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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:
2,4,6-Trichloroaniline can be prepared by reaction of dry aniline with chlorine gas while in an anhydrous solution of carbon tetrachloride. 2,4,6-Trichloroaniline precipitates from solution as a white solid. In the presence of water in the solution the white material will be contaminated with aniline black. [3]
Aniline is predominantly used for the preparation of methylenedianiline and related compounds by condensation with formaldehyde. The diamines are condensed with phosgene to give methylene diphenyl diisocyanate, a precursor to urethane polymers. [7] Most aniline is consumed in the production of methylenedianiline, a precursor to polyurethanes.
Steam distillation is a separation process that consists of distilling water together with other volatile and non-volatile components. The steam from the boiling water carries the vapor of the volatiles to a condenser; both are cooled and return to the liquid or solid state, while the non-volatile residues remain behind in the boiling container.
Below is a laboratory synthesis of 4-nitroaniline from aniline. The key step in this reaction sequence is an electrophilic aromatic substitution to install the nitro group para to the amino group. The amino group can be easily protonated and become a meta director. Therefore, a protection of the acetyl group is required.
An alternative mechanism is based on the aniline and the aldehyde forming at first the Schiff base upon water elimination. The subsequent reaction with the enol form of pyruvic acid ( 1 ) leads to the formation of the above-mentioned aniline derivative ( 3 ) followed by the above-described reaction mechanism: [ 4 ]
Direct nitration of aniline is inefficient since anilinium is produced instead. Nitration of acetanilide gives only traces of 2-nitro isomer is obtained due to the great steric effect of the amide. Sulfonation is usually used to block the 4 position and increases the effectiveness to 56%. [3] [4] Laboratory routes to produce 2-nitroaniline
N,N-Dimethylaniline (DMA) is an organic chemical compound, a substituted derivative of aniline. It is a tertiary amine, featuring a dimethylamino group attached to a phenyl group. This oily liquid is colourless when pure, but commercial samples are often yellow. It is an important precursor to dyes such as crystal violet.