scholarly journals Radicals formed from proton loss of carotenoid radical cations: A special form of carotenoid neutral radical occurring in photoprotection

2017 ◽  
Vol 166 ◽  
pp. 148-157 ◽  
Author(s):  
A. Ligia Focsan ◽  
Lowell D. Kispert
Keyword(s):  
Special Form ◽  
Radical Cations ◽  
Neutral Radical ◽  
Proton Loss

ESR Spectra of Para-Substituted Alkyl- and Alkenylbenzene Radical Cations in Halocarbon Matrices

1992 ◽  
Vol 47 (6) ◽  
pp. 788-796 ◽  
Author(s):  
Yoshihiro Kubozono ◽  
Masafumi Ata ◽  
Yasunobu Suzuki ◽  
Yasuhiko Gondo ◽  
Masaru Shiotani
Keyword(s):  
Radical Cation ◽  
Radical Cations ◽  
Esr Spectra ◽  
Mo Calculations ◽  
Neutral Radical ◽  
Semiempirical Mo Calculations ◽  
Γ Ray

AbstractThe ESR spectra of several para-substituted alkyl- and alkenylbenzene radical cations generated by 60Co γ-ray irradiation in halocarbon matrices at 77 K have been studied with the aid of semiempirical MO calculations. It has been found that the ethyl conformation of 1,4-diethylbenzene radical cation (1,4-DEB+. ) in CCl2FCClF2 is largely different from that in CCl3CF3. Further the ethyl and n-propyl groups in 4-ethyltoluene and 4-n-propyltoluene radical cations in CCl2FCClF2 take different conformations from that of 1,4-DEB +.. The conformations of the alkylbenzene radical cations depend strongly both on the matrices and on the substituent groups. A peculiar radiolytical reaction of 1,4-diisopropylbenzene to a deprotonation-type neutral radical in CCl2FCClF2 has been found, similarly to the case of photolysis.

Ethnic Confessional Specificity of Religiousness in Ukraine

1999 ◽  
pp. 94-105
Author(s):  
Oleksandr N. Sagan
Keyword(s):  
Ethnic Identity ◽  
Special Form

In interpreting the concept of ethnoconfessional specificity of culture, we first of all mean that this is a special form of culture of ethnically related groups of people who have their own special, religiously decorated lifestyle and ethnic identity of which is denominational oriented. This ethno-confessional community acquires, in certain socio-historical conditions, the function of a ethnic representative

Transient left ventricular dysfunction: special form of stress cardiomyopathy

2008 ◽  
Vol 149 (8) ◽  
pp. 347-352 ◽  
Author(s):  
János Tomcsányi ◽  
Miklós Somlói ◽  
Tamás Frész ◽  
Hrisula Arabadzisz ◽  
Emil Toldy-Schedel ◽  
...  
Keyword(s):  
Left Ventricular Dysfunction ◽  
Special Form ◽  
Ventricular Dysfunction ◽  
Left Ventricular ◽  
Stress Cardiomyopathy

A súlyos stressz hatására bekövetkező bal kamrai diszfunkció régóta ismert jelenség. Ennek a bal kamra apicalis dilatatiójával járó reverzíbilis formáját Sato és munkatársai 1990-ben történt első leírása nyomán „tako-tsubo”-cardiomyopathiának vagy ampulla-cardiomyopathiának hívják. Az erről szóló publikációkban mind a japán, mind az angolszász irodalomban szinte egyenlőségjelet tesznek a stressz-cardiomyopathia és a tako-tsubo-cardiomyopthia közé. Célkitűzés: A stressz indukálta reverzíbilis balkamra-diszfunkciós betegeink adatainak feldolgozásával tisztázni e kórkép lehetséges klinikai formáit és legjellemzőbb klinikai paramétereiket. Módszer: a 2002 és 2007 közötti, a Budai Irgalmasrendi Kórházban kezelt olyan betegek adatainak retrospektív feldolgozása, akiknél kimutatható volt a reverzíbilis balkamra-diszfunkció, és a koronarográfia negatív eredményt adott, valamint a klinikum és a laborparaméterek nem utaltak myocarditisre. Eredmények: Az elmúlt öt és fél évben összesen 6 olyan esetet találtunk, amelyek megfeleltek a fent leírt kritériumoknak. A betegek 55–80 év közötti nők voltak, akiknél öt esetben volt kimutatható oki tényezője a reverzíbilis balkamra-diszfunkciónak. Következtetések: A stressz indukálta cardiomyopathiának csak egyik formája a bal kamra csúcsi dilatációja, és ennek a csoportnak a fő közös jellemzője nem a tako-tsubo-szerű balkamra-tágulat, amely nincsen mindig jelen, hanem a szinte mindig meglévő QT-megnyúlás és negatív T-hullámok, amelyek a coronariabetegség nélküli akut, reverzíbilis balkamra-diszfunkciót néhány nappal követik megfigyeléseink és az irodalmi adatok alapján.

