Kernresonanz-Emissionslinien während rascher Radikalreaktionen

Abstract

For the detection of unstable intermediates during rapid chemical reactions an experimental technique has been developed which allows tracing of reactions with reaction times of minutes or seconds by nuclear magnetic resonance spectroscopy. By this technique series of NMR spectra were taken during thermal decomposition of peroxides and azo-compounds, and the following unexpected effect was observed: During some reactions the proton resonance lines of reaction products appear intermediately in emission instead of absorption. The emission lines in the decomposition reactions of dibenzoylperoxide and di-p-chlorbenzoylperoxide are treated in detail, and are shown to be due to benzene and chlorobenzene molecules formed in the reactions. Obviously these molecules are formed initially with a negative spin polarization of their proton spin systems which is assumed to be a consequence of a chemically induced dynamic nuclear polarization.