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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]
The hydrochloric acid and sodium hydroxide byproducts undergo a secondary reaction to release the byproducts of water and sodium chloride. The overall reaction is thus NaOCl + 2NH 3 → N 2 H 4 + NaCl + H 2 O. Excess ammonia and sodium chloride are removed by distillation, followed by azeotropic distillation with aniline to remove water.
The name "Schotten–Baumann reaction conditions" often indicate the use of a two-phase solvent system, consisting of water and an organic solvent. The base within the water phase neutralizes the acid, generated in the reaction, while the starting materials and product remain in the organic phase, often dichloromethane or diethyl ether.
The reaction mechanism is not exactly known; two proposals are presented here. One possibility is at first an aldol condensation, starting from the enol form of the pyruvic acid (1) and the aldehyde, forming an β,γ-unsaturated α-ketocarboxylic acid (2). This is followed by a Michael addition with aniline to form an aniline derivative (3).
Dimethylaniline undergoes many of the reactions expected for an aniline, being weakly basic and reactive toward electrophiles. [6] It is nitrated to produce tetryl, a derivative with four nitro groups which was once used as explosive. In acidic solution, the initial nitration gives 3-nitrodimethylaniline. [7]
It has a fishy odor and is miscible with water. Like other amines, it is a weak base , compared to strong bases such as NaOH , but it is a stronger base than its aromatic analog, aniline . It is a useful intermediate in the production of many other organic compounds (e.g. cyclamate )