Use of a stable free radical as a NMR spin probe for studying intermolecular interactions. XIV. A proton relaxation study of the hydrogen bond involving a stable free radical

1977 ◽  
Vol 67 (10) ◽  
pp. 4760-4767 ◽  
Author(s):  
Kazunaka Endo ◽  
Isao Morishima ◽  
Teijiro Yonezawa
Keyword(s):  
Hydrogen Bond ◽  
Free Radical ◽  
Intermolecular Interactions ◽  
Spin Probe ◽  
Proton Relaxation ◽  
Stable Free Radical ◽  
Relaxation Study

scholarly journals Pyridylketenes. Structure reactivity effects in nucleophilic and radical addition

2004 ◽  
Vol 76 (11) ◽  
pp. 1953-1966 ◽  
Author(s):  
A. D. Allen ◽  
A. V. Fedorov ◽  
K. Najafian ◽  
T. T. Tidwell ◽  
S. Vukovic
Keyword(s):  
Hydrogen Bond ◽  
Free Radical ◽  
Intramolecular Hydrogen Bond ◽  
Rate Constant ◽  
Radical Addition ◽  
Stable Free Radical ◽  
Intramolecular Hydrogen

2-, 3-, and 4-Pyridylketenes have been generated in CH3CN by photochemical Wolff rearrangements and identified by their ketenyl absorption in the infrared at 2127, 2125, and 2128 cm–1, respectively. Reaction of these pyridylketenes with n-BuNH2 results in the formation of intermediate amide enols from the 3- and 4-pyridylketenes, which are then converted to the corresponding pyridylacetamides. However , 2-pyridylketene forms a long-lived 1,2-dihydropyridine intermediate stabilized by an intramolecular hydrogen bond, and this is converted to the 2-pyridylacetamide with a rate constant 107 less than those for the conversion of the amide enols from the 3- and 4-pyridylketenes to amides. Hydration of the pyridylketenes results in the formation of an acid enol intermediate in the case of the 3-isomer, while the 2- and 4-isomers form longer-lived dihydropyridines. The pyridylketenes react with the stable free radical tetramethylpiperidinyloxyl (TEMPO,TO) forming 1,2-diaddition products ArCH(OT)CO2T.

Esr Indication of Heavy Metal Contamination of Urban Atmosphere

1993 ◽  
Vol 27 (7-8) ◽  
pp. 263-269 ◽  
Author(s):  
B. Iosefzon-Kuyavskaya ◽  
N. Myrlyan ◽  
A. Shames
Keyword(s):  
Heavy Metal ◽  
Air Pollution ◽  
Electron Spin Resonance ◽  
Free Radical ◽  
Metal Contamination ◽  
Heavy Metal Contamination ◽  
Urban Atmosphere ◽  
Stable Free Radical ◽  
Spin Resonance ◽  
Line Characteristic

Electron Spin Resonance (ESR) was used for the examination oi dust samples collected from snow in an urban area. On the main doublet ESR line attributed to the signal of paramagnetic metals, a singlet line characteristic for stable free radical centers (FRC) was observed. A negative correlation of significant level between FRC signal intensity and heavy metal (HM) content was established. It was shown that FRC line intensity of dust may be used as a surrogate parameter for the estimation of air pollution by HM.

scholarly journals Microwave-Assisted Synthesis, Characterization, Antimicrobial and Antioxidant Activity of Some New Isatin Derivatives

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
G. Kiran ◽  
T. Maneshwar ◽  
Y. Rajeshwar ◽  
M. Sarangapani
Keyword(s):  
Antioxidant Activity ◽  
Free Radical ◽  
Radical Scavenging ◽  
Microwave Assisted Synthesis ◽  
Stable Free Radical ◽  
Ft Ir ◽  
Antimicrobial And Antioxidant Activity ◽  
New Compounds ◽  
Isatin Derivatives

