scholarly journals Cephalexin Degradation Initiated by OH Radicals: Theoretical Prediction of the Mechanisms and the Toxicity of Byproducts

2021 ◽  
Author(s):  
R. Masmoudi ◽  
S. Khettaf ◽  
A. Soltani ◽  
A. Dibi ◽  
L. Messaadia ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Theoretical Prediction ◽  
Hydroxyl Radical ◽  
Density Functional ◽  
Aquatic Organisms ◽  
Addition Reactions ◽  
Oh Radicals ◽  
Functional Theory ◽  
Radical Attack ◽  
Mechanism Of The Reaction

Abstract In this work, density functional theory is used to study the local reactivity of cephalexin (CLX) to radical attack and explain the mechanism of the reaction between CLX and hydroxyl radical attack leading to degradation byproducts. The reaction between •OH and CLX is supposed to lead to either an addition of a hydroxyl radical or an abstraction of a hydrogen. The results showed that the affinity of cephalexin for addition reactions increases as it passes from the gas to the aqueous phase and decreases as it passes from the neutral to the ionized form. Thermodynamic data confirmed that OH addition radicals (Radd) are thermodynamically favored over H abstraction radicals (Rabs). The ecotoxicity assessments of CLX and its byproducts are estimated from the acute toxicities toward green algae, Daphnia and fish. The formation of byproducts is safe for aquatic organisms, and only one byproduct is harmful to Daphnia.

Synthesis of novel N-functionalized 4-aryl-tetrahydrobiquinoline-2,5-(1H,3H)-diones via one-pot three-component reaction: a joint experimental and computational study

2018 ◽  
Vol 96 (12) ◽  
pp. 1071-1078
Author(s):  
Vahideh Zadsirjan ◽  
Sayyed Jalil Mahdizadeh ◽  
Majid M. Heravi ◽  
Masumeh Heydari
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Computational Study ◽  
Reaction Pathway ◽  
Deep Insight ◽  
One Pot ◽  
Functional Theory ◽  
Three Component Reaction ◽  
High Yields ◽  
Mechanism Of The Reaction

A novel series of N-functionalized 4-aryl-tetrahydrobiquinoline-2,5-(1H,3H)-diones were synthesized in high yields by a one-pot three-component reaction involving 2-chloroquinoline-3-carbaldehydes, Meldrum’s acid, and enaminones (dimedone-based enaminones) in the presence of K2CO3 in CH3CN under reflux condition. To gain a deep insight on the mechanism of the reaction, an extensive series of quantum mechanics calculations in the framework of density functional theory (DFT) were carried out for supporting the suggested reaction pathway.

scholarly journals Role of hemibonding in the structure and ultraviolet spectroscopy of the aqueous hydroxyl radical

2020 ◽  
Vol 22 (47) ◽  
pp. 27829-27844
Author(s):  
Bhaskar Rana ◽  
John M. Herbert
Keyword(s):  
Density Functional Theory ◽  
Hydroxyl Radical ◽  
Density Functional ◽  
Ultraviolet Spectroscopy ◽  
Functional Theory ◽  
Solvation Structure

The presence of a two-center, three-electron hemibond in the solvation structure of the aqueous hydroxl radical has long been debated, as its appearance can be sensitive to self-interaction error in density functional theory.

DIRECT DENSITY FUNCTIONAL THEORY DYNAMICS STUDY FOR THE CH3OCF2CF2OCH3 + OH REACTION

2011 ◽  
Vol 10 (02) ◽  
pp. 231-244 ◽  
Author(s):  
HONG-BO YU ◽  
FENG-CHAO CUI ◽  
YONG-XIA WANG ◽  
HONG-XIA LIU ◽  
JING-YAO LIU
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Theoretical Data ◽  
State Theory ◽  
Stationary Points ◽  
Enthalpies Of Formation ◽  
Oh Radicals ◽  
Isodesmic Reactions ◽  
Functional Theory ◽  
Barrier Heights

The mechanism and kinetics of the reaction of CH3OCF2CF2OCH3 with OH radicals have been studied theoretically by a direct density functional theory dynamics method. All possible H -abstraction channels and displacement processes taking place on two different conformers of CH3OCF2CF2OCH3 have been taken into consideration. The potential energy surface information including the optimized geometries and harmonic vibrational frequencies of all the stationary points and barrier heights involved in these channels were obtained at the BB1K/6-31+G(d,p) level of theory. The rate constants were calculated using improved canonical variational transition state theory (ICVT) with the small-curvature tunneling correction (SCT) over the temperature range of 200–2000 K. The overall rate constant for the title reaction, which was obtained by considering the weight factor of each conformer from the Boltzman distribution function, is in reasonable agreement with the available experimental value. Three-term Arrhenius expression is fitted to be k T = 1.56 × 10-20 T 2.47 exp (-124.64/ T ) cm 3 molecule-1 s-1 (200–2000 K). Also, the enthalpies of formation of the reactant CH3OCF2CF2OCH3 and product radicals CH3OCF2CF2OCH2 and CH3OCF2CF2O , which lack experimental or theoretical data, were evaluated via applying isodesmic reactions.

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