Homolytic Scission of Interunitary Bonds in Lignin Induced by Ultrasonic Irradiation of MWL Dissolved in Dimethylsulfoxide

Holzforschung ◽  
2000 ◽  
Vol 54 (4) ◽  
pp. 357-364 ◽  
Author(s):  
Aki Yoshioka ◽  
Teruyuki Seino ◽  
Masayoshi Tabata ◽  
Mitsuo Takai
Keyword(s):  
Ultrasonic Irradiation ◽  
Spin Trap ◽  
Spin Trapping ◽  
Spin Adduct ◽  
Dmso Solution ◽  
Picea Jezoensis ◽  
Spin Resonance ◽  
Spin Trapping Technique ◽  
Secondary Carbon ◽  
Stable Nitroxide

SummaryAn electron spin resonance (ESR) method combined with a spin trapping technique was applied to trap and characterize unstable radicals which were generated by ultrasonic irradiation of the dimethylsulfoxide (DMSO) solution of a softwood, Yezo Spruce (Picea jezoensiscarr.) lignin. It was found that an unstable secondary carbon radical, ~CH • in the solution was trapped as the stable nitroxide spin adduct when the DMSO solution was subjected to ultrasonic irradiation in the presence of a spin trapping reagent: 2,4,6-tri-tert-butylnitrosobenzene (BNB) at 50°C for 30 min. This means that the alkyl phenyl ether bonds, ~CH-O-phenyl, known as interunitary bonds in lignins were homolytically cleaved by the ultrasonic irradiation, although the phenoxy radical Ph-O •, called guaiacoxy radical, i.e. the counter radical of the secondary carbon radical, was not trapped by the BNB spin trap. This suggests that the trapping of the guaiacoxy radical, having a methoxy group in anortho-position, by the BNB molecule, carrying two bulky butyl groups in theortho-positions, is sterically hindered.

Utilisation des pièges à radicaux en vue de mettre en évidence des intermédiaires dans la photolyse de complexes contenant une liaison CoIII—C

1982 ◽  
Vol 60 (12) ◽  
pp. 1402-1413 ◽  
Author(s):  
Philippe Maillard ◽  
Charles Giannotti
Keyword(s):  
Free Radicals ◽  
Hydrogen Atom ◽  
Spin Trap ◽  
Spin Trapping ◽  
Spin Adduct ◽  
Efficient Manner ◽  
Solvent Cage ◽  
Selective Deuteration ◽  
Equatorial Ligand ◽  
Spin Trapping Technique

Using the spin trapping technique with 5,5′-dimethyl 1-pyrroline N-oxide (DMPO), phenyl-N-tert-butyl nitrone (PBN), nitrosodurene (ND), and α-4-pyridyl 1-oxide N-tert-butl nitrone (4-POBN), or their mixtures, we have been able to detect two types of radicals, one is a hydrogen atom spin adduct and the other is the corresponding alkyl of the alkylcobaloximes, salens or cobalamines.By the use of selective deuteration and the preparation of the benzyl bis(diphenylglyoximato)-pyridinato cobaloxime, we have shown that the spin trapped hydrogen atom comes from the chelated hydrogen of the dimethylglyoximato anion of the equatorial ligand of CoIII complexes. Using a mixture of two spin traps gives rise to an esr spectrum containing, at the same time, the hydrogen atom and alkyl spin adducts.To explain such an efficient spin trapping reaction while the homolysis is in competition with a β-elimination process, it should be postulated that the photolysis of such compounds proceeds through a solvent cage environment. This hypothesis explains the strong influence of solvents on the nature of the free radicals trapped. Also the spin trap diffuses in the solvent cage, and is able to trap in a very efficient manner any free radicals occurring in the solvent cage. The excited CoIII complexes and the spin trap in the solvent cage behave like an exciplex, which could explain the spin trapping of the hydrogen atom.

scholarly journals Estimation of the Postmortem Duration of Mouse Tissue by Electron Spin Resonance Spectroscopy

