THEORETICAL STUDY OF THE SUBSTITUENT EFFECTS ON THE REACTION ENTHALPIES OF THE ANTIOXIDANT MECHANISMS OF STOBADINE DERIVATIVES IN THE GAS-PHASE AND WATER

2013 ◽  
Vol 12 (02) ◽  
pp. 1250116 ◽  
Author(s):  
MEYSAM NAJAFI ◽  
MOHAMMAD NAJAFI ◽  
HOUSHANG NAJAFI
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Substituent Effects ◽  
Partial Charge ◽  
Action Mechanisms ◽  
Dissociation Enthalpy ◽  
Proton Dissociation ◽  
Highest Occupied Molecular Orbital ◽  
Phase Water ◽  
Antioxidant Mechanisms

In this paper the reaction enthalpies of three antioxidant action mechanisms, HAT, SET–PT, and SPLET, for mono-substituted Stobadines were calculated in gas-phase and water. Results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP), and electron transfer enthalpy (ETE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In comparison to gas-phase, water attenuates the substituent effect on all reaction enthalpies. Results show that IP and BDE values can be successfully correlated with the indolic N–H bond length after electron abstraction, R(N–H+•), and the partial charge on the indolyl radical nitrogen atom, q( N ). Furthermore, calculated IP and PA values for mono-substituted Stobadines show linear dependence on the energy of the highest occupied molecular orbital (E HOMO ) of studied molecules in the two environments. SPLET represents the thermodynamically preferred mechanism in water.

DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Sesamol Derivatives in the Gas phase and water

2012 ◽  
Vol 90 (10) ◽  
pp. 915-926 ◽  
Author(s):  
Meysam Najafi ◽  
Mohammad Najafi ◽  
Houshang Najafi
Keyword(s):  
Gas Phase ◽  
Substituent Effects ◽  
Ortho Position ◽  
Meta Position ◽  
Action Mechanisms ◽  
Dissociation Enthalpy ◽  
Highest Occupied Molecular Orbital ◽  
B3lyp Method ◽  
Phase Water ◽  
Antioxidant Mechanisms

In this paper, the study of various ortho and meta–substituted Sesamol derivatives is presented. The reaction enthalpies related to three antioxidant action mechanisms HAT, SET–PT, and SPLET for substituted Sesamols, have been calculated using the DFT/B3LYP method in gas phase and water. Calculated results show that electron-withdrawing substituents increase the bond dissociation enthalpy (BDE), ionization potential (IP), and electron transfer enthalpy (ETE), while electron-donating ones cause a rise in the proton dissociation enthalpy (PDE) and proton affinity (PA). In the ortho position, substituents show a larger effect on reaction enthalpies than in the meta position. In comparison with the gas phase, water attenuates the substituent effect on all reaction enthalpies. In the gas phase, BDEs are lower than PAs and IPs, i.e., HAT represents the thermodynamically preferred pathway. On the other hand, the SPLET mechanism represents the thermodynamically favored process in water. Results show that calculated enthalpies can be successfully correlated with Hammett constants (σm) of the substituted Sesamols. Furthermore, calculated IP and PA values for substituted Sesamols show linear dependence on the energy of the highest occupied molecular orbital (EHOMO).

Theoretical study of substituent effects on the gas-phase stabilities of phenoxide anions

2012 ◽  
Vol 26 (2) ◽  
pp. 115-123 ◽  
Author(s):  
Kazuhide Nakata ◽  
Mizue Fujio ◽  
Kichisuke Nishimoto ◽  
Yuho Tsuno
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Substituent Effects

scholarly journals Theoretical Study about the Effect of Halogen Substitution on the Reactivity of Antitumor 3-Formylchromones and Their Free Radicals

2017 ◽  
Vol 2017 ◽  
pp. 1-5
Author(s):  
Maximiliano Martínez-Cifuentes ◽  
Boris Weiss-López ◽  
Ramiro Araya-Maturana
Keyword(s):  
Free Radicals ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Theoretical Study ◽  
Computational Study ◽  
Bond Dissociation Enthalpy ◽  
Radical Species ◽  
Anticancer Compounds ◽  
Dissociation Enthalpy ◽  
Polarizable Continuum

The mandatory presence of a chlorine atom on the aromatic ring of 6-hydroxy-3-formyl angular chromones, on the respiration inhibition of mammary carcinoma mouse, is explained through a computational study of these compounds. This study analyzes the reactivity of the neutral molecules and their free radicals, in gas phase and with water solvation, incorporated by the polarizable continuum medium (PCM) approach. Electrophilic reactivities were evaluated using Fukui (f+) and Parr (P+) functions. The stabilities of radical species formed by the abstraction of a hydrogen atom from the O-H bond were evaluated by bond dissociation enthalpy (BDE) and spin density (SD) calculations. This study has potential implications for the design of chromone analogues as anticancer compounds.

scholarly journals Gallic acid: thermodynamics of the homolytic and heterolytic phenolic O—H bonds splitting-off

2016 ◽  
Vol 9 (2) ◽  
pp. 114-123
Author(s):  
Peter Škorňa ◽  
Martin Michalík ◽  
Erik Klein
Keyword(s):  
Gallic Acid ◽  
Gas Phase ◽  
Bond Dissociation Enthalpy ◽  
Carboxylic Group ◽  
Proton Affinities ◽  
Dissociation Enthalpy ◽  
Proton Dissociation ◽  
Pcm Model ◽  
Antioxidant Potency ◽  
Primary Antioxidant

Abstract The DFT study of primary antioxidant action of gallic acid and its carboxylic anion is presented in the gas-phase, benzene and water. Corresponding reaction enthalpies for three possible mechanisms was calculated using B3LYP/6-311++G** method. Bond dissociation enthalpy (BDE) and proton dissociation enthalpy (PDE) of 4-OH group was found to be the lowest in gas-phase as well as in both solvents approximated by IEF-PCM model. Ionization potentials (IPs) were higher than BDEs in all cases. Deprotonation of carboxylic group result in increased antioxidant potency as drop in BDE, proton affinities (PAs) and IPs was indicated in all environments.

Theoretical Study of Substituent Effects on the Gas-Phase Acidities of Benzoic and Phenylacetic Acids

ChemPlusChem ◽  
2013 ◽  
Vol 78 (9) ◽  
pp. 1099-1108 ◽  
Author(s):  
Kazuhide Nakata ◽  
Mizue Fujio ◽  
Kichisuke Nishimoto ◽  
Yuho Tsuno
Keyword(s):  
Gas Phase ◽  
Theoretical Study ◽  
Substituent Effects

scholarly journals THERMOCHEMICAL PARAMETERS OF ERGOTHIONEINE: A DFT STUDY USING M06, WB97XD AND TPSSTPSS METHODS

2018 ◽  
Vol 54 (2C) ◽  
pp. 299
Author(s):  
Chinh Thi Ngo
Keyword(s):  
Gas Phase ◽  
Antioxidant Properties ◽  
Basis Set ◽  
Bond Dissociation Enthalpy ◽  
Single Electron Transfer ◽  
Dft Methods ◽  
Dissociation Enthalpy ◽  
Proton Dissociation ◽  
B3lyp Method ◽  
Thermochemical Parameters

Antioxidant properties of ergothioneine (ESH) have been investigated via hydrogen atomtransfer (HAT), single electron transfer-proton transfer (SET-PT) and sequential proton losselectron transfer (SPLET) mechanisms. Three new DFT methods including M06, WB97XD andTPSSTPSS at the 6-311++G(2df,2p) basis set were used to compute the thermochemicalparameters of ESH in the gas phase. Based on these methods, bond dissociation enthalpy (BDE),ionization energy (IE), proton dissociation enthalpy (PDE), proton affinity (PA) and electrontransfer enthalpy (ETE) were calculated. The results were also compared with the valuesobtained by B3LYP method. The calculated results show that ergothioneine plays a role as apotential antioxidant via HAT mechanism.

A THEORETICAL STUDY ON THE ANTIOXIDANT PROPERTY OF GALLIC ACID AND ITS DERIVATIVES

2012 ◽  
Vol 11 (02) ◽  
pp. 391-402 ◽  
Author(s):  
DIPIKA KALITA ◽  
RAHUL KAR ◽  
JYOTIREKHA G. HANDIQUE
Keyword(s):  
Phenolic Compounds ◽  
Gallic Acid ◽  
Gas Phase ◽  
Chemical Potential ◽  
Theoretical Study ◽  
Antioxidant Property ◽  
Reactivity Descriptors ◽  
Dissociation Enthalpy ◽  
Local Softness

We analyze the antioxidant property of four phenolic compounds i.e., gallic acid, methyl gallate, ethyl gallate, and 4, 5-dihydroxy 3-methoxy benzoic acid through the determination of bond dissociation enthalpy (BDE), vertical ionization potential ( IP v) in gas phase as well as in six different solvent medium. The theoretical trends of these phenolic compounds, based on BDE and IP, is compared with the scavenging activity towards HOCl . In addition, we compute and analyze the values of the density-based reactivity descriptors such as chemical potential, hardness, electrophilicity, and local softness.

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