Stabilizer Degradation in Propellants: Identification of Two Isomeric Forms of 2-Nitro-N-nitroso-N-ethylaniline

During the degradation of the propellant stabilizer Centralite I the 2‐nitro‐N‐nitroso‐N‐ethylaniline 2N‐NO‐EA is formed showing two signals in the chromatographic analysis (HPLC) with a 2 : 1 ratio, while the 4‐nitro isomer presents only one signal. This completely unexpected behaviour which interferes with the qualitative and quantitative determination was supposed to be due to the presence of two isomeric forms; however, the existence of two rotameric forms cannot be excluded. A detailed parameter study of the analytical conditions showed that at temperatures of 5 °C the isolation of the two forms should be possible. Preparative chromatography on a RP‐18 column at 5 °C indeed gave fractions with differing percentages of both forms; at room temperature a re‐equilibration to the starting ratio of 2 : 1 was observed.