2011 ◽  
Vol 2011 ◽  
pp. 1-11
Author(s):  
Shinobu Ito ◽  
Tomohisa Mori ◽  
Hideko Kanazawa ◽  
Toshiko Sawaguchi
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Electron Spin ◽  
Spin Trap ◽  
Detection Sensitivity ◽  
Mouse Tissue ◽  
Spin Adduct ◽  
Simple Method ◽  
Oxidation Stress ◽  
Spin Resonance

Electron spin resonance (ESR) method is a simple method for detecting various free radicals simultaneously and directly. However, ESR spin trap method is unsuited to analyze weak ESR signals in organs because of water-induced dielectric loss (WIDL). To minimize WIDL occurring in biotissues and to improve detection sensitivity to free radicals in tissues, ESR cuvette was modified and used with 5,5-dimethtyl-1-pyrroline N-oxide (DMPO). The tissue samples were mouse brain, hart, lung, liver, kidney, pancreas, muscle, skin, and whole blood, where various ESR spin adduct signals including DMPO-ascorbyl radical (AsA∗), DMPO-superoxide anion radical (OOH), and DMPO-hydrogen radical (H) signal were detected. Postmortem changes in DMPO-AsA∗and DMPO-OOH were observed in various tissues of mouse. The signal peak of spin adduct was monitored until the 205th day postmortem. DMPO-AsA∗in liver (y=113.8–40.7 log (day),R1=-0.779,R2=0.6,P<.001) was found to linearly decrease with the logarithm of postmortem duration days. Therefore, DMPO-AsA∗signal may be suitable for detecting an oxidation stress tracer from tissue in comparison with other spin adduct signal on ESR spin trap method.

An electron spin resonance spin trapping investigation of azide oxidation on TiO2 powder suspensions

1988 ◽  
Vol 66 (1) ◽  
pp. 76-80 ◽  
Author(s):  
Andrea Maldotti ◽  
Rossano Amadelli ◽  
Vittorio Carassiti
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Spin Trapping ◽  
Tio2 Powder ◽  
Aqueous Alkaline Medium ◽  
Esr Spin Trapping ◽  
Spin Resonance ◽  
High Production ◽  
Resonance Spin ◽  
Spin Trapping Technique

The oxidation of azide has been studied on TiO2 powder suspensions in water, methanol, and mixtures of the two solvents. The esr spin trapping technique has been employed to provide evidence for the formation of azidyl radicals [Formula: see text]. The results show that an aqueous alkaline medium is necessary to obtain a high production of [Formula: see text] radicals. A mechanism is proposed whereby the oxidation of [Formula: see text] is mainly due to reaction with OH• radicals which are in turn generated upon capture of holes by OH− groups adsorbed on TiO2. Azidyl anions adsorb weakly on TiO2 and do not displace adsorbed OH− from the surface.

Electron spin resonance studies of the reactions of sorbate with nitrite in the presence of a spin trap

1982 ◽  
Vol 60 (12) ◽  
pp. 1598-1601 ◽  
Author(s):  
Avinash Joshi ◽  
Dennis M Hinton ◽  
George C Yang
Keyword(s):  
Electron Spin Resonance ◽  
Double Bond ◽  
Sodium Nitrite ◽  
Spin Trap ◽  
Spin Trapping ◽  
Potassium Sorbate ◽  
Radical Product ◽  
Rapid Decomposition ◽  
Esr Spectrum ◽  
Spin Resonance

An esr spectrum was generated when a spin trap, t-nitroso butane (tNB), was added to potassium sorbate solution at pH of 6.4. This spectrum can be explained by the abstraction of allylic hydrogen by NO2, generated by the decomposition of tNB, followed by spin trapping of the radical product. With increasing concentration of NO2, which was accomplished by either the addition of sodium nitrite or by lowering the pH to cause rapid decomposition of tNB, a different esr spectrum was observed. This spectrum can be accounted for by a radical formed by addition of NO2 to the 4,5 double bond of the sorbate and subsequent trapping by tNB.

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