Question:medium

In the reaction, HCHO + CH\(_3\)MgI \(\rightarrow\) A \(\rightarrow\) H\(_2\)O \(\rightarrow\) B + Mg(OH)I. What are A and B?

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Grignard reagents add to aldehydes to give primary alcohols.
Updated On: Jun 16, 2026
  • CH\(_3\)OMgI and CH\(_3\)OH
  • CH\(_3\)CH\(_2\)OMgI and C\(_2\)H\(_5\)OC\(_2\)H\(_5\)
  • CH\(_3\)CH\(_2\)OMgI and CH\(_3\)CH\(_2\)OH
  • CH\(_3\)CH\(_2\)I and CH\(_3\)CH\(_2\)OH
Show Solution

The Correct Option is C

Solution and Explanation

To solve this problem, we need to understand the reaction sequence when formaldehyde (HCHO) reacts with methyl magnesium iodide (CH\(_3\)MgI). Let's break down the steps:

Step 1: Reaction of Formaldehyde with Grignard Reagent (CH\(_3\)MgI)

Grignard reagents, such as CH\(_3\)MgI, act as nucleophiles. In this reaction, the CH\(_3^-\) ion from the Grignard reagent attacks the electrophilic carbon of the carbonyl group in HCHO.

The nucleophilic addition results in the formation of an intermediate compound where the original carbonyl oxygen now carries a negative charge. Magnesium iodide (MgI\(^+\)) binds with this negatively charged oxygen.

\(\text{HCHO} + \text{CH}_3\text{MgI} \longrightarrow \text{CH}_3\text{CH}_2\text{OMgI} \quad (A)\)

Step 2: Hydrolysis of the Intermediate Compound

On addition of water (H\(_2\)O), the intermediate compound (CH\(_3\)CH\(_2\)OMgI) undergoes hydrolysis. The nucleophile, OH\(^-\) from water, will replace the MgI part, forming an alcohol and magnesium hydroxide iodide (Mg(OH)I).

\(\text{CH}_3\text{CH}_2\text{OMgI} + \text{H}_2\text{O} \longrightarrow \text{CH}_3\text{CH}_2\text{OH} \quad (B) + \text{Mg(OH)I}\)

Hence, the compounds formed in this reaction are:

  • A is CH\(_3\)CH\(_2\)OMgI
  • B is CH\(_3\)CH\(_2\)OH

Therefore, the correct answer is CH\(_3\)CH\(_2\)OMgI and CH\(_3\)CH\(_2\)OH.

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