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2,4,6-Tribromoaniline can be prepared by treating bromine water with aniline in a solution of acetic acid or dilute hydrochloric acid: [1] By reacting bromine with aniline in water, a white precipitate immediately forms and that is 2,4,6-tribromoaniline
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:
The reaction of anthracene with N-methylformanilide, also using phosphorus oxychloride, gives 9-anthracenecarboxaldehyde: N -Methylformanilide and anthracene and phosphorus oxychloride In general, the electron-rich arene ( 3 ) must be much more active than benzene for the reaction to proceed; phenols or anilines are good substrates.
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:
The reaction mechanism for this reaction has been demonstrated to proceed through steps similar to those known for palladium catalyzed CC coupling reactions. Steps include oxidative addition of the aryl halide to a Pd(0) species, addition of the amine to the oxidative addition complex, deprotonation followed by reductive elimination .
This is also called the Wohl–Ziegler reaction. [7] [8] The carbon tetrachloride must be maintained anhydrous throughout the reaction, as the presence of water may likely hydrolyze the desired product. [9] Barium carbonate is often added to maintain anhydrous and acid-free conditions.
The Hofmann rearrangement (Hofmann degradation) is the organic reaction of a primary amide to a primary amine with one less carbon atom. [1] [2] [3] The reaction involves oxidation of the nitrogen followed by rearrangement of the carbonyl and nitrogen to give an isocyanate intermediate.
4-Bromoaniline is a compound where an aniline molecule is substituted with a bromine atom on the para position. Commercially available, this compound may be used as a building block, e.g. in the preparation of monobrominated biphenyl via the Gomberg-Bachmann reaction .