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NEET CHEMISTRYHaloalkanes and HaloarenesMedium

Question

C6H5CH2Br2. H3O+1. Mg, EtherX\text{C}_6\text{H}_5\text{CH}_2\text{Br} \xrightarrow[2.\text{ H}_3\text{O}^+]{1.\text{ Mg, Ether}} \text{X}

The product 'X' in the above reaction is:

A

C6H5CH2OH\text{C}_6\text{H}_5\text{CH}_2\text{OH}

B

C6H5CH3\text{C}_6\text{H}_5\text{CH}_3

C

C6H5CH2CH2C6H5\text{C}_6\text{H}_5\text{CH}_2\text{CH}_2\text{C}_6\text{H}_5

D

C6H5CH2OCH2C6H5\text{C}_6\text{H}_5\text{CH}_2\text{OCH}_2\text{C}_6\text{H}_5

Step-by-Step Solution

The reaction proceeds in two steps:

  1. Formation of Grignard Reagent: Benzyl bromide (C6H5CH2Br\text{C}_6\text{H}_5\text{CH}_2\text{Br}) reacts with magnesium (Mg\text{Mg}) in the presence of dry ether to form benzylmagnesium bromide (C6H5CH2MgBr\text{C}_6\text{H}_5\text{CH}_2\text{MgBr}), which is a Grignard reagent . C6H5CH2Br+Mgdry etherC6H5CH2MgBr\text{C}_6\text{H}_5\text{CH}_2\text{Br} + \text{Mg} \xrightarrow{\text{dry ether}} \text{C}_6\text{H}_5\text{CH}_2\text{MgBr}
  2. Hydrolysis: Grignard reagents are highly reactive and react with any source of a proton (like water, alcohols, or acids) to form corresponding hydrocarbons. Here, the addition of H3O+\text{H}_3\text{O}^+ (acidic hydrolysis) provides protons that react with the Grignard reagent to form toluene (C6H5CH3\text{C}_6\text{H}_5\text{CH}_3). C6H5CH2MgBr+H3O+C6H5CH3+Mg(OH)Br+H+\text{C}_6\text{H}_5\text{CH}_2\text{MgBr} + \text{H}_3\text{O}^+ \rightarrow \text{C}_6\text{H}_5\text{CH}_3 + \text{Mg}(\text{OH})\text{Br} + \text{H}^+

Thus, the final product 'X' is toluene (C6H5CH3\text{C}_6\text{H}_5\text{CH}_3).

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Haloalkanes and Haloarenes. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

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