SPUTTERED AMMONIUM DINITRAMIDE - TANDEM MASS-SPECTROMETRY OF A NEW IONIC NITRAMINE

The recently synthesized ammonium dinitramide (ADN) is an ionic compound containing the ammonium ion and a new oxide of nitrogen, the dinitramide anion (O2N-N-NO2-). ADN has been investigated using high-energy xenon atoms to sputter ions directly from the surface of the neat crystalline solid. Tandem mass spectrometric techniques were used to study dissociation pathways and products of the sputtered ions. Among the sputtered ionic products were NH4+, NO+, NO2+, NO2-, N2O2-., N3O4- and an unexpected high abundance of NO3-. Tandem mass spectra of the dinitramide anion reveal the uncommon situation where a product ion (NO3-) is formed in high relative abundance from metastable parent ions but is formed in very low relative abundance from collisionally activated parent ions. It is proposed that the nitrate anion is formed in the gas phase by a rate-determining isomerization of the dinitramide anion that proceeds through a four-centered transition state. The formation of the strong gas-phase acid, dinitraminic acid (HN3O4), the conjugate acid of the dinitramide anion, was observed to occur by dissociation of protonated ADN and by dissociation of ADN aggregate ions with the general formula [NH4(N(NO2)2)]nNH4+, where n = 1-30.