Diazotisation aliphatic amines

The determination of primary amines on the macro scale is most conveniently carried out by titration in non-aqueous solution (Section 10.41), but for small quantities of amines spectroscopic methods of determination are very valuable. In some cases the procedure is applicable to aromatic amines only, and the diazotisation method described for determination of nitrite (Section 17.38) can be adapted as a method for the determination of aromatic primary amines. On the other hand, the naphthaquinone method can be applied to both aliphatic and aromatic primary amines. 

The simple primary amines of the aliphatic series, then, do not form diazo-compounds because the reaction which would le, d to their formation only occurs at a temperature at which they are destroyed. The reactivity of the NH2-group can, however, be increased by a neighbouring carbonyl group. Thus we come to the case of the esters of the a-amino-carboxylic acids and of the a-amino-ketones. The ethyl ester of glycine can be diazotised even in the cold the diazo-compound which does not decompose under these conditions undergoes stabilisation by elimination of water and change into ethyl diazoacetate ... 

With nitrous acid, primary amines are diazotised (equation 58), secondary amines undergo iV nitrosation (section II.C.2.e), and tertiary aliphatic or alicyclic amines fail to react while tertiary aromatic amines may undergo C-nitrosation. 

Alkyl nitrites are useful mild reagents for diazotisation and deamination in organic solvents. In benzene, aniline is readily deamina-ted at elevated temperatures by these reagents and the product reacts with the solvent to form biphenyl in high yield . Nitrosonium tetrafluoroborate (NO+BF ") also reacts readily with both aliphatic and aromatic amines in dry organic solvents . 

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