Hydrostibination of Alkynes: A Radical Mechanism

2020 ◽  
Author(s):  
Josh MacMillan ◽  
Katherine Marczenko ◽  
Erin Johnson ◽  
Saurabh Chitnis
Keyword(s):  
Density Functional ◽  
Activation Barrier ◽  
Closed Shell ◽  
Reaction Rates ◽  
Radical Mechanism ◽  
Neutral Radical ◽  
Kinetic Isotope ◽  
Rate Limiting Step ◽  
Ionic Mechanisms ◽  
Terminal Acetylenes

The addition of Sb-H bonds to alkynes was reported recently as a new hydroelementation reaction that exclusively yields anti-Markovnikov <i>Z</i>-olefins from terminal acetylenes. We examine four possible mechanisms that are consistent with the observed stereochemical and regiochemical outcomes. A comprehensive analysis of solvent, substituent, isotope, additive, and temperature effects on hydrostibination reaction rates definitively refutes three ionic mechanisms involving closed-shell charged intermediates. Instead the data support a fourth pathway featuring neutral radical Sb<sup>II</sup> and Sb<sup>III</sup> intermediates. Density Functional Theory (DFT) calculations are consistent this model, predicting an activation barrier that is within 1 kcal mol<sup>-1</sup> of the experimental value (Eyring analysis) and a rate limiting step that is congruent with experimental kinetic isotope effect. We therefore conclude that hydrostibination of arylacetylenes is initiated by the generation of stibinyl radicals, which then participate in a cycle featuring Sb<sup>II</sup> and Sb<sup>III</sup> intermediates to yield the observed <i>Z</i>-olefins as products. This mechanistic understanding will enable rational evolution of hydrostibination as a methodology for accessing challenging products such as <i>E</i>-olefins.

Reactivity Trends in the Gas Phase Addition of Acetylene to N-protonated Aryl Radical Cations

2020 ◽  
Author(s):  
Oisin Shiels ◽  
P. D. Kelly ◽  
Cameron C. Bright ◽  
Berwyck L. J. Poad ◽  
Stephen Blanksby ◽  
...  
Keyword(s):  
Gas Phase ◽  
Ion Trap ◽  
Radical Cations ◽  
Rate Coefficients ◽  
Similar Process ◽  
Ion Molecule Reactions ◽  
Aromatic Radicals ◽  
Polycyclic Aromatic ◽  
Gas Phase Ion ◽  
Type Radical

<div> <div> <div> <p>A key step in gas-phase polycyclic aromatic hydrocarbon (PAH) formation involves the addition of acetylene (or other alkyne) to σ-type aromatic radicals, with successive additions yielding more complex PAHs. A similar process can happen for N- containing aromatics. In cold diffuse environments, such as the interstellar medium, rates of radical addition may be enhanced when the σ-type radical is charged. This paper investigates the gas-phase ion-molecule reactions of acetylene with nine aromatic distonic σ-type radical cations derived from pyridinium (Pyr), anilinium (Anl) and benzonitrilium (Bzn) ions. Three isomers are studied in each case (radical sites at the ortho, meta and para positions). Using a room temperature ion trap, second-order rate coefficients, product branching ratios and reaction efficiencies are reported. </p> </div> </div> </div>

On the Reactivity of mRNA Caps: C-H Oxidative Addition of 7-Methylguanosine to Pt(0)

2019 ◽  
Author(s):  
Maria Ines Leitao ◽  
Carmen Gonzalez ◽  
Zuzanna Filipiak ◽  
Ana Petronilho
Keyword(s):  
Oxidative Addition ◽  
Carbene Complex ◽  
Proton Loss

<p>7-methylguanosine, the so-called mRNA cap 0 bears a very labile C8-H bond, due to the formation of an ylide/N-heterocyclic carbene, upon proton loss. The reaction of 7-methylguanosine with Pt(PPh3)4, via C-H oxidative addition, yields a hydrido–PtII carbene complex and this reactivity can be extrapolated to 7,9-dimethylguanine. </p>

Oxidation Ditch

2018 ◽  
Author(s):  
Gede H Cahyana
Keyword(s):  
Activated Sludge ◽  
Special Form ◽  
Oxidation Ditch ◽  
End Point ◽  
Activated Sludge System

As a part of activated sludge system, oxidation ditch has a special form like a canal without end point. Rotor is used to diffuse oxygen from air to the water.

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