Rhodium-Catalyzed Synthesis of Unsymmetric Di(heteroaryl)ureas Involving an Equilibrium Shift

2021 ◽  
Author(s):  
Mieko Arisawa ◽  
Taro Mizuno ◽  
Kanako Nozawa-Kumada ◽  
Kaori Itto-Nakama ◽  
Miyu Furuta ◽  
...  
Keyword(s):  
Equilibrium Shift

Equilibrium shift by target DNA substrates for determination of DNA binding ligands

2007 ◽  
Vol 17 (1) ◽  
pp. 68-72 ◽  
Author(s):  
Saori Tsujita ◽  
Mikimasa Tanada ◽  
Tomonobu Kataoka ◽  
Shigeki Sasaki
Keyword(s):  
Dna Binding ◽  
Target Dna ◽  
Equilibrium Shift ◽  
Dna Substrates

scholarly journals Electrochemical and Molecular Assessment of Quinones as CO2-Binding Redox Molecules for Carbon Capture

2021 ◽  
Author(s):  
Fritz Simeon ◽  
Michael C. Stern ◽  
Kyle M. Diederichsen ◽  
Yayuan Liu ◽  
Howard J. Herzog ◽  
...  
Keyword(s):  
Carbon Capture ◽  
Peak Height ◽  
Peak Position ◽  
Sweep Rate ◽  
Practical Implementation ◽  
Reduction Wave ◽  
Electrochemical Cycling ◽  
Equilibrium Shift ◽  
Lower Vapor Pressure ◽  
Redox Molecules

The complexation and decomplexation of CO2 with a series of quinones of different basicity during electrochemical cycling in dimethylformamide solutions were studied systematically by cyclic voltammetry. In the absence of CO2, all quinones exhibited two well-separated reduction waves. For weakly complexing quinones, a positive shift in the second reduction wave was observed in the presence of CO2, corresponding to the dianion quinone-CO2 complex formation. The peak position and peak height of the first re-duction wave were unchanged, indicating no formation of complexes between the semiquinones and CO2. The relative heights of both reduction waves remained constant. In the case of strongly complexing quinones, the second reduction wave disappeared while the peak height of the first reduction wave approximately doubled, indicating that the two electrons transferred simultaneously at this potential. The observed voltammograms were rationalized through several equilibrium arguments. Both weakly and strongly complexing quinones underwent either stepwise or concerted mechanisms of oxidation and CO2 dissociation depending on the sweep rate in the cyclic voltammetric experiments. Relative to stepwise oxidation, the concerted process requires a more positive electrode potential to remove the electron from the carbonate complexes to release CO2 and regenerate the quinone. For weakly complexing quinones, the stepwise process corresponds to oxidation of the uncomplexed dianion and accompanying equilibrium shift, while for strongly complexing quinones the stepwise process would correspond to the oxidation of mono(carbonate) dianion to the complexed semiquinone and accompanying equilibrium shift. This study provides a mechanistic interpretation of the interactions that lead to the formation of quinone-CO2 complexes required for the potential development of an energy efficient electrochemical separation process and discusses important considerations for practical implementation of CO2 capture in the presence of oxygen with lower vapor pressure solvents.

Prototropic Tautomerism and Some Features of the IR Spectra of 2-(3-Chromenyl)-1-hydroxyimidazoles

2019 ◽  
Vol 72 (9) ◽  
pp. 699 ◽  
Author(s):  
Polina A. Nikitina ◽  
Tatiana Yu. Koldaeva ◽  
Vitaly S. Mityanov ◽  
Vladimir S. Miroshnikov ◽  
Elizaveta I. Basanova ◽  
...  
Keyword(s):  
Solid State ◽  
Ir Spectra ◽  
Carbonyl Group ◽  
Tautomeric Form ◽  
Imidazole Ring ◽  
General Effect ◽  
Dmso Solution ◽  
Prototropic Tautomerism ◽  
Leading Role ◽  
Equilibrium Shift

Prototropic tautomerism of 2-(3-chromenyl)-1-hydroxyimidazoles with various substituents in the chromenyl moiety (1-hydroxyimidazole – imidazole N-oxide) was studied by means of 1H NMR and IR spectroscopies. It was demonstrated that in d6-DMSO solution, the substituents in the chromenyl ring have no influence on the equilibrium shift: the prevalence of the N-oxide tautomeric form is caused by the possibility of stabilization of the planar structure with the help of the carbonyl group in position 5 of the imidazole ring. In contrast, in the solid state the general effect of the chromenyl substituent in position 2 of imidazole plays the leading role. The increase in general electron-withdrawing effect of the chromenyl moiety leads to the prevalence of the imidazole N-oxide tautomer.

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