Reactivity of Oxygen Radicals [HO•, RO•, HOO•, ROO-, and RC(O)O•]

1992 ◽  
Author(s):  
Donald T. Sawyer ◽  
R. J. P. Williams
Keyword(s):  
Oxygen Atom ◽  
Hydroxyl Radical ◽  
Gas Phase ◽  
Oxygen Radicals ◽  
Oxygen Radical ◽  
Superoxide Ion ◽  
Radical Reactivity ◽  
The Family ◽  
Hydrocarbon Substrates

Oxygen radicals are defined as those molecules that contain an oxygen atom with an unpaired, nonbonding electron (e.g., HO·). Although triplet dioxygen (·O2·) and superoxide ion (O2 - ·) come under this definition, their nonradical chemistry dominates their reactivity, which is discussed in Chapters 6 (·O2·) and 7 (O2-·). The hydroxyl radical (HO·) is the most reactive member of the family of oxygen radicals [HO·, RO·, ·O·, HOO·, ROO·, and RC(O)O·], and is the focus of most oxygen radical research. In the gas phase the dramatic example of oxygen radical reactivity with hydrocarbon substrates is combustion, which is initiated by HO· (or RO· or MO·) and propagated by ·O2· and ·O·.

scholarly journals Role of (H2O)n (n = 1–2) in the Gas-Phase Reaction of Ethanol with Hydroxyl Radical: Mechanism, Kinetics, and Products

ACS Omega ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 5805-5817 ◽  
Author(s):  
Li Xu ◽  
Narcisse T. Tsona ◽  
Shanshan Tang ◽  
Junyao Li ◽  
Lin Du
Keyword(s):  
Hydroxyl Radical ◽  
Gas Phase ◽  
Radical Mechanism ◽  
Phase Reaction ◽  
Gas Phase Reaction

Conversion of xanthine dehydrogenase to oxidase in ischemic rat intestine: a reevaluation

1988 ◽  
Vol 254 (5) ◽  
pp. G768-G774 ◽  
Author(s):  
D. A. Parks ◽  
T. K. Williams ◽  
J. S. Beckman
Keyword(s):  
Small Intestine ◽  
Oxygen Radicals ◽  
Total Activity ◽  
Xanthine Dehydrogenase ◽  
Oxygen Radical ◽  
Morphological Evidence ◽  
Cellular Injury ◽  
Rat Intestine ◽  
Entire Small Intestine ◽  
Ischemic Intestine

Oxygen radicals derived from xanthine oxidase (XO) are important mediators of the cellular injury associated with reperfusion of ischemic intestine, stomach, liver, kidney, and pancreas. XO exists in nonischemic tissue predominantly as xanthine dehydrogenase (XDH) and converts to oxygen radical-producing XO with ischemia. Grinding intestine under liquid nitrogen and placing the powder in phosphate buffer (pH 7.0) containing thiol reductants and protease inhibitors adequately preserved total XDH + XO activity and the percentage in the oxidase form (%XO) for 24 h. Total activity in nonischemic intestine ranged from 374 nmol.min-1.g-1 in duodenum to 138 nmol.min-1.g-1 in ileum, while XO activity was approximately 19% of total activity throughout the entire small intestine. The rate of XDH conversion to XO during normothermic ischemia varied only slightly throughout the intestine, increasing 13% per hour to 34, 46, and 61% XO after 1, 2, and 3 h of ischemia, respectively. Our results contrast with previous reports where XDH conversion to XO occurred within 60 s ischemia but are consistent with physiological and morphological evidence of ischemic injury and provide further support for involvement of XO in intestinal injury associated with ischemia.

scholarly journals Modeling nitrous acid and its impact on ozone and hydroxyl radical during the Texas Air Quality Study 2006

2012 ◽  
Vol 12 (2) ◽  
pp. 5851-5880 ◽  
Author(s):  
B. H. Czader ◽  
B. Rappenglück ◽  
P. Percell ◽  
D. W. Byun ◽  
F. Ngan ◽  
...  
Keyword(s):  
Air Quality ◽  
Hydroxyl Radical ◽  
Gas Phase ◽  
Nitrous Acid ◽  
Organic Materials ◽  
Optical Absorption Spectroscopy ◽  
Ozone Formation ◽  
Mixing Ratios ◽  
Quality Study ◽  
Mist Chamber

