Nitrosation of Amines

These reactions are referred to as nucleophilic acyl substitution.

NITROSATION OF AMINES

This involves the addition of a primary amine with nitrous acid (HNO2). The reaction will yield a diazonium ion (RNN+) plus water. It can also involve the nitrosation of a secondary amine to yield N-nitrosamine, which is RR’NNO plus water. This is demonstrated in figure 108:

Figure 108.

This type of reaction involves sodium nitrite and an acid, yielding nitrous acid. These can be mixed with aryl amines, in particular to give aryl diazonium salts, which are used to make substituted benzene molecules. Nitrous acid will lose water to make an NO (nitrosyl) cation, which is the actual reactant in this reaction. When this is done with an aryl amine, it yields and aryl-NN molecule (which is highly unstable) that gives off N2 gas and an aryl plus cation, which can easily be substituted to make a substituted benzene group.

There are many things that can be made by making first an aryl diazonium ion. It can be mixed with copper chloride or copper bromide to make benzyl chloride or benzyl bromide, respectively. It can be mixed with phenol to make an azo compound. Any halide, in fact, can be added to the aryl diazonium ion to make a halogenated benzene compound, and phenol itself can be made because of the carbo-cation made from the

aryl diazonium molecule. Copper cyanide can be mixed with the aryl diazonium ion to make an aryl cyanide compound. This addition of copper cyanide or copper halide to make the substituted benzene compound is referred to as a “Sandmeyer reaction”.