Origin of the paramagnetic species in lignin solutions. Autoreduction of 2,6-dimethoxybenzoquinone and related quinones to radical anions in alkaline solution

1972 ◽  
Vol 37 (5) ◽  
pp. 762-767 ◽  
Author(s):  
J. D. Fitzpatrick ◽  
Cornelius. Steelink
Keyword(s):  
Alkaline Solution ◽  
Paramagnetic Species ◽  
Radical Anions

Photolytic and thermal annealing of radical anions gamma-irradiated monocarboxylic acids

1979 ◽  
Vol 44 (12) ◽  
pp. 3632-3643 ◽  
Author(s):  
Karel Mach ◽  
Igor Janovský ◽  
Karel Vacek
Keyword(s):  
Thermal Annealing ◽  
Pivalic Acid ◽  
Esr Spectra ◽  
Paramagnetic Species ◽  
Radical Anions ◽  
Γ Irradiation ◽  
Before And After ◽  
Optical Bleaching ◽  
The Difference ◽  
Gamma Irradiated

Total yields of paramagnetic species, their optical bleaching and thermal annealing in acetic, propionic, a-butyric, isobutyric, and pivalic acid γ-irradiated at 77 K were followed by ESR spectroscopy. Radical anions, always found after irradiation, disappear during optical bleaching without formation of any paramagnetic product. During thermal annealing they are converted almost quantitatively into the α-radicals of the respective acid, with the exception of pivalic acid. Amounts of radical anions were estimated from the difference of integrated ESR spectra taken before and after optical bleaching. The results show that approximately equal amounts of the reduction and oxidation paramagnetic products of the γ-irradiation can be detected.

Die Reduktion von Triphenylphosphan-Derivaten zu ihren Radikalanionen und zum Dibenzophosphol-Radikaldianion [1] / The Reduction of Triphenylphosphane Derivatives to their Radical Anions and to the Radical Dianion of Dibenzophosphole [1]

1982 ◽  
Vol 37 (11) ◽  
pp. 1382-1387 ◽  
Author(s):  
Wolfgang Kaim ◽  
Peter Hänel ◽  
Hans Bock
Keyword(s):  
Low Temperature ◽  
Alkali Metal ◽  
Ring Closure ◽  
Metal Reduction ◽  
Paramagnetic Species ◽  
Radical Anions ◽  
Spin Distribution ◽  
Pyramidal Geometry ◽  
Mercury Cathode ◽  
Electron Reduction

Triphenylphosphane 1, its oxide 2 and sulfide 3 undergo one-electron reduction at a mercury cathode in DMF to yield the corresponding radical anions. ESE analysis of the paramagnetic species is facilitated by deuteration and suggests a pyramidal geometry of the radicals. Reduction with potassium metal in DME at low temperature yields also radical anions for 2 and 3. The phosphane 1, however, reacts under phenyl cleavage and potassiumphenyl-assisted ring closure to the dianion of 5H-dibenzophosphole 4. This radical 4· ⊖⊖ is also obtainod by alkali metal reduction of P-phenyldibenzophosphole o, and its spin distribution is compared to iso-.-π-electronic radicals containing CH, N, O, S, or Se links instead of the phosphorus atom.

An Electron Spin Resonance Method for Monitoring the Progressive Replacement of Fluorine by Alkoxy Groups in Perfluorobenzophenone

1973 ◽  
Vol 51 (24) ◽  
pp. 4088-4089 ◽  
Author(s):  
Frederick Peter Sargent ◽  
Marshall Grant Bailey
Keyword(s):  
Electron Spin Resonance ◽  
Chemical Reaction ◽  
Electron Spin ◽  
Resonance Method ◽  
Paramagnetic Species ◽  
Radical Anions ◽  
Spin Resonance ◽  
Electron Spin Resonance Method ◽  
Alkoxy Groups

The use of electron spin resonance (e.s.r.) to follow the course of a chemical reaction which does not involve paramagnetic intermediates is reported. The principle of the method is the conversion of the reaction product into a paramagnetic species which may be characterized by e.s.r. In the present example, photoconversion of ketones into radical anions is used to follow the successive displacement of fluorine from perfluorobenzophenone.

