Theoretical investigation for the designing of novel antioxidants

2013 ◽  
Vol 91 (2) ◽  
pp. 126-130 ◽  
Author(s):  
Asif Mahmood ◽  
Muhammad Saqib ◽  
Muhammad Ali ◽  
Muhammad Imran Abdullah ◽  
Bilal Khalid
Keyword(s):  
Antioxidant Activity ◽  
Salicylic Acid ◽  
Ionization Potential ◽  
Theoretical Investigation ◽  
Heterocyclic Ring ◽  
Hydroxyl Groups ◽  
Bond Dissociation Enthalpy ◽  
Bond Dissociation ◽  
Dissociation Enthalpy ◽  
Spin Densities

In this study, the antioxidant potential of salicylic acid and its derivatives was determined. O–H bond dissociation enthalpy ionization potential and spin densities were computed, which are important characteristics of antioxidants. We have designed new antioxidants on the basis of information obtained from the results of this study and a literature review. O–H bond dissociation enthalpy, ionization potential, and spin densities of designed compounds were also calculated to analyze the effect of the size of the heterocyclic ring, the electronegativity of the heteroatom, the number of hydroxyl groups, and intramolecular hydrogen bonding. The results reveal that compounds with a larger heterocyclic ring, fewer electronegative atoms, and greater number of hydroxyl groups have enhanced antioxidant activity. A comparison of bond dissociation enthalpy of designed compounds IIIA and IV with that of phenolic acid antioxidants shows that these designed compounds are potent antioxidants. From statistical analysis, it is found that for designed compounds, good correlation was found between spin density and bond dissociation enthalpy. The present theoretical investigation will provide help to understand the biological activity of salicylic acid and its derivatives for better utilization in the fields of pharmacy and the food industry. New antioxidants with better antioxidant activity can be synthesized on the basis of the results of this study.

Solvent Effect on Bond Dissociation Enthalpy (BDE) of Tetrahydrocurcumin: A Theoretical Study

2019 ◽  
Vol 966 ◽  
pp. 215-221
Author(s):  
Lusia Silfia Pulo Boli ◽  
Nufida Dwi Aisyah ◽  
Vera Khoirunisa ◽  
Heni Rachmawati ◽  
Hermawan Kresno Dipojono ◽  
...  
Keyword(s):  
Antioxidant Activity ◽  
Solvent Effect ◽  
Functional Groups ◽  
Density Functional ◽  
Hydrogen Transfer ◽  
Bond Dissociation Enthalpy ◽  
Polar Medium ◽  
Bond Dissociation ◽  
Dissociation Enthalpy ◽  
Frequency Calculation

Solvent effect on bond dissociation enthalpy (BDE) of different functional groups of tetrahydrocurcumin is investigated. This is to evaluate how the polarity of a medium affect BDE and to clarify which functional groups hold the key role in its antioxidant activity through hydrogen transfer. We occupy density functional theory to calculate BDE through geometrical optimization and frequency calculation at six sites of tetrahydrocurcumin in water, methanol and chloroform solvents. The solvents represent polar and non-polar medium. Our result shows that BDE is lower in non-polar medium and hydrogen transfer is favored in this medium. A phenolic group is responsible for the antioxidant activity of tetrahydrocurcumin.

Predicting the substituent and solvent effects on the radical scavenger activity of ethoxyquin derivatives: a DFT/B3LYP study

2013 ◽  
Vol 91 (6) ◽  
pp. 457-464
Author(s):  
Mohammad Najafi ◽  
Meysam Najafi ◽  
Malihe Najafi
Keyword(s):  
Ionization Potential ◽  
Gas Phase ◽  
Proton Affinity ◽  
Hydrogen Atom Transfer ◽  
Radical Scavenger ◽  
Bond Dissociation Enthalpy ◽  
Bond Dissociation ◽  
Dissociation Enthalpy ◽  
Radical Scavenger Activity ◽  
Scavenger Activity

