ESR SPECTRAL STUDY OF FREE-RADICAL FORMATION DURING THE PYROLYSIS OF HYDROXYAMINO ACIDS

Relatively stable free radicals, formed by pyrolysis of DL-serine, DL-threonine and DL-tyrosine over the temperature range 200-600-degrees-C, during reaction periods lasting for between 2 and 180 min, were identified by Electron Spin Resonance ESR spectroscopy. The ESR spectra, which showed broad singlets in all examined cases, suggest that the free radicals were different types of polycondensation species. The concentrations of free radicals formed, measured as the intensities of absorption of the spectral lines, depended on the applied temperatures, the duration of pyrolysis and the structure of the examined amino acids.