Elektronentransfer und Ionenpaar-Bildung, 28. ESR/ENDOR-Untersuchungen an Radikalanionen und Kontakt-Ionenpaaren der Naturstoff-Chinone Mitomycin C, Streptonigrin, Entobex® und 10,11-Dioxobrucin/Electron Transfer and Ion Pairing, 28. ESR/ENDOR Studies of Radical Anions and Contact Ion Pairs of the Naturally Occurring Quinones Mitomycine C, Streptonigrine, Entobex® and 10,11-Dioxobrucine

1992 ◽  
Vol 47 (4) ◽  
pp. 533-546 ◽  
Author(s):  
H. Bock ◽  
P. Hänel ◽  
H.-F. Herrmann
Keyword(s):  
Electron Transfer ◽  
Mitomycin C ◽  
Ion Pairs ◽  
Radical Cations ◽  
Paramagnetic Species ◽  
Radical Anions ◽  
Multiply Charged ◽  
Naturally Occurring ◽  
Contact Ion Pairs ◽  
Triple Ion

Abstract Reduction of naturally occurring para-and ortho-benzoquinone derivatives M to their respective radical anions M·⊖ can be accomplished under largely aprotic conditions either by cautious low-temperature reaction in THF containing an excess of (2.2.2) cryptand at a potassium mirror or by using the "mild" single electron transfer reagent tetrabutylammonium boranate R4N⊕BH4⊖ in DMF. On addition of soluble alkali tetraphenylborates Me⊕[B(C6H5)4]⊖ , their hitherto unknown radical ion pairs [M·⊖ Me⊕]· and/or triple ion radical cations [Me⊕M·⊖Me⊕]·⊕ form, which might be of biological relevance in molecular carrier and "turn off -turn on" switch processes. On addition of metal perchlorates Me⊕n(ClO4⊖)n with multiply charged counter cations Me⊕n the respective paramagnetic species [M·⊖Me⊕n]·(n-1)⊕ result. Assuming exclusive one-electron transfer reductions without any redox fragmentation reac­tions, ESR, ENDOR and GENERAL TRIPLE spectra are presented and discussed for the following radical anions and radical ion pairs: mitomycin C (M·⊖ and [M·⊖Mex⊕]·(x-1)⊕ with Me⊕ = Li⊕, Na⊕), streptonigrine (M·⊖ and [M·⊖Lix⊕]·(x-1)⊕), Entobex® (M·⊖ and [M·⊖Me⊕n]·(n-1)⊕ with Me⊕n = Li⊕, Na⊕, Cd⊕⊕, (H5C6)2Tl⊕) as well as brucinequinone ([M·⊖ Me⊕n]·(n-1)⊕ with Me⊕n = Li⊕, Cd⊕⊕, Pb⊕⊕, La⊕⊕⊕).

Plasma Treatment Effect on the Paramagnetic Species of Barley Seed Radical's Intensity: An EPR study

2020 ◽  
Author(s):  
Pankaj Attri ◽  
Anan Teruki ◽  
Ryo Arita ◽  
Takamasa Okumura ◽  
Hayate Tanaka ◽  
...  
Keyword(s):  
Plasma Treatment ◽  
Treatment Effect ◽  
Barley Seed ◽  
Paramagnetic Species

The Effect of Dry Mix Sodium Hydroxide onto Workability and Compressive Strength of Geopolymer Paste

2020 ◽  
Vol 12 (9) ◽  
Author(s):  
A. Z. Mohd Ali ◽  
◽  
N. A. Jalaluddin ◽  
N. Zulkiflee ◽  
◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Alkaline Solution ◽  
High Emission ◽  
New Material ◽  
Curing Regime ◽  
Solid Form ◽  
Geopolymer Paste

The production of ordinary Portland cement (OPC) consumes considerable amount of natural resources, energy and at the same time contribute in high emission of CO2 to the atmosphere. A new material replacing cement as binder called geopolymer is alkali-activated concrete which are made from fly ash, sodium silicate and sodium hydroxide (NaOH). The alkaline solution mixed with fly ash producing alternative binder to OPC binder in concrete named geopolymer paste. In the process, NaOH was fully dissolved in water and cooled to room temperature. This study aims to eliminate this process by using NaOH in solid form together with fly ash before sodium silicate liquid and water poured into the mixture. The amount of NaOH solids were based on 10M concentration. The workability test is in accordance to ASTM C230. Fifty cubic mm of the geopolymer paste were prepared which consists of fly ash to alkaline solution ratio of 1: 0.5 and the curing regime of 80℃ for 24 hours with 100% humidity were implemented. From laboratory test, the workability of dry method geopolymer paste were decreased. The compressive strength of the dry mix of NaOH showed 55% and the workability has dropped to 58.4%, it showed strength reduction compared to the wet mix method.

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