The Sandmeyer Reaction 4-Chlorotoluene and 2-lodobenzoic Acid

Prelab Exercise Outline the steps necessary to prepare 4-bromotoluene, 4-iodotoluene, and 4-fluorotoluene from benzene. 

The Sandmeyer reaction is a versatile means of replacing the amine group of a primary aromatic amine with a number of different substituents  

The diazonium salt is formed by the reaction of nitrous acid with the amine in acid solution. Nitrous acid is not stable and must be prepared in situ in strong acid it dissociates to form nitroso ions, NO, which attack the nitrogen of the amine. The intermediate so formed loses a proton, rearranges, and finally loses water to form the resonance-stabilized diazonium ion. 

The diazonium ion is reasonably stable in aqueous solution at 0 C on warming up it will form phenol, as seen on the previous page. A versatile functional group, it will undergo all of the reactions depicted above as well as couple to aromatic rings activated with substituents such as amino and hydroxyl groups to form the huge class of azo dyes (see Chapter 66). 

Diazonium salts are not ordinarily isolated, because the dry solid is explosive. 

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Chapter 42 The Sandmeyer Reaction 4-Chlorotoluene and 2-lodobenzoic Acid... 

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