Halogens Group Hydrochloric acid

As with other groups, halogens can substitute hydrogen in organic compounds containing additional functional moieties such as carboxylic acids to form acid chlorides, e.g. acetyl chloride CH3COCI. These are reactive acidic compounds liberating hydrochloric acid on contact with water. 

Jsomerides of Morphine and Codeine. When morphine is treated with thionyl chloride, phosphorus trichloride or tribromide, the alcoholic hydroxyl group is replaced by the halogen, forming a-chloromorphide and bromomorphide respectively. The former on treatment with concentrated hydrochloric acid is converted into /3-chloromorphide. Schopf and Hirsch have provided evidence that the two are structural isomerides. With the same reagents codeine yields a parallel set of compounds, viz., a- and -chlorocodides, and bromocodide. The chief characteristics of these products may be summarised thus —... 

Also, on replacement of oxalato- or carbonato-group by nitro-, chloro-, or bromo-radicles, brown salts are obtained with acid and sodium nitrite, and violet salts on treatment with concentrated hydrochloric or hydro-bromic acid. The brown nitro-compounds are therefore given a formula with the nitro-groups in the 1-, 2-, or eis-position, and the violet halogen salts the formula with halogen in the m-position. The cis-form may be transformed into the /ra -modification by intramolecular rearrangement. Concentrated hydrochloric acid converts carbonato-tctrammino-cobaltie salts first into violo-salts, and on standing, or on rise of temperature, these pass into the prasco- or I-, 6-salts. 

Photodecomposition of diazonium salts in hydrochloric acid solution results in the introduction of halogen in place of the diazonium group. For example, irradiation of 4-diazoaminodiphenylamine gives 4-chloro-dipheny lamine.271... 

Haloanthraquinones with additional substituents commonly are prepared by direct halogenation of the corresponding anthraquinones in water, hydrochloric acid, sulfuric acid, or organic solvents. Electron-withdrawing substituents, such as sulfonic acid or nitro groups, direct the halogenation to the other nucleus. 

Not only salts of nitrous acids but also nitrous acid itself can replace halogen by the nitro group. This has been discovered by Wuster and Scheibe [194] when they reacted sodium nitrite with bromodimethylaniniline in hydrochloric acid ... 

Acyl selenophenes are chloromethylated at the free a. position (as in sulfonation and halogenation). A second chloromethyl group can be introduced ortho to the first and meta to the acyl group.61 5-Methyl-2-acetylselenophene is chloromethylated in the 4-position.61 When reduced by stannous chloride in hydrochloric acid, 5-chloro-methyl-2-acetylselenophene simply undergoes reduction of the chloromethyl group, and 2-methyl-5-acetylselenophene is formed61 (Scheme 2). 

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