THE INHIBITED AUTOXIDATION OF STYREN: PART IV. SOLVENT EFFECTS

1964 ◽  
Vol 42 (5) ◽  
pp. 1044-1056 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Hydrogen Bonding ◽  
Transition State ◽  
Solvent Effects ◽  
Dielectric Constants ◽  
Hydroxyl Group ◽  
Phenolic Antioxidants ◽  
Oxidation Reactions ◽  
Effect Of Solvents ◽  
Hydrogen Bonding Interactions ◽  
Influence Of Solvents

The influence of solvents on the rate of the uninhibited oxidation of styrene can be roughly correlated with the dielectric constants of the solvents. It is suggested that the propagation reaction involves a dipolar transition state and that the magnitude of the solvent effects might be used to identify dipolar transition states in other oxidation reactions. The effect of solvents on the rate of oxidation of styrene inhibited by phenolic antioxidants is attributed to hydrogen bonding interactions between the phenolic hydroxyl group and the solvent. The magnitude of these interactions depends on the acidity of the phenol and on the degree of steric protection afforded the hydroxyl group by ortho-alkyl substituents.

scholarly journals A crystallographic study of the Toho-1 β-lactamase acylation mechanism

2014 ◽  
Vol 70 (a1) ◽  
pp. C1207-C1207
Author(s):  
Leighton Coates
Keyword(s):  
Hydrogen Bonding ◽  
Transition State ◽  
Active Site ◽  
Catalytic Mechanism ◽  
Substrate Binding ◽  
Ligand Complex ◽  
Transition State Analog ◽  
Hydrogen Bonding Interactions ◽  
Active Site Region ◽  
Neutron Crystallography

β-lactam antibiotics have been used effectively over several decades against many types of highly virulent bacteria. The predominant cause of resistance to these antibiotics in Gram-negative bacterial pathogens is the production of serine β-lactamase enzymes. A key aspect of the class A serine β-lactamase mechanism that remains unresolved and controversial is the identity of the residue acting as the catalytic base during the acylation reaction. Multiple mechanisms have been proposed for the formation of the acyl-enzyme intermediate that are predicated on understanding the protonation states and hydrogen-bonding interactions among the important residues involved in substrate binding and catalysis of these enzymes. For resolving a controversy of this nature surrounding the catalytic mechanism, neutron crystallography is a powerful complement to X-ray crystallography that can explicitly determine the location of deuterium atoms in proteins, thereby directly revealing the hydrogen-bonding interactions of important amino acid residues. Neutron crystallography was used to unambiguously reveal the ground-state active site protonation states and the resulting hydrogen-bonding network in two ligand-free Toho-1 β-lactamase mutants which provided remarkably clear pictures of the active site region prior to substrate binding and subsequent acylation [1,2] and an acylation transition-state analog, benzothiophene-2-boronic acid (BZB), which was also isotopically enriched with 11B. The neutron structure revealed the locations of all deuterium atoms in the active site region and clearly indicated that Glu166 is protonated in the BZB transition-state analog complex. As a result, the complete hydrogen-bonding pathway throughout the active site region could then deduced for this protein-ligand complex that mimics the acylation tetrahedral intermediate [3].

scholarly journals Photoluminescence of self-assembled Ag(i) and Au(i) N-heterocyclic carbene complexes. Interplay the aurophilic, hydrogen bonding and hydrophobic interactions

RSC Advances ◽  
2017 ◽  
Vol 7 (24) ◽  
pp. 14611-14617 ◽  
Author(s):  
Herbert J. H. Syu ◽  
Josh Y. Z. Chiou ◽  
Ju-Chun Wang ◽  
Ivan J. B. Lin
Keyword(s):  
Hydrogen Bonding ◽  
Liquid Crystal ◽  
Phase Formation ◽  
Alkyl Chain ◽  
Hydrophobic Interactions ◽  
Hydroxyl Group ◽  
Liquid Crystal Phase ◽  
Carbene Complexes ◽  
Hydrogen Bonding Interactions ◽  
Long Alkyl Chain

The incorporation of a 2-hydroxyl group at the long alkyl chain of NHC increases the hydrogen bonding interactions and thus induces the liquid crystal phase formation for the tetra nuclear Ag–NHC complex.

Aziridine Scaffolds for the Detection and Quantification of Hydrogen-Bonding Interactions through Transition-State Stabilization

2010 ◽  
Vol 123 (3) ◽  
pp. 767-770
Author(s):  
Luciana Giordano ◽  
Cam T. Hoang ◽  
Michael Shipman ◽  
James H. R. Tucker ◽  
Tiffany R. Walsh
Keyword(s):  
Hydrogen Bonding ◽  
Transition State ◽  
Hydrogen Bonding Interactions ◽  
Transition State Stabilization ◽  
Detection And Quantification

scholarly journals Bis(μ2-benzoato-κ2 O,O′)bis(benzoato-κO)bis(ethanol-κO)bis(μ3-hydroxido)hexakis(μ-pyrazolato-κ2 N,N′)hexacopper(II) ethanol disolvate

IUCrData ◽  
2019 ◽  
Vol 4 (9) ◽  
Author(s):  
Marisol Ledezma-Gairaud ◽  
Leslie W. Pineda
Keyword(s):  
Hydrogen Bonding ◽  
Solvent Molecule ◽  
The Other ◽  
Hydroxyl Group ◽  
Asymmetric Unit ◽  
Coordination Environment ◽  
Hydrogen Bonding Interactions ◽  
Carboxylate Groups ◽  
Square Planar ◽  
Supramolecular Arrangements

Trinuclear copper–pyrazolate entities are present in various Cu-based enzymes and nanojar supramolecular arrangements. The reaction of copper(II) chloride with pyrazole (pzH) and sodium benzoate (benzNa) assisted by microwave radiation afforded a neutral centrosymmetric hexanuclear copper(II) complex, [Cu6(C7H5O2)4(OH)2(C3H3N2)6(C2H5OH)2]·2C2H5OH. Half a molecule is present in the asymmetric unit that comprises a [Cu3(μ3-OH)(pz)3]2+ core with the copper(II) atoms arranged in an irregular triangle. The three copper(II) atoms are bridged by an O atom of the central hydroxyl group and by three bridging pyrazolate ligands on each of the sides. The carboxylate groups show a chelating mode to one and a bridging syn,syn mode to the other two CuII atoms. The coordination environment of one CuII atom is square-planar while it is distorted square-pyramidal for the other two. Two ethanol molecules are present in the asymmetric unit, one binding to one of the CuII atoms, one as a solvent molecule. In the crystal, stabilization arises from intermolecular O—H...O hydrogen-bonding interactions.

Are solvent effects important for intramolecular C—H···O − hydrogen bonding interactions?

2018 ◽  
Vol 32 (4) ◽  
pp. e3912
Author(s):  
Jinhu Wang ◽  
Linjun Shao ◽  
Peng Yan ◽  
Chunli Liu ◽  
Xuejing Liu ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Solvent Effects ◽  
Hydrogen Bonding Interactions
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