Chapter 9.6, Problem 9.32P

What reagents would you use to achieve each of the following transformations:

Interpretation Introduction

Interpretation:

Reagents that can be used to achieve the given transformation has to be identified.

Concept Introduction:

Amines react with nitrous acid to form diazonium salt.  Nitrous acid is prepared in the reaction flask itself by the use of sodium nitrite and hydrochloric acid.  Nitrous acid is protonated to produce highly reactive intermediate known as nitrosonium ion.  Nitrosonium ion when reacted with amine results in the formation of nitrosoamine.

If a primary amine is considered, then tautomerization takes place resulting in formation of diazonium ion.  This can be represented as,

Sandmeyer reaction:

Aryldiazonium salt reacts with copper salts as reagent to obtain the required aryl halides, aryl cyanides etc.  General scheme can be given as shown below,

Explanation of Solution

Given transformation is,

Product is an aryl halide while the starting material is an aryl amine.  The route that can be used to accomplish the above reaction is the Sandmeyer reaction.  In this the first step is the formation of aryl diazonium salt by the treatment of primary amine with sodium nitrite and hydrochloric acid.  Second step is the treatment of aryldiazonium salt with copper bromide to form the aryl bromide.

The scheme can be given as shown below,

The reagents that are used are sodium nitrite with hydrochloric acid and copper(I) bromide.