Inhibitory agents and chemical and mechanisms in the dihalomethane-mediated nitrosation of amines with solid nitrite.

Methylene chloride and certain other dihaloalkanes react efficiently with dissolved secondary amines and, in presence of insoluble sodium nitrite, yield N-nitroso compounds. Mechanistic studies indicate that the intermediates in the nitrosation mixture include the formaldiminium ion, the amine hydrochloride and the diaminomethane (aminal). They also indicate that the formaldiminium ion is by far the most reactive toward sodium nitrite, which probably reacts with the former by nucleophilic attack. Ascorbic acid, ascorbyl palmitate, dehydroascorbic acid, potassium iodide and potassium carbonate inhibited the reaction, whereas alpha-tocopherol, Trolox and sodium ascorbate were found to be ineffective. Ascorbic acid reacted with the secondary amine in a complex fashion. The mode of inhibition probably does not involve reduction of the solid nitrite.