Patent GB-656154-A (GB)
Title: Improvements in the production of saturated aliphatic secondary and tertiary amines
Inventor: OXLEY HORACE FINNINGLEY
IPC: C07C209/08
Filed: 1948-04-14
Abstract: Saturated aliphatic amines containing one or more secondary or tertiary amino groups are made by heating two or more molecular proportions of a saturated halogenated aliphatic hydrocarbon in which no carbon atom carries more than one halogen atom with one molecular proportion of ammonia for each atom of halogen in a molecule of the halogenated hydrocarbon in an aqueous reaction medium containing a base which is more strongly basic than ammonia and the amine or amines formed in the reaction and less strongly basic than sodium hydroxide, the said base being stable, and forming with the hydrogen halide liberated a salt which is stable under the conditions used in the process, the heating being under a pressure sufficient to maintain the reactants and the reaction medium substantially in the liquid phase.  The invention is of particular importance in the preparation of alkylamines in which the alkyl groups contain 1-4 carbon atoms, e.g. di- and tri-methylamine, di- and tri-ethylamine and di- and tri-butylamine.  Preferably the halogenated hydrocarbon is heated with an aqueous or aqueous alcoholic solution of ammonia in the presence of the base.  Preferably higher proportions of halogenated hydrocarbons are used in relation to the ammonia than corresponds to the required amine.  Thus for testing amines from monohalogenated hydrocarbons more than 3, e.g. 3-4 or more, and for secondary amines from monohalogenated hydrocarbons 2-2.8 especially about 2.3-2.7 mol. proportions of halogenated hydrocarbon per mol. of ammonia are used.  Preferred bases are alkaline earth metal hydroxides and magnesium oxide or hydroxide. In the preparation of a tertiary amine preferably at least the theoretical quantity of base to react with the liberated hydrohalic acid is used and advantageously somewhat more, e.g. for each mol. of ammonia at least 1.5 and preferably up to 2 or 2.5 mols. of a di-acid base are used. For a secondary amine the corresponding proportions are up to about 1.3 mols. of a di-acid base per mol. of ammonia although yields may be improved by using less than the theoretical amount, e.g. about 0.25-0.5 mols. per mol. of ammonia.  The amount of base should not be below about one-fifth of that equivalent to the hydrohalic acid. Temperatures instanced are generally above 100 DEG  C., particularly about 110-160 DEG  C., and especially about 120-145 DEG  C.  Vigorous agitation is preferred.  Although the use of chlorinated hydrocarbons is usually preferred, the process may be effected under milder conditions using the corresponding iodine or bromine compounds.  The amines may be recovered from the reaction mixture by conventional methods, e.g. di- and trimethylamine are separated by distillation under high pressure.  In examples aqueous ammonia is autoclaved in the presence of hydrated lime with (1) 80 per cent ethyl chloride (the remainder being ethanol and some ether), at 140 DEG  C. for 8 hours; (2), (3) and (4) 95 per cent ethyl chloride at 140 DEG , 145 DEG  and 120 DEG  C. and for 8 hours, 16 hours and 16 hours respectively, the reaction products then being distilled to a still base temperature of about 150 DEG  C., the distillate acidified with hydrochloric acid and heated to remove e.g. ethanol and ether, cooled, made alkaline with sodium hydroxide and fractionally distilled to yield (1) and (3) mainly triethylamine and (2) and (4) mainly diethylamine.  The Provisional Specification is not limited to the above molar proportions of reactants and states that saturated halogenated aliphatic hydrocarbons are contacted with ammonia in the presence of a moderately strong base, preferably a metal oxide or hydroxide to give secondary or tertiary amines.  Alcoholic solutions of ammonia may also be used.