Molecular processes in electrolyte solutions at microwave frequencies

J. M. G. Barthel, Richard Buchner, K. Bachhuber, H. Hetzenauer, M. Kleebauer, H. Ortmaier
1990 Pure and Applied Chemistry  
T h e microwave dispersion a n d absorption spectra are discussed f o r various p r o t i c a n d aprotic electrolyte solutions a n d t h e i r solvents over large frequency ranges, in general 0.9-90 GHz. Wider frequency ranges a r e covered f o r water (0.9-409 GHz) and f o r methanol, N-methylformamide, md N,N-dmethylformamide ( a l l 0.9-293 GHz). T h e role of insufficient f r equency coverage i s c r i t i c a l l y discussed. Permittivities and relaxation times of t h e u n d e r l y i n
more » ... u n d e r l y i n g relaxation processes are compared f o r electrolyte solutions o f t h e hydrogen-bonding solvents water, methanol and h i g h e r alcohols, formamide, N-methylformamide, a n d t h e dipolar aprotic solvents acetonitrile, propylene carbonate, dimethylsulfoxide, a n d N, N-dimethylformamide. T h e hydrogen-bonding mode a t ~" 1 p s is n o t affected by t h e addition of alkali metal and tetrabutvlammonium salts, in contrast t o t h e bulk and t h e internal relaxation o f t h e Hbonded chains; NHq+ in methanol produces peculiar effects. F o r 1 :1-electrolytes ion-pair formation i s detectable in all solvents o f static p e r m i t t i v i t y below 50; t h e concentration dependence of t h e corresponding relaxation time permits separation i n t o rotational a n d k i n e t i c modes of ion-pair formation a n d decomposition.
doi:10.1351/pac199062122287 fatcat:at6t5tqyvreifdgwmkshkzauuq