Reactions and characterisation of aliphatic amines

The more important reactions of aliphatic amines, which will assist in their detection, are given below. 

Salts of amines are generally soluble in water. Upon treatment with 10 per cent, sodium hydroxide solution, the amine will separate if it is insoluble or sparingly soluble in water if the amine is water-soluble, it can be partially volatilised by gentle warming and its presence will be suggested by a characteristic odour. 

If desired, the alcohol may be identified as the 3 5-dinitrobenzoate (Section 111,27) it is then best to repeat the experiment on a larger scale and to replace the dilute hydrochloric acid by dilute sulphuric acid. It must, however, be pointed out that the reaction is not always so simple as indicated in the above equation. Olefine formation and rearrangement of the alcohol sometimes occur thus n-prop3 lamine yields n-propyl alcohol, isopropyl alcohol and propylene. 

When the reaction is over, add- concentrated hydrochloric acid to decompose the tsocyanide and pour it away after the odour is no longer discernible. The test is extremely dehcate and will often detect traces of primary amines in secondary and tertiary amines it must therefore be used with due regard to this and other factors. 

To 5 ml. of water add 1-2 drops of the amine if the amine does not dissolve, add a drop or two of concentrated hydrochloric acid. Add 0-5-1 ml. of this amine solution to 2-3 ml. of the reagent an almost immediate precipitate indicates the presence of a primary amine. A slight turbidity indicates the presence of a primary amine as an impurity. (Primary aromatic amines generally require 2-3 minutes for the test. Urea and other amides, as well as amino acids, do not react.) 

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Primary aliphatic amines, 413 crystalline derivatives of, 424 reactions of, 420, 1072 table of, and derivatives of, 424 Primary aromatic amines, 539 crystalline derivatives of, 652 reactions and characterisation of, 648, 1073 ... 

The donor-acceptor complexes formed between electron acceptors (such as iodine or tetracyanoethylene) and electron donors (such as aliphatic amines or aromatic hydrocarbons) have, been extensively studied from various points of view -spectroscopic 5 structural and thermodynamic (3). Kinetic investigation has lagged behind, because the reactions are extremely fast and the equilibrium constants small the rate constant of one such reaction had been measured by means of our microwave apparatus (without the recent improvements), at -83 C (U). We have now determined rate constants, in 1-chlorobutane, as solvent for the reactions of zinc tetraphenyl-porphyrin with pyridine and 2-methyl pyridine, which have been well characterised by spectrophotometric methods (5, 6). They are less than the diffusion-controlled value by an order of magnitude. Further investigations are in progress. 

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