $RCOOH$ . This is the standard Grignard carboxylation route used to add one carbon as $- COOH$ .

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In the reaction RMgX+COX2​dry ether​YHX3​OX+​RCOOH, the intermediate Y is:

Solution & Explanation

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In the reaction $RMgX + CO X_{2} dry ether Y H X_{3} O X^{+} RCOOH$ , the intermediate Y is: