scholarly journals Thermodynamic prediction of proton and hydrogen atom abstraction in dehydroascorbic acid and its bicyclic form

2021 ◽  
Vol 14 (1) ◽  
pp. 32-37
Author(s):  
Dagmar Štellerová ◽  
Vladimír Lukeš
Keyword(s):  
Vitamin C ◽  
Density Functional ◽  
Radical Scavenging ◽  
Dehydroascorbic Acid ◽  
Polarizable Continuum Model ◽  
Basis Set ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Radical Scavenging Ability ◽  
Polarizable Continuum

Abstract Conformation analysis of dehydroascorbic acid and its bicyclic form was performed using the density functional theory. For the energetically preferred conformations, ionization potentials (IP) and bond dissociation enthalpies (BDE) were calculated using the B3LYP functional and 6-311++G** basis set. The effects of aqueous solution were estimated using the solvation model based on density (SMD) and the polarizable continuum model (IEF-PCM). The obtained results were compared with available experimental data for reference L-ascorbic acid (vitamin C). Our calculations indicate that the investigated bicyclic metabolic product of vitamin C can also exhibit limited radical scavenging ability due to the thermodynamically preferred dissociation of tertiary —CH bonds.

DENSITY FUNCTIONAL THEORY STUDY ON THE MECHANISM OF TRIMETHYLAMINE-CATALYZED BAYLIS–HILLMAN REACTION

2010 ◽  
Vol 09 (supp01) ◽  
pp. 65-75 ◽  
Author(s):  
JING LI ◽  
WAN-YI JIANG
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Dft Method ◽  
Polarizable Continuum Model ◽  
Functional Theory ◽  
Reaction Barrier ◽  
Hydrogen Shift ◽  
Rate Determining Step ◽  
The Density Functional Theory ◽  
Polarizable Continuum

The trimethylamine-catalyzed Baylis–Hillman reaction of formaldehyde and vinylaldehyde has been studied with the density functional theory (DFT) method of B3LYP/6-31+G(d,p). In the gas phase, the reaction involves an amine–formaldehyde–vinylaldehyde trimolecular addition transition structure followed by rate-determining intramolecular 1,3-hydrogen shift. When a bulk solvent effect of water was considered with conductor-like polarizable continuum model (CPCM), the reaction was found to follow the sequence of Michael-addition of amine to vinylaldehyde (step 1), addition of formaldehyde (step 2), and 1,3-hydrogen shift (step 3), with the 1,3-hydrogen shift as rate-determining. The overall reaction barrier is significantly reduced. When a molecule of water is involved in the reaction, the 1,3-hydrogen shift is significantly promoted so that the rate-determining step becomes the C–C bond formation. The calculated overall reaction barrier is in agreement with experimental observations.

Predicting Notable Radical Scavenging Sites of Gnetin C Using Density Functional Theory

2019 ◽  
Vol 966 ◽  
pp. 229-233
Author(s):  
Vera Khoirunisa ◽  
Lusia Silfia Pulo Boli ◽  
Rizka Nur Fadilla ◽  
Adhitya Gandaryus Saputro ◽  
Heni Rachmawati ◽  
...  
Keyword(s):  
Density Functional ◽  
Radical Scavenging Activity ◽  
Radical Scavenging ◽  
Heterocyclic Ring ◽  
Polarizable Continuum Model ◽  
Hydroxyl Groups ◽  
Scavenging Activity ◽  
Functional Theory ◽  
Water Solvent ◽  
Polarizable Continuum

We have been investigating the scavenging activity of gnetin C theoretically in the molecular level. In this work, we perform density functional based calculations to predict the possible site of gnetin C for free radical scavenging activity. The water solvent effect is considered as polarizable continuum model. All possible scavenging sites have been evaluated by obtaining the bond dissociation enthalpy (BDE) for one hydrogen atom abstraction. The results demonstrate that O-H bonds generally have lower BDE relative to C-H bonds of gnetin C. We also find that C-H bonds in 5-membered heterocyclic ring have exceptionally lower BDE. This could be additional possible sites for gnetin C to scavenge more free radicals in addition to hydroxyl groups.

scholarly journals QUANTUM-CHEMICAL STUDY OF THE MECHANISM OF REACTION OF BENZOELACETHYLENE WITH DITIO- AND DISELENOMALONAMIDES

2020 ◽  
Vol 2020 (1) ◽  
pp. 127-135
Author(s):  
Elena Chirkina
Keyword(s):  
Quantum Chemical ◽  
Density Functional ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Polarizable Continuum Model ◽  
Basis Set ◽  
Mechanism Of Reaction ◽  
The Density Functional Theory ◽  
Two Stages ◽  
Polarizable Continuum

A mechanism of the interaction of benzoylacetylene with dithio- and diselenomalonamides has been proposed on the basis of quantum-chemical calculations in the framework of the density functional theory using the B3LYP/6-311++G(d,p) basis set taking into account solvent effects (AcOH) within the polarizable continuum model, PCM, with inclusion of the HCl molecule in the calculated space. It is shown that the reaction involves two stages to afford heterocyclic compounds of the dithiine and diselenine type

scholarly journals Synthesis, Antioxidant Activity and DFT Study of Some Novel N-Methylated Indole Incorporating Isoxazole Moieties