Abstract. Nitrous acid (HONO) mixing ratios for the Houston metropolitan area were simulated with the Community Multiscale Air Quality (CMAQ) model for an episode during the Texas Air Quality Study (TexAQS) II in August/September 2006 and compared to in-situ MC/IC (mist-chamber/ion chromatograph) and long path DOAS (Differential Optical Absorption Spectroscopy) measurements at three different altitudes. Several HONO sources were accounted for in simulations, such as gas phase formation, direct emissions, nitrogen dioxide (NO2*) hydrolysis, photo-induced formation from excited NO2* and photo-induced conversion of NO2 into HONO on surfaces covered with organic materials. Compared to the gas-phase HONO formation there was about a tenfold increase in HONO mixing ratios when additional HONO sources were taken into account, which improved the correlation between modeled and measured values. Concentrations of HONO simulated with only gas phase chemistry did not change with altitude, while measured HONO concentrations decrease with height. A trend of decreasing HONO concentration with altitude was well captured with CMAQ predicted concentrations when heterogeneous chemistry and photolytic sources of HONO were taken into account. Heterogeneous HONO production mainly accelerated morning ozone formation, albeit slightly. Also HONO formation from excited NO2 only slightly affected HONO and ozone (O3) concentrations. Photo-induced conversion of NO2 into HONO on surfaces covered with organic materials turned out to be a strong source of daytime HONO. Since HONO immediately photo-dissociates during daytime its ambient mixing ratios were only marginally altered (up to 0.5 ppbv), but significant increase in the hydroxyl radical (OH) and ozone concentration was obtained. In contrast to heterogeneous HONO formation that mainly accelerated morning ozone formation, inclusion of photo-induced surface chemistry influenced ozone throughout the day.

Multivariate modelling of the rate constant of the gas-phase reaction of haloalkanes with the hydroxyl radical

1991 ◽  
Vol 109-110 ◽  
pp. 307-325 ◽  
Author(s):  
Maria Livia Tosato ◽  
Claudio Chiorboli ◽  
Lennart Eriksson ◽  
Jorgen Jonsson
Keyword(s):  
Hydroxyl Radical ◽  
Gas Phase ◽  
Rate Constant ◽  
Phase Reaction ◽  
Gas Phase Reaction ◽  
Multivariate Modelling

scholarly journals Probing ‘Spin-Forbidden’ Oxygen-Atom Transfer: Gas-Phase Reactions of Chromium−Porphyrin Complexes

2010 ◽  
Vol 132 (12) ◽  
pp. 4336-4343 ◽  
Author(s):  
Maria Elisa Crestoni ◽  
Simonetta Fornarini ◽  
Francesco Lanucara ◽  
Jeffrey J. Warren ◽  
James M. Mayer
Keyword(s):  
Oxygen Atom ◽  
Gas Phase ◽  
Atom Transfer ◽  
Oxygen Atom Transfer ◽  
Gas Phase Reactions

scholarly journals Theoretical Study of Sigmatropic Rearrangement of Cycloprop-2-en-1-ol and its Fluorine Derivatives: Pericyclic or Pseudopericyclic Character from NICS and LLPE

2019 ◽  
Vol 31 (3) ◽  
pp. 597-601
Author(s):  
A. Sangeetha ◽  
A. Thaminum Ansari ◽  
Jebakumar Jeevanandam ◽  
S. Jayaprakash
Keyword(s):  
Oxygen Atom ◽  
Gas Phase ◽  
Energy Barrier ◽  
Fluorine Atom ◽  
Theoretical Study ◽  
Lone Pair ◽  
Sigmatropic Rearrangement ◽  
Nucleus Independent Chemical Shift ◽  
Lone Pair Electron ◽  
Rearrangement Reaction

Sigmatropic rearrangement reaction of cycloprop-2-en-1-ol and its fluorine derivatives has been studied theoretically in gas phase and its energy barrier has been calculated. Nucleus-independent chemical shift (NICS) shows sigmatropic rearrangement of cycloprop-2-en-1-ol is pericyclic in nature whereas fluorine derivatives show pseudopericyclic and pericyclic nature. Substitution of fluorine atom at ring is found to increase the energy barrier for –OH migration, while substitution at oxygen atom reduces the barrier. To know the involvement of lone pair of electrons during the reaction, lone pair electron present on oxygen atom is locked by hydrogen bonding. CR-CCSD(T)/6-311+G** levels are used to study the reactions more accurately.

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