The reaction of ethoxyquin (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline) with nitrous acid

The reaction of ethoxyquin (6-ethoxy-1,2-dihydro-2,2,4-trimethylquinotine) with acidified sodium nitrite solution over a short period at room temperature gives the unstable 1-nitroso derivative together with smaller amounts of the 8-nitro derivative and a quinone imine which has lost the ethyl group. The 8-nitroso derivative is observed fleetingly as a very readily oxidised intermediate. On being kept on silica gel the 1-nitroso derivative is partly transformed into the 8-nitro derivative and ethoxyquin itself, but the main product is the quinone imine. The crystal structures of 8-nitroethoxyquin (2) and of 6-acetoxy-1,2-dihydro-2,2,4-trimethylquinoline (7), the product of reduction–acetylation of the quinone imine, have been determined by X-ray analysis.