scholarly journals Desulfination by 2′-hydroxybiphenyl-2-sulfinate desulfinase proceeds via electrophilic aromatic substitution by the cysteine-27 proton

2017 ◽  
Vol 8 (7) ◽  
pp. 5078-5086 ◽  
Author(s):  
Inacrist Geronimo ◽  
Shawn R. Nigam ◽  
Christina M. Payne
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Electrophilic Substitution ◽  
Electrophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Functional Theory ◽  
Rate Limiting

Density functional theory shows that the rate-limiting desulfination step in biodesulfurization involves concerted electrophilic substitution with the Cys-27 proton.

Mechanism of nucleophilic substitution reactions of 4-(4ˊ-nitro)phenylnitrobenzofurazan ether with aniline in acetonitrile.

2017 ◽  
Vol 2 (10) ◽  
Author(s):  
K. Gbayo ◽  
C. Isanbor ◽  
K. Lobb ◽  
O. Oloba-Whenu
Keyword(s):  
Density Functional Theory ◽  
Nuclear Magnetic Resonance ◽  
Density Functional ◽  
Theoretical Study ◽  
Activation Parameters ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Substitution Reactions ◽  
Functional Theory ◽  
Nmr Techniques

Abstract Rate constants and activation parameters obtained for the nucleophilic aromatic substitution reactions (SNAr) of 4-substitutedphenoxy-7-nitrobenzoxadiazole (1) with aniline in acetonitrile at varying temperature using Nuclear Magnetic Resonance (NMR) techniques were reported. These results were compared with the theoretical study which identifies transformations and intermediates using Density Functional Theory (DFT).

Electrophilic aromatic substitution reactions of compounds with Craig-Möbius aromaticity

2021 ◽  
Vol 118 (39) ◽  
pp. e2102310118
Author(s):  
Yuanting Cai ◽  
Yuhui Hua ◽  
Zhengyu Lu ◽  
Qing Lan ◽  
Zuzhang Lin ◽  
...  
Keyword(s):  
Density Functional ◽  
Electronic Effect ◽  
Density Functional Theory Calculations ◽  
Electrophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Substitution Reactions ◽  
Electrophilic Attack ◽  
Functional Theory ◽  
Aromatic Species ◽  
Selective Formation

Electrophilic aromatic substitution (EAS) reactions are widely regarded as characteristic reactions of aromatic species, but no comparable reaction has been reported for molecules with Craig-Möbius aromaticity. Here, we demonstrate successful EAS reactions of Craig-Möbius aromatics, osmapentalenes, and fused osmapentalenes. The highly reactive nature of osmapentalene makes it susceptible to electrophilic attack by halogens, thus osmapentalene, osmafuran-fused osmapentalene, and osmabenzene-fused osmapentalene can undergo typical EAS reactions. In addition, the selective formation of a series of halogen substituted metalla-aromatics via EAS reactions has revealed an unprecedented approach to otherwise elusive compounds such as the unsaturated cyclic chlorirenium ions. Density functional theory calculations were conducted to study the electronic effect on the regioselectivity of the EAS reactions.

scholarly journals Utilizing the σ-complex stability for quantifying reactivity in nucleophilic substitution of aromatic fluorides

2013 ◽  
Vol 9 ◽  
pp. 791-799 ◽  
Author(s):  
Magnus Liljenberg ◽  
Tore Brinck ◽  
Tobias Rein ◽  
Mats Svensson
Keyword(s):  
Nucleophilic Substitution ◽  
Density Functional ◽  
Reaction Rates ◽  
Nucleophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Functional Theory ◽  
Aromatic Substrates ◽  
Complex Approach ◽  
Mechanistic Analysis ◽  
Rate Limiting

