Preparation of Amines by Ammonolysis

Introduction, Amines are organic derivatives of ammonia, with one, two, or three hydrogen atoms replaced by an organic radical. The three types of amines, primary (RNHj), secondary (RjNH), and tertiary (R3N), may be prepared by the reaction of mono-halides with ammonia. In the case of reactive halides, like methyl iodide, the reaction proceeds to the formation of the quaternary salt— tetramethylammonium iodide  

When one mole of methyl iodide and four moles of ammonia are used, the formation of primary, secondary, and tertiary amines proceeds rapidly, so that within two minutes the formation of tetramethylammonium iodide assumes the dominant role of the reaction. About seventy-five per cent of the methyl iodide is converted to the quaternary salt, while the remainder forms a mixture of the three amines. The formation of the quaternary salt can be inhibited to a large extent by the addition of an ammonium salt, such as ammonium nitrate, which reacts with the free amino group of the amine to form the ion  

Since the amino group is blocked, the formation of secondary and tertiary amines is inhibited. 

The ammonolysis of the alkyl monohalides suffers from the difficulties involved in the separation of the mixture of amines. The reaction is best carried out by adding the halide to a saturated (15-20%) alcoholic solution of ammonia. If a greater proportion of primary amine is desired, 9-10 moles of ammonia and one mole of halide are allowed to stand at room temperature for several days, or ammonium nitrate is added and the amomit of ammonia is reduced. The addition of salt reduces the solubility of the halide 

If secondary and tertiary amines are desired, only 2 to 3 moles of ammonia are used. Aqueous ammonia does not react to any extent at room temperature, owing to the immiscibility of halide and water. Industrially, aqueous ammonia is used and heated in an autoclave under pressure. Tertiary halides, as, for example, tert-butyl and tert- m.y bromides, do not yield amines, but yield olefines almost exclusively. The object of the present experiment is to illustrate the ammonolysis of alkyl halides. The ammonolysis of aryl halides cannot be easily accomplished in the laboratory, as it involves the use of high pressure, and temperatures of about 200°. Industrially the method is practical. 

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