Diazotisation and coupling reaction

Diazotisation and coupling reaction

1. PRESENTED BY – BUDDHADEV DEY B.PHARM ,2 nd year, 3 rd semester DIAZOTISATION AND COUPLING REACTION

2. -: Diazotization Reaction:- Diazo means two nitrogen atoms. When combined with onium , we have diazonium , which means two nitrogen atoms and a positive charge (i.e., N 2 + ). Diazonium ions are produced when an aryl amine reacts with cold nitrous acid. Nitrous acid is unstable and is prepared just prior to its use by a reaction between sodium nitrite and hydrochloric acid. Reaction:-

3. Mechanism of reaction:-

4. -: coupling reaction:- Compounds such as aniline and phenol, which contain strong electron donating groups (e.g., -OH and –NH 2 ) that activate the ortho and para positions on a benzene ring, can undergo coupling reactions with a diazonium ion. A coupling reaction is one in which two aryl rings are joined by an azo group. These coupling reactions usually occur at the para position of the o,p director. Aniline may serve as the substrate for the formation of a diazonium ion, and it may serve as the substrate for a coupling reaction with the diazonium ion. The reaction is an electrophilic aromatic substitution reaction; therefore, the mechanism is similar to that for the nitration of benzene (i.e., it is a two-step reaction in which the first step is rate determining).

5. Coupling reaction with phenol

6. Mechanism of coupling with phenol:-

7. Mechanism of coupling with aniline:-

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