Use of X-band EPR to follow the reaction between various nucleophilic compounds and 2-methyl-2-nitrosopropane (MNP)

Abstract

Continuous wave X-band EPR spectroscopy was used as an analytical tool to follow the formation of nitroxide radicals after the reaction between various nucleophiles and 2-methyl-2-nitrosopropane (MNP). The addition of amines or of trihalogeno-acetic acids onto the nitroso moiety was found to depend on experimental parameters such as exposure to white light or the nature of the solvent, while no nitroxide adducts were ever detected when alcohols or weak carboxylic acids were used. In contrast to results previously obtained with cysteine, the reaction of ten standard amino acids (Gly, Lys, Arg, His, Trp, Ser, Thr, Tyr, Asp and Glu) on MNP never led to an EPR observable adduct, further confirming the particular reactivity of this nitroso compound towards thiols.