title: Hydrogen atom formation by ultrasound in D2O solutions of nitrone spin traps.
abstract: To elucidate the mechanism of ultrasonically induced H atom formation in D2O solutions of nitrone spin traps, alpha-phenyl-N-tert-butylnitrone (PBN) and alpha-(4-pyridyl-1-oxide)- N-tert-butylnitrone (POBN) were exposed to 50 kHz ultrasound in the presence of Ar, and the ratio of the ESR signal of the H-spin adduct to that of the D-spin adduct (H/D ratio) was examined. The H/D ratio increased with the concentration of the spin traps. The magnitude of the H/D ratios correlates with the hydrophobicity of the spin traps. The H/D ratios for the more hydrophobic spin trap, PBN, are larger than those for POBN at all concentrations. Xenon, which has a lower thermal conductivity than argon, was employed for creating higher final temperatures of the cavitation bubbles. For the less hydrophobic spin trap POBN the H/D ratio is lower for xenon than for argon. A similar result was found for PBN at lower concentrations. These results show that the H adducts of PBN and POBN are formed from the spin traps or their decomposition products by homolytic scission of C-H bonds due to pyrolysis.
authors.affiliation: Radiation Oncology Branch, National Cancer Institute, Bethesda, Maryland 20892.
authors.forename: T
authors.initials: T
authors.lastname: Kondo
authors.forename: P
authors.initials: P
authors.lastname: Riesz
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003497:Cyclic N-Oxides; D003903:Deuterium / Q000032:analysis* / Q000528:radiation effects; D017666:Deuterium Oxide; D004578:Electron Spin Resonance Spectroscopy; D005720:Gamma Rays; D006859:Hydrogen / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D009589:Nitrogen Oxides / Q000032:analysis*; D011725:Pyridines; D013113:Spin Labels; D014465:Ultrasonics; D014867:Water / Q000032:analysis* / Q000528:radiation effects; D014978:Xenon
chemical_list: D003497:Cyclic N-Oxides; D009589:Nitrogen Oxides; D011725:Pyridines; D013113:Spin Labels; C043438:alpha-(4-pyridyl-1-oxide)-N-tert-butylnitrone; C015388:nitrones; D014867:Water; D014978:Xenon; C029217:phenyl-N-tert-butylnitrone; D006859:Hydrogen; D003903:Deuterium; D017666:Deuterium Oxide