Accession Number : ADA294733

Title :   Dissociative Ionization of Methylated Hydrazines.

Descriptive Note : Technical rept.,

Corporate Author : AEROSPACE CORP EL SEGUNDO CA TECHNOLOGY OPERATIONS

Personal Author(s) : Brady, B. B. ; Syage, J. A.

PDF Url : ADA294733

Report Date : 30 JAN 1995

Pagination or Media Count : 24

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

Descriptors :   *HYDRAZINES, *DIMETHYLHYDRAZINES, *METHYL RADICALS, *DISSOCIATION, IONS, DETECTION, HIGH RATE, FRAGMENTATION, THRESHOLD EFFECTS, GRAPHS, QUADRUPOLE MOMENT, HIGH RESOLUTION, CHEMICAL COMPOSITION, HIGH ENERGY, PROPELLANTS, FUELS, ELECTRON ENERGY, ASYMMETRY, ELECTRON IMPACT SPECTRA, RESPONSE, THERMOCHEMISTRY, CROSS SECTIONS, KINETIC ENERGY, YIELD, IONIZATION, CHEMICAL EQUILIBRIUM, PLOTTING, MASS SPECTROMETRY, ACTIVATION ENERGY.

Subject Categories : Organic Chemistry
      Physical Chemistry
      Atomic and Molecular Physics and Spectroscopy

Distribution Statement : APPROVED FOR PUBLIC RELEASE