Nitrosonium ion reaction with secondary amines

Secondary aryl and alkyl amines react with a nitrosonium ion to form nitrosamines rather than diazonium ions. The mechanism of the reaction is similar to that for the reaction of a primary amine with a nitrosonium ion, except that the reaction stops at the ni-trosamine stage. The reaction stops because a secondary amine, unlike a primary amine, does not have the second proton that must be lost in order to generate the diazonium ion. 

Reaction with Secondary Amines Formation of IV-Nitrosoamines Secondary amines react with the nitrosonium ion to form secondary A-nitrosoamines, sometimes called nitrosamines. 

In water, tertiary amines form quaternary ammonium compounds, e. g. with methyl halogenides. In aqueous solution, secondary (aliphatic and aromatic) amines react with nitrous acid HONO (namely the nitrosonium ion NO ) as already mentioned (reaction 5.217) to generate nitrosamines  

The nitrosonium ion is an extremely strong electrophile and is subject to attack by any amine that is present in solution. An equilibrium is established in which the concentration of nitrosonium ion is rather small. However, as the nitrosonium ion is formed, it can react with the amine that is present. The equihbrium then adjusts to produce more nitrosonium ion. The outcome of the reaction depends on whether the amine is primary or secondary. We will explore these possibdities separately, beginning with secondary amines. 

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