Dissociative Ionization of Methylated Hydrazines.
Abstract
The dissociation of methylated hydrazine ions is observed to undergo extensive fragmentation and rearrangement leading to many fragments that have the same nominal mass, but differ in chemical composition by an N versus CH2 moiety. In earlier work, we measured absolute ionization cross section for hydrazine and methylhydrazine (MMH) dissociative ionization using a high throughput time-of-flight mass spectrometer that had excellent detectability of high kinetic energy ions, but only moderate mass resolution (0.1 amu). Here we employ high resolution quadrupole detection (0.005 amu) to distinguish ion fragments of the same nominal mass for MMH and unsymmetrical dimethylhydrazine (UDMH). The ratios of these close lying fragment masses are measured for different electron impact energies and explained in terms of thermochemical thresholds and fragmentation mechanisms. The methyl groups account for complex reaction mechanisms. A high yield is observed for NH dissociation induced by a 1, sigmatropic hydride shift and for CH4 dissociation formed by a 1,2 elimination. Ion yield vs. thermochemical threshold plots are compared to model equilibrium curves and allow an estimate of the energy deposited by electron impact ionization and an assessment of how dissociative ionization differs for ambient vs. jet-cooled hydrazines. Departures of ion yield from the equilibrium curve are used to identify fragmentation reactions that involve large activation energies or unusual mechanisms. jg
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 30, 1995
- Accession Number
- ADA294733
Entities
People
- B. B. Brady
- J. A. Syage
Organizations
- The Aerospace Corporation