The radical scavenger activity of X1- and X2-substituted ethoxyquin derivatives has been investigated in the gas phase and water. The reaction enthalpies of radical scavenger activity of the studied derivatives have been calculated and compared with corresponding values of ethoxyquin. Results show that electron-withdrawing group substituents increase the bond dissociation enthalpy and ionization potential, while electron-donating group substituents cause a rise in the proton affinity. The ethoxyquin derivatives with the lowest bond dissociation enthalpy, ionization potential, and proton affinity values were identified as the compounds with high radical scavenger activity. Results show that the substituents in the X1 position have high potential for synthesis of novel ethoxyquin derivatives. Results show that ethoxyquin derivatives can process their protective role via hydrogen atom transfer and sequential proton loss electron transfer mechanisms in the gas phase and solvent, respectively. The calculated reaction enthalpies of the substituted ethoxyquins have linear dependences with Hammett constants and energy of the highest occupied molecular orbital that can be utilized in the selection of suitable substituents for the synthesis of novel radical scavengers based on ethoxyquin.

Sublimation study of triphenyl boron and the bond-dissociation enthalpy of BC6H5

1984 ◽  
Vol 16 (8) ◽  
pp. 703-709 ◽  
Author(s):  
Steven W. Govorchin ◽  
Adli S. Kana'an ◽  
Joseph M. Kanamueller
Keyword(s):  
Bond Dissociation Enthalpy ◽  
Bond Dissociation ◽  
Dissociation Enthalpy

Enthalpy of Formation of Anisole: Implications for the Controversy on the O–H Bond Dissociation Enthalpy in Phenol

2014 ◽  
Vol 118 (46) ◽  
pp. 11026-11032 ◽  
Author(s):  
Ricardo G. Simões ◽  
Filipe Agapito ◽  
Hermínio P. Diogo ◽  
Manuel E. Minas da Piedade
Keyword(s):  
Enthalpy Of Formation ◽  
Bond Dissociation Enthalpy ◽  
Bond Dissociation ◽  
Dissociation Enthalpy

Thermochemical parameters for organic radicals and radical ions. Part 3. The relationship between bond dissociation enthalpy and radical stability in alkyl systems

1984 ◽  
Vol 62 (9) ◽  
pp. 1850-1859 ◽  
Author(s):  
A. Martin de P. Nicholas ◽  
Donald R. Arnold
Keyword(s):  
Closed Shell ◽  
Bond Dissociation Enthalpy ◽  
Methyl Radical ◽  
Bond Dissociation ◽  
Secondary Bonds ◽  
Dissociation Enthalpy ◽  
Relative Stabilization ◽  
Stabilization Energies ◽  
Thermochemical Parameters ◽  
The Relationship

The relationship between radical stability and bond dissociation enthalpy (BDH) is reexamined. It is shown that relative stabilization energies of radicals are not equal to relative BDH values. Net stabilization energies of radicals, SE0[R•, RX] are defined relative to the R components of closed shell species RX (R(RX)). These components are chosen such that they contain the same (or, approximately the same) net charge as that of the radical (R•). The following results, relative to R = C2H5, were obtained: R•, SE0[R•, RX](kJ mol−1) for X = R (i.e., the dimer RR), CH3, and H; CH3•, 23, 32, 37; n-C3H7•, −2, −2, −3; i-C3H7•, −9, −14, −19; t-C4H9•, −25, −32, −38. These results show that the methyl radical is more destabilized and the n-propyl-, i-propyl-, and tert-butyl radicals are more stabilized than is predicted from the corresponding relative BDH (R—X) values. The intrinsic C—H bond strengths of chosen alkanes are considered. Relative to the C—H bond in ethane, the bond in methane is found to be weaker by 8.12 kJ mol−1 and the primary and secondary bonds in propane and the tertiary bond in methyl propane are stronger by 2.56, 7.98, and 17.12 kJ mol−1 respectively.

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