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For example, reaction of aniline with sulfuric acid at 180 °C produces sulfanilic acid, H 2 NC 6 H 4 SO 3 H. If bromine water is added to aniline, the bromine water is decolourised and a white precipitate of 2,4,6-tribromoaniline is formed. To generate the mono-substituted product, a protection with acetyl chloride is required:
Illustrative is the acetylation of aniline. First aniline is dissolved in water using one equivalent of hydrochloric acid. This solution is subsequently treated, sequentially, with acetic anhydride and aqueous sodium acetate. Aniline attacks acetic anhydride followed by deprotonation of the ammonium ion: Acetate then acts as a leaving group:
A white solid, it is the chloride salt of anilinium, which is the conjugate acid of aniline, C 6 H 5 NH 2. Anilinium chloride is produced by treatment of aniline with hydrochloric acid. The cation consists of a phenyl ring attached to a tetrahedral ammonium center. The C-N bond elongates from 1.41 Å in aniline to 1.474 Å in anilinium. [2]
Sulfanilic acid can be produced by sulfonation of aniline with concentrated sulfuric acid. [5] This proceeds via phenylsulfamic acid; a zwitterion with a N-S bond. Eugen Bamberger originally proposed a mechanism involving a series of intramolecular rearrangements, with phenylsulfamic acid forming orthanilic acid, which rearranged to sulfanilic acid on heating.
Schotten–Baumann reaction also refers to the conversion of acid chloride to esters. The reaction was first described in 1883 by German chemists Carl Schotten and Eugen Baumann. [1] [2] The name "Schotten–Baumann reaction conditions" often indicate the use of a two-phase solvent system, consisting of water and an organic solvent.
The reaction is faster at high pH. [2] Many other azo dyes have been prepared by similarly. Several procedures have been described in detail. [5] [6] [7] Naphthols are popular coupling agents. One example is the synthesis of the dye "organol brown" from aniline and 1-naphthol: Synthesis of organol brown from aniline and 1-naphthol
Aniline reacts with acyl chlorides or carboxylic anhydrides to give anilides. For example, reaction of aniline with acetyl chloride provides acetanilide ( CH 3 −CO−NH−C 6 H 5 ). At high temperatures, aniline and carboxylic acids react to give anilides.
General Gould-Jacobs reaction scheme. Specifically, 4-quinolinol can be synthesized. [3] In this reaction aniline or an aniline derivative first reacts with malonic acid derivative ethyl ethoxymethylenemalonate with substitution of the ethoxy group by nitrogen. A benzannulation takes place by application of heat to a quinoline.