A series of β-Isatin aldehyde-N,N′-thiocarbohydrazone derivatives were synthesized and assayed for theirin vitroantimicrobial and antioxidant activity. The new compounds were characterized based on spectral (FT-IR, NMR, MS) analyses. All the test compounds possessed a broad spectrum of activity having MIC values rangeing from 12.5 to 400 μg/ml against the tested microorganisms. Among the compounds3e,3jand3nshow highest significant antimicrobial activity. The free radical scavenging effects of the test compounds against stable free radical DPPH (α,α-diphenyl-β-picryl hydrazyl) and H2O2were measured spectrophotometrically. Compounds3j,3n,3l, and3e, respectively, had the most effective antioxidant activity against DPPH and H2O2scavenging activity.

2,4-Diamino-6-phenyl-1,3,5-triazin-1-ium nitrate: intriguing crystal structure with high Z′/Z′′ and hydrogen bond numbers and Hirshfeld surface analysis of intermolecular interactions

CrystEngComm ◽  
2021 ◽  
Author(s):  
Nicoleta Caimac ◽  
Elena Melnic ◽  
Diana Chisca ◽  
Marina S. Fonari
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Surface Analysis ◽  
Intermolecular Interactions ◽  
Title Compound ◽  
Ionic Species ◽  
Hirshfeld Surface ◽  
Hirshfeld Surface Analysis ◽  
Asymmetric Unit ◽  
Space Group

The title compound crystallises in the triclinic centrosymmetric space group P1̄ with an intriguing high number of crystallographically unique binary salt-like adducts (Z′ = 8) and a total number of ionic species (Z′′ = 16) in the asymmetric unit.

Rational Functionalization Towards Green Materials: Novel Redox Active TEMPO Stable Free Radical‐Hydrochar Composites

ChemSusChem ◽  
2021 ◽  
Author(s):  
Petre Ionita ◽  
Greta Patrinoiu ◽  
Jose M. Calderon Moreno ◽  
Simona Somacescu ◽  
Adina M. Musuc ◽  
...  
Keyword(s):  
Free Radical ◽  
Stable Free Radical ◽  
Green Materials ◽  
Redox Active

Synthesis and Characterization of Some Novel Homo- and Hetero-Diradicals of Hydrazyl and Nitroxide Type

2007 ◽  
Vol 60 (3) ◽  
pp. 173 ◽  
Author(s):  
Petre Ionita ◽  
Floriana Tuna ◽  
Marius Andruh ◽  
Titus Constantinescu ◽  
Alexandru T. Balaban
Keyword(s):  
Free Radical ◽  
Potassium Permanganate ◽  
Lead Dioxide ◽  
Magnetic Behaviour ◽  
Synthesis And Characterization ◽  
Stable Free Radical ◽  
Ms Analysis ◽  
New Compounds

Starting from the well known stable free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH; 2a) and its congener 2,2-diphenyl-1-(4-cyano-2,6-dinitrophenyl)hydrazyl 2b, or from their reduced hydrazine counterparts 1a,b, it was possible to obtain the p-quinonoid compounds 4a,b by oxidation with ceric (Ce4+) sulfate, which by reduction gave the corresponding hydroxyl derivatives 2-phenyl-2-(4-hydroxyphenyl)-1-picrylhydrazine 5a or 2-phenyl-2-(4-hydroxyphenyl)-1-(4-cyano-2,6-dinitrophenyl)hydrazine 5b. These hydroxyl derivatives (5a,b) react with 4-carboxy-TEMPO or 2,2-diphenyl-1-(4-carboxy-2,6-dinitrophenyl)hydrazine to form the corresponding esters 6a,b or 8a,b. These esters (6a,b and 8a,b) lead to the hybrid hetero diradicals (nitroxide–hydrazyl type) 7a,b or homo biradicals (hydrazyl–hydrazyl type) 9a,b by oxidation with lead dioxide or potassium permanganate. The new compounds were characterized by UV-vis, NMR, EPR, and MS analysis, and their magnetic behaviour was investigated.

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