DIFFUSE REFLECTANCE INFRARED FOURIER-TRANSFORM (DRIFT) SPECTROSCOPIC STUDY OF ADSORBED HYDRAZINES

Diffuse reflectance spectroscopy of fuel hydrazines adsorbed on silica, silica-alumina, alumina and ferric oxide surfaces indicates that the primary surface-hydrazine interaction is hydrogen bonding. Hydrazine, on adsorption to a deuterated silica surface, undergoes a rapid H/D exchange with deuterated surface silanol (Si-OD) groups. Adsorption equilibria are rapidly established at room temperature. Monomethylhydrazine and 1,1-dimethylhydrazine are similarly adsorbed. On adsorption, the C-H stretching and methyl deformation modes of the methylhydrazines are shifted to higher frequencies by 10-20 cm-1. These shifts are postulated to be due to changes in the lone-pair electron-density on the adjacent nitrogen-atom. From a linear relationship of the electronegativities and deformation frequencies it is estimated that adsorption results in a 5% increase in electronegativity of the H-bonded atom.