Aniline 2,4,6-tribromo

It is also to he noted that ortho and para substitution often occur together in the same molecule, so that the group R enters the para and also both the ortho positions thus both aniline and phenol on bromination readily give symmetric (2,4,6) tribromo-compounds (p. 165), while both toluene and phenol on nitration readily give the symmetric trinitro-derivatives (p. 170). 

An alternative method of preparation consists in dissolving the aniline in 4 times its weight of glacial acetic acid in a beaker, and running in slowly from a tap funnel, while the solution is well stirred with a mechanical stirrer, the theoretical amount of bromine dissolved in twice its volume of glacial acetic acid. The beaker should be cooled in ice during the addition as the reaction is exothermic. The final product (a pasty mass) should be coloured yellow by the addition of a little more bromine if necessary. Pour into excess of water, filter at the pump, wash well with water, press thoroughly, and dry. The yield of tribromo-aniline, m.p. 119-120°, is quantitative. Recrystallise a small portion from methylated (or rectified) spirit m.p. 120°. 

Explain why the bromination of benzenamine (aniline) gives 2,4,6-tribromo-benzenamine (2,4,6-tribromoaniline), whereas the nitration with mixed acids gives 3-nitrobenzenamine (mefa-nitroaniline),... 

Tribromo- and -trichloro-aniline give nearly theoretical yields of 2,4,6-tribromo- Mid -trichloro- 1- nitrobenzene (100% Mid 98% respectively). 

Nitration followed by reduction forms aniline (C6H5NH2) from benzene (Steps [1] and [2]). Bromination of aniline yields the tribromo derivative in Step [3]. 

The electron affinities of the anilines can be compared to those of the phenols and halobenzenes. The Ea of the trichloranilines should be less than that for the trichlorphenols or about 0.6 eV. The NIMS for the anilines are very similar to that of the phenols, except that less loss of HX occurs. The Ea for the tribromo-anilines should be about 0.75 eV, while that for pentachloroaniline and pentabromo-aniline should be 1.1 eV and 1.4 eV. The CURES-EC values are 1.2 eV and 1.45 eV. 

On bromination of o- or /7-hydroxy- or o- or /7-amino-benzoic acid, or the corresponding sulfonic acids, even at room temperature, bromine replaces the COOH or S03H group with liberation of C02 or H2S04 as the case may be. At 40-45° the CHO group of o- or /7-hydroxy- or o- or /7-aminobenzaldehyde is also replaced by bromine, with evolution of CO. The end products are 2,4,6-tribromo-phenol or -aniline.460 Thus /7-hydroxybenzoic and sulfanilic acid, for example, can be determined quantitatively by means of O.lN-bromide-bromate solution. 

Tribromoacetanilide. Dissolve 1 g. of 2 4 6-tribromo-aniline In 20 ml. of acetic anhydride and add 2 drops of concentrated... 

Amines react very readily with the free halogens, the introduction of the halogen atom into the ring being greatly facilitated by the presence of the amino group. When an aqueous solution of aniline is treated with bromine-water, symmetrical tribromo-aniline is precipitated —... 

Pale yellow oil. B.p. 285-6°/710 mm. slight decomp., 185-5-186-5°/ 22 mm. D l-OOl, D 1-034. Insol, HjO. Sol. 5 parts EtOH. Weak base. Nascent Br —> 2 4 6-tribromo> ethylaniline. HNO —> 4-nitrosoethylbenzyl-aniline, m.p. 61-2°. HNO3+H[2S04 — ethyl-4-nitrobenzylaniline + ethyl-3-nitrobenzylanil-ine. EDfOj (D 1-5) + AcOH —> 4-nitroethyl-benzylaniline. Intermediate for triphenyb methane dyestuffs. 

Halogenation of aromatic sulphonic acids is often accompanied by displacement of the acid group by halogen. Thus chlorination and bromination of sulphanilic acid gives 2,4,6-trichloro-and 2,4,6-tribromo-aniline, respectively. However, 4-amino-benzenesulphonamide can be dihalogenated to give the corresponding 2,6-dihalo derivatives [20]. 

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