2019 ◽  
Vol 32 (2) ◽  
pp. 244-248
Author(s):  
J. Jani Matilda ◽  
T.F. Abbs Fen Reji
Keyword(s):  
Density Functional ◽  
Structural Parameters ◽  
Analytical Data ◽  
Radical Scavenging ◽  
Density Functional Theory Method ◽  
Basis Set ◽  
Anticancer Activities ◽  
Functional Theory ◽  
Radical Scavenging Ability ◽  
Isoxazole Derivatives

A novel series of indolyl isoxazole derivatives were synthesized and the structure of the products is confirmed on the basis of IR, 1H NMR, MS and analytical data. The synthesized compounds were evaluated for their antioxidant and anticancer activities. The results revealed clearly those compounds 4b and 4d exhibited better radical scavenging ability. The optimized structural parameters of all compounds was carried out at the B3LYP/6-311++G (d, p) level of DFT basis set implemented in Gaussian 09 program package. Theoretical calculation of the title compounds were carried out using density functional theory method (DFT).

scholarly journals Predicting the UV–vis spectra of oxazine dyes

2011 ◽  
Vol 7 ◽  
pp. 432-441 ◽  
Author(s):  
Scott Fleming ◽  
Andrew Mills ◽  
Tell Tuttle
Keyword(s):  
Excitation Energy ◽  
Density Functional ◽  
Polarizable Continuum Model ◽  
Implicit Solvent ◽  
Continuum Approach ◽  
Excitation Energies ◽  
Functional Theory ◽  
Partial Charges ◽  
Td Dft ◽  
Polarizable Continuum

In the current work we have investigated the ability of time-dependent density functional theory (TD-DFT) to predict the absorption spectra of a series of oxazine dyes and the effect of solvent on the accuracy of these predictions. Based on the results of this study, it is clear that for the series of oxazine dyes an accurate prediction of the excitation energy requires the inclusion of solvent. Implicit solvent included via a polarizable continuum approach was found to be sufficient in reproducing the excitation energies accurately in the majority of cases. Moreover, we found that the SMD solvent model, which is dependent on the full electron density of the solute without partitioning into partial charges, gave more reliable results for our systems relative to the conductor-like polarizable continuum model (CPCM), as implemented in Gaussian 09. In all cases the inclusion of solvent reduces the error in the predicted excitation energy to <0.3 eV and in the majority of cases to <0.1 eV.

scholarly journals Н-комплексы 1,2-нафтохинона с молекулами воды в водном растворе и их влияние на сдвиги полос поглощения

2021 ◽  
Vol 129 (5) ◽  
pp. 599
Author(s):  
С.Н. Цеплина ◽  
E.E. Цеплин
Keyword(s):  
Quantum Chemical ◽  
Continuum Model ◽  
Density Functional ◽  
Water Solution ◽  
Polarizable Continuum Model ◽  
Water Molecules ◽  
Absorption Bands ◽  
Functional Theory ◽  
Polarizable Continuum ◽  
Polar Water

Optical absorption spectra of 1,2-naphthoquinone in non-polar (n-hexane) and polar (water) solvents were obtained. It is shown that the use of quantum chemical calculations based on time-dependent density functional theory (TDDFT B3LYP/6-311+G(d, p)) with the polarizable continuum model (PCM) for calculating 1,2-naphthoquinone in a solution of n-hexane and hydrogen complex of 1,2-naphthoquinone with two water molecules in an aqueous medium describes well the shifts of the absorption bands of 1,2-naphthoquinone in a water solution compared to a solution in n-hexane. Based on the analysis of deviations of the calculated band shifts from the experimental ones, the question of the formation of 1,2-naphthoquinone hydrogen complexes with n water molecules (n = 1-4) in an aqueous solution is considered.

A Density Functional Theory Study of the Isomerization of Substituted 2and#39;-hydroxychalcones to the Corresponding Flavanones

2021 ◽  
Vol 43 (1) ◽  
pp. 25-25
Author(s):  
Said Abdelqadar Said Said Abdelqadar Said ◽  
Omar A Shareef and Abdulkhalik S Alkazzaz Omar A Shareef and Abdulkhalik S Alkazzaz
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Ring Closure ◽  
Basis Set ◽  
Functional Theory ◽  
Rate Determining Step ◽  
The Density Functional Theory ◽  
Electronic And Structural Properties ◽  
Maximum Hardness Principle

The transformation of 2and#39;-hydroxychalcones to their corresponding flavanones was studied theoretically by the use of the density functional theory (DFT) with B3-LYP/ 6-311G basis set to get important information about the role of both of electronic and structural properties in this process. The obtained energies were found to be in agreement with our previous results that obtained from HPLC studies. The estimated hardness, polarizability, and electrophilicity profiles were found to obey the maximum hardness principle (MHP), minimum polarizability principle (MPP), and the minimum electrophilicity principle (MEP) respectively. Flavanone ring closure was found to be the rate-determining step.

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