Studying Ionization and Decomposition Mechanism of Alkyl Dinitrites by Mass Spectrometry

Alkyl dinitrites with two functional groups, R2C(ONO)(CH2)(n)C(ONO)R-2, can easily produce alkoxy radicals and nitric oxide in the atmosphere. Their high activity has led to issues such as photochemical air pollution and the greenhouse effect. Hence, unraveling the decomposition mechanism of alkyl dinitrites is of great significance in understanding their photochemical and thermochemical roles in the atmosphere. In this work, the dissociation process of six alkyl dinitrites was investigated by mass spectrometry under the electron impact energy of 70 eV. Our results indicated that the ruptured fragments had characteristic directivity for the structures of alkyl dinitrites. We detected not only the NO+ fragment ion, due to the common breakage of O-NO bond, but also R2C(ONO)(+) resulting from the breakage of a C-C bond in the electron ionization mass spectra. The dissociation mechanism of alkyl dinitrites in which the O-NO or C-C bond directly dissociates is different from photolysis and pyrolysis.