OXIDATIVE-DEGRADATION OF ETHYLENETHIOUREA (ETU) AND ETU PROGENITORS BY HYDROGEN-PEROXIDE AND HYPOCHLORITE

The mechanism of hydrogen peroxide and hypochlorite mediated oxidations of ethylenethiourea (ETU) was reinvestigated. Evidence is presented which suggests that, in water, a radical dissociation of the intermediate 2-imidazolin-2-yl sulfinate (ETU-O2) and subsequent trapping by solvent results in 2-imidazoline hydrosulfite which is, in turn, rapidly oxidized to 2-imidazoline hydrosulfate. Alternately, ETU-O2may be oxidized to 2-imidazolin-2-yl sulfonate (ETU-O3) in low yield. In 1% bicarbonate solution ethyleneurea (EU) is the major product of ETU oxidation whether hypochlorite or hydrogen peroxide is used as the oxidant. A mechanism for the oxidations of ETU that is consistent with radiotracer and spectroscopic studies is proposed. Although ethylenebis(dithiocarbamate) (EBDC) formulations are degraded by hydrogen peroxide, this oxidant is less effective than hypochlorite due to oxidant destruction by metal cations in the formulation. Whereas Jaffe's base [l-(2ʹ-imidazolin-2ʹ-yl)-2-imidazolidinethione], which is a potential source of ETU, is rapidly inactivated by hypochlorite, it reacts only slowly with aqueous hydrogen peroxide to form the corresponding sulfenate. © 1979, American Chemical Society. All rights reserved.