Electron paramagnetic resonance spectroscopic study of nitroxide radicals formed from oximes

Abstract

The addition of hydroxyl radicals to each of the oximes, acetaldoxime, acetoxime, and 2,3-butanedione monoxime, has been studied by mixing titanous chloride, hydrogen peroxide, and the oxime in a n aqueous continuous-flow system. I n each case a p-hydroxy nitroxide (functional structure )c(oH)-NH-0.) is formed. I n confirmation of these results, amino and hydroxymethyl radicals we; e added to the oximes using similar procedures to give in each case the radicals of functional structure >c(NH,)-NH-0. and )C(CH~OH)-NH-o., respectively. Attempts to add methyl radicals, prepared by the reaction betwGen titanous chloride and t-butyl hydroperoxide, to these oximes gave no observable products save the methyl radicals. However, use of titanous chloride and peracetic acid gave results consistent with the addition of hydroxyl radicals. The addition of hydroxyl radicals to the oxime-0-methyl ethers of acetaldehyde and acetone gave radicals of functional structure 'c(oH)-N-0-CH, / (JaNl, ca. 14 G ; a,,0CH3~, ca. 3 G ) which have not previously been identified unambiguously. On the assumption that JQNl = lQHNH = 23 G in all these radicals, pNn has been calculated and used to obtain a value for lQHO H~I of ca. 11 G whlch is within the range of other estimates in the literature.

Quinone-sensitized Steady-state Photolysis of Acetophenone Oximes Under Aerobic Conditions: Kinetics and Product Studies†

“…The use of oximes and related compounds in pesticides (1, 2) and drugs (3–6) has increased in recent years, leading to a larger availability in the environment (7) and an increased risk of uptake by organisms. Detoxification of such xenobiotics typically involves oxidative pathways (8), which, in the case of oximes, can result in the formation of reactive oxygen species (ROS) such as iminoxyl radicals (9–16). Little is known about these reactive intermediates.…”

Electron paramagnetic resonance spectroscopic study of radicals derived from glycine, dl-α-alanine, and β-alanine in aqueous solution

“…McConnell Q-parameter values QHCH, QHCCH3, QNN, and QHNH2 shown in Table 3, calculated with the use of the following equations The Q-parameter values listed in Table 3 are in the range obtained for aliphatic radicals (9,30,40,41 48,1970 This value is not within the range which has been reported already for this parameter, i.e., ca. 7-21 G (30).…”

“…1.3 and 1.4 G, respectively. This assumes that QHoH and QHoCH3 are approximately equal, although there is considerable uncertainty about the sizes of these Q-parameters (30). The assignment is strengthened by the observation that the size of the doublet behaves in the manner expected for an interaction with an exchangeable proton, i.e.…”

The Photooxidative Degradation of Polypropylene. Part II. Photostabilization Mechanisms

“…Nitroxides have also been shown to quench the excited singlet states of polynuclear aromatic compounds at close to the diffusion-controlled rate Table 1) [20]. This effectiveness might again result from radical scavenging, as oldmes are known to react with alkoxy radicals [96] and -OH radicals [97]. This reaction produces iminoxy or nitroxide radicals, which can in turn scavenge other alkoxy radicals: …”