Radiation Sensitization Reactions of N-Ethylmaleimide with Model Compounds

TLDR: The reaction of N-ethylmaleimide and NEMA with OH radicals and H atoms results in NEMA, which is produced from the hydrolysis of NEM at pH > 7.

Abstract: The reaction of $e_{{\rm aq}}^{-}$ , OH radicals and H atoms with N-ethylmaleimide (NEM) and N-ethylmaleamic acid (NEMA, which is produced from the hydrolysis of NEM at pH > 7) were investigated in aqueous solutions. The reaction rate constants, the transient optical absorption spectra and the decay kinetics of the resulting intermediates were obtained. The free radical sensitization reactions of NEM with model compounds were followed by pulse radiolysis. A number of organic free radicals were found to react with NEM by an electron transfer process (oxidation of free radicals) to produce $\cdot {\rm NEM}^{-}$ , and/or by addition to NEM. NEMA, being a poorer oxidizing agent, does not appear to undergo most of these reactions. Electron adducts (e.g., radical anions of pyrimidine bases) were shown to transfer an electron to NEM. Solutes with redox potentials higher than that of NEM, such as menadione and oxygen, were found to be good electron acceptors from ...