Question

Why grignard reagent is prepared under anhydrous condition

Answer 1

Grignard reagents are very reactive. In the presence of moisture, they react to give alkanes. Therefore, Grignard reagents should be prepared under anhydrous conditions.
Because Grignard reagent react with water to give corresponding alkanes, therefore they are prepared under anhydrous conditions.

RMgX+H2O→R−H+Mg(OH)XRMgX+H2O→R−H+Mg(OH)X

Answer 2

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Grignard reagent should be prepared under anhydrous conditions, because it is very reactive. It reacts very quickly with any source of proton to give hydrocarbon. It reacts with water very quickly. Therefore, it is necessary to avoid moisture from the Grignard reagents.