Effect of steric hindrance on hydrogen-bonding interaction between polyesters and natural polyphenol catechin

2004 ◽  
Vol 91 (6) ◽  
pp. 3565-3573 ◽  
Author(s):  
Bo Zhu ◽  
Jianchun Li ◽  
Yong He ◽  
Hideki Yamane ◽  
Yoshiharu Kimura ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Steric Hindrance ◽  
Hydrogen Bonding Interaction ◽  
Bonding Interaction ◽  
Natural Polyphenol

scholarly journals Kinetics of Free Radical Polymerization of N-Substituted Amides and Their Structural Implications

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Anca Aldea ◽  
Ana-Maria Albu ◽  
Alina Nicolescu ◽  
Victorita Tecuceanu
Keyword(s):  
Hydrogen Bonding ◽  
Free Radical ◽  
Nitrogen Atom ◽  
Steric Hindrance ◽  
Solvent Polarity ◽  
Hydrogen Bonding Interaction ◽  
H Nmr ◽  
Bonding Interaction ◽  
Kinetics Of ◽  
C Nmr

Two N-substituted amides (N-acryloyl morpholine and N-methyl-N-vinylacetamide) were polymerized in different solvents using radical initiator. The tacticity of obtained polymers was determined by 400 MHz1H-NMR and13C-NMR. At a given temperature, the syndiotacticity increased with increasing the solvent polarity. This solvent effect may be related to the hydrogen bonding interaction among solvent, monomer, and/or growing species. A peculiar aspect regards the steric hindrance at the nitrogen atom.

Hydrogen-bonding interaction of methyl-substituted pyridines with thioacetamide: steric hindrance of methyl group

2001 ◽  
Vol 345 (3-4) ◽  
pp. 338-344 ◽  
Author(s):  
Kee-Hyun Choi ◽  
Ho-Jin Lee ◽  
Alfred Karpfen ◽  
Chang-Ju Yoon ◽  
Jeunghee Park ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Steric Hindrance ◽  
Hydrogen Bonding Interaction ◽  
Methyl Group ◽  
Bonding Interaction ◽  
Substituted Pyridines

Radical Enzymes Control the Chemistry of Their Highly Reactive Intermediates Using the Quantum Coulombic Effect

2020 ◽  
Author(s):  
Hossein Khalilian ◽  
Gino A. DiLabio
Keyword(s):  
Hydrogen Bonding ◽  
Molecular Orbital ◽  
Reactive Intermediates ◽  
Hydrogen Bonding Interaction ◽  
Orbital Ordering ◽  
Dynamic Nature ◽  
Radical Intermediate ◽  
Highest Occupied Molecular Orbital ◽  
Bonding Interaction ◽  
Close Proximity

Here, we report an exquisite strategy that the B12 enzymes exploit to manipulate the reactivity of their radical intermediate (Adenosyl radical). Based on the quantum-mechanic calculations, these enzymes utilize a little known long-ranged through space quantum Coulombic effect (QCE). The QCE causes the radical to acquire an electronic structure that contradicts the Aufbau Principle: The singly-occupied molecular orbital (SOMO) is no longer the highest-occupied molecular orbital (HOMO) and the radical is unable to react with neighbouring substrates. The dynamic nature of the enzyme and its structure is expected to be such that the reactivity of the radical is not restored until it is moved into close proximity of the target substrate. We found that the hydrogen bonding interaction between the nearby conserved glutamate residue and the ribose ring of Adenosyl radical plays a crucial role in manipulating the orbital ordering

Radical Enzymes Control the Chemistry of Their Highly Reactive Intermediates Using the Quantum Coulombic Effect

2020 ◽  
Author(s):  
Hossein Khalilian ◽  
Gino A. DiLabio
Keyword(s):  
Hydrogen Bonding ◽  
Molecular Orbital ◽  
Reactive Intermediates ◽  
Hydrogen Bonding Interaction ◽  
Orbital Ordering ◽  
Dynamic Nature ◽  
Radical Intermediate ◽  
Highest Occupied Molecular Orbital ◽  
Bonding Interaction ◽  
Close Proximity

Here, we report an exquisite strategy that the B12 enzymes exploit to manipulate the reactivity of their radical intermediate (Adenosyl radical). Based on the quantum-mechanic calculations, these enzymes utilize a little known long-ranged through space quantum Coulombic effect (QCE). The QCE causes the radical to acquire an electronic structure that contradicts the Aufbau Principle: The singly-occupied molecular orbital (SOMO) is no longer the highest-occupied molecular orbital (HOMO) and the radical is unable to react with neighbouring substrates. The dynamic nature of the enzyme and its structure is expected to be such that the reactivity of the radical is not restored until it is moved into close proximity of the target substrate. We found that the hydrogen bonding interaction between the nearby conserved glutamate residue and the ribose ring of Adenosyl radical plays a crucial role in manipulating the orbital ordering

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