The products A and B obtained in the following reactions, respectively, are 3 ROH + PCl 3 rightarrow 3 RCl + A ROH + PCl 5 rightarrow RCl + HCl + B

Chemistry · Alkyl and Aryl Halides

NEET (UG) 2024 — Question 83

The products $A$ and $B$ obtained in the following reactions, respectively, are

3 \mathrm{ROH}+\mathrm{PCl}_{3} \rightarrow 3 \mathrm{RCl}+\mathrm{A}

$\mathrm{ROH}+\mathrm{PCl}_{5} \rightarrow \mathrm{RCl}+\mathrm{HCl}+\mathrm{B}$

Option A:
$\mathrm{POCl}_{3}$ and $\mathrm{H}_{3} \mathrm{PO}_{3}$
Option B:
$\mathrm{POCl}_{3}$ and $\mathrm{H}_{3} \mathrm{PO}_{4}$
Option C:
$\mathrm{H}_{3} \mathrm{PO}_{4}$ and $\mathrm{POCl}_{3}$
Option D:
$\mathrm{H}_{3} \mathrm{PO}_{3}$ and $\mathrm{POCl}_{3}$
Correct

Answer: D

Step-by-step solution

With $\ce{PCl3}$ , three alkyl groups replace three $\ce{Cl}$ atoms: $\ce{3 ROH + PCl3 -> 3 RCl + H3PO3}$ . Thus $A = \ce{H3PO3}$ . With $\ce{PCl5}$ , one $\ce{Cl}$ forms the alkyl chloride and another forms $\ce{HCl}$ : $\ce{ROH + PCl5 -> RCl + HCl + POCl3}$ . Thus $B = \ce{POCl3}$ . Therefore the correct pair is $\ce{H3PO3}$ and $\ce{POCl3}$ , i.e. option D.

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Exam: NEET (UG) 2024
Paper: 2024 paper
Subject: Chemistry
Chapter: Alkyl and Aryl Halides
Topic: Introduction to Alkyl Halides and Methods of Preparation

The compound that will undergo S N 1 reaction with the fastest rate is

Answer: D

Step-by-step solution

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