A computational approach using density functional theory to compute the energies of the possible σ-complex reaction intermediates, the “σ-complex approach”, has been shown to be very useful in predicting regioselectivity, in electrophilic as well as nucleophilic aromatic substitution. In this article we give a short overview of the background for these investigations and the general requirements for predictive reactivity models for the pharmaceutical industry. We also present new results regarding the reaction rates and regioselectivities in nucleophilic substitution of fluorinated aromatics. They were rationalized by investigating linear correlations between experimental rate constants (k) from the literature with a theoretical quantity, which we call the sigma stability (SS). The SS is the energy change associated with formation of the intermediate σ-complex by attachment of the nucleophile to the aromatic ring. The correlations, which include both neutral (NH3) and anionic (MeO−) nucleophiles are quite satisfactory (r = 0.93 to r = 0.99), and SS is thus useful for quantifying both global (substrate) and local (positional) reactivity in SNAr reactions of fluorinated aromatic substrates. A mechanistic analysis shows that the geometric structure of the σ-complex resembles the rate-limiting transition state and that this provides a rationale for the observed correlations between the SS and the reaction rate.

scholarly journals A Concise Synthesis of a Methyl Ester 2-Resorcinarene: A Chair-Conformation Macrocycle

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 627
Author(s):  
Michael R. Reynolds ◽  
Fraser S. Pick ◽  
John J. Hayward ◽  
John F. Trant
Keyword(s):  
Hydrogen Bond ◽  
Density Functional ◽  
Chair Conformation ◽  
Electrophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Functional Theory ◽  
Design And Synthesis ◽  
Hydrogen Bond Strength ◽  
Recognition Elements ◽  
Configurational Isomerism

Anions are important hydrogen bond acceptors in a range of biological, chemical, environmental and medical molecular recognition processes. These interactions have been exploited for the design and synthesis of ditopic resorcinarenes as the hydrogen bond strength can be tuned through the modification of the substituent at the 2-position. However, many potentially useful compounds, especially those incorporating electron-withdrawing functionalities, have not been prepared due to the challenge of their synthesis: their incorporation slows resorcinarene formation that is accessed by electrophilic aromatic substitution. As part of our broader campaign to employ resorcinarenes as selective recognition elements, we need access to these specialized materials. In this article, we report a straightforward synthetic pathway for obtaining a 2-(carboxymethyl)-resorcinarene, and resorcinarene esters in general. We discuss the unusual conformation it adopts and propose that this arises from the electron-withdrawing nature of the ester substituents that renders them better hydrogen bond acceptors than the phenols, ensuring that each of them acts as a donor only. Density Functional Theory (DFT) calculations show that this conformation arises as a consequence of the unusual configurational isomerism of this compound and interruption of the archetypal hydrogen bonding by the ester functionality.

scholarly journals Mechanism of Guaiacol Hydrodeoxygenation on Cu (111): Insights from Density Functional Theory Studies

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 523
Author(s):  
Destiny Konadu ◽  
Caroline Rosemyya Kwawu ◽  
Richard Tia ◽  
Evans Adei ◽  
Nora Henriette de Leeuw
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Reaction Path ◽  
Binding Energies ◽  
Functional Theory ◽  
Thermodynamics And Kinetics ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
The Density Functional Theory ◽  
Rate Limiting

Understanding the mechanism of the catalytic upgrade of bio-oils via the process of hydrodeoxygenation (HDO) is desirable to produce targeted oxygen-deficient bio-fuels. We have used calculations based on the density functional theory to investigate the reaction mechanism of HDO of guaiacol over Cu (111) surface in the presence of H2, leading to the formation of catechol and anisole. Our analysis of the thermodynamics and kinetics involved in the reaction process shows that catechol is produced via direct demethylation, followed by dehydrogenation of –OH and re-hydrogenation of catecholate in a concerted fashion. The de-methylation step is found to be the rate-limiting step for catechol production with a barrier of 1.97 eV. Formation of anisole will also proceed via the direct dehydroxylation of guaiacol followed by hydrogenation. Here, the rate-limiting step is the dehydroxylation step with an energy barrier of 2.07 eV. Thermodynamically, catechol formation is favored while anisole formation is not favored due to the weaker interaction seen between anisole and the Cu (111) surface, where the binding energies of guaiacol, catechol, and anisole are -1.90 eV, −2.18 eV, and −0.72 eV, respectively. The stepwise barriers also show that the Cu (111) surface favors catechol formation over anisole as the rate-limiting barrier is higher for anisole production. For catechol, the overall reaction is downhill, implying that this reaction path is thermodynamically and kinetically preferred and that anisole, if formed, will more easily transform.

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