Electronic Effects on O−H Proton Dissociation Energies of Phenolic Cation Radicals:  A DFT Study

Zhang, Hongyu; Sun, Yan‐Qiong; Wang, Xiuli

doi:10.1021/jo016234y

Cited by 57 publications

(49 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This trend is opposite to that observed for PAs. It is known that electron-donating groups stabilize ArOH +• but destabilize the parent structure, while electron-withdrawing groups have an opposite effect [15,39,94]. These results are in agreement with previous papers on substituted phenols and chromans.…”

Section: 104supporting

confidence: 93%

“…Electron donating groups have an opposite effect. 15,39,84,85 The present calculated PA for the Magnolol reached 51 kJ mol -1 in water. For Magnolols substituted in meta-and ortho-positions, computed PAs and ΔPAs in the water are reported in Table 4.…”

Section: 104mentioning

confidence: 48%

“…Ionization potential (IP) and proton dissociation enthalpy (PDE) 14,15 represent enthalpies of the SET-PT process. In the SET-PT mechanism, the ionization potential (IP) is the most significant parameter; the lower the IP value, the easier the electron abstraction.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Magnolol Derivatives in the Gas-Phase and Water

Najafi¹,

Najafi²,

Najafi³

2012

Bulletin of the Korean Chemical Society

View full text Add to dashboard Cite

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

show abstract

Section: 104supporting

confidence: 93%

Section: 104mentioning

confidence: 48%

See 1 more Smart Citation

DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Magnolol Derivatives in the Gas-Phase and Water

Najafi¹,

Najafi²,

Najafi³

2012

Bulletin of the Korean Chemical Society

View full text Add to dashboard Cite

show abstract

“…Ionization potential (IP) and proton dissociation enthalpy (PDE) 8,9 represent enthalpies of the SET-PT process. In the SET-PT mechanism, the ionization potential (IP) is the most significant parameter; the lower the IP value, the easier the electron abstraction.…”

Section: Roomentioning

confidence: 99%

DFT/B3LYP Study to Investigate the Possible Ways for the Synthesize of Antioxidants with High Efficiency Based on Vitamin E

Najafi¹,

Najafi²,

Najafi³

2012

Bulletin of the Korean Chemical Society

View full text Add to dashboard Cite

The possible ways for increasing the antioxidant properties of vitamin E have been investigated with density function theory. The effect of replacing three methyl groups of vitamin E with various substituents such as electron donating and electron withdrawing groups on the antioxidant properties of vitamin E were investigated. Also the effects of the reducing the number of atoms in the heterocyclic ring and replacing the oxygen heteroatom with other heteroatoms on the antioxidant properties of vitamin E were investigated. The novel structures that obtained from replacing methyl groups with substituents such as NH 2 , OH, COOH and NHMe have greater antioxidant activity than vitamin E. Obtained results reveal that novel structure that obtained with replacing O with NH hetroatom would be a better antioxidant than vitamin E. The results reveal that reducing the number of atoms in the heterocyclic ring is a better way to synthesize novel antioxidants.

show abstract

“…In fact, comparing the theoretical coupling constants of the neutral and dissociated catechol radicals (the carboxyl group is always considered dissociated), the participation of the excess electron from the phenolate group obviously enhances the overall resonance stabilization (data not shown). Since application of this theoretical approach for more complex structures is still in its infancy, the only comparable studies were carried out for the calculations of the spin densities of three undissociated semiquinone structures of caffeic acid (34) and calculations of bond-dissociation energies of phenolic protons (35,36).…”

Section: Gmentioning

confidence: 99%

Antioxidant Mechanisms of Polyphenolic Caffeic Acid Oligomers, Constituents of Salvia officinalis

et al. 2004

View full text Add to dashboard Cite

Caffeic acid, rosmarinic acid and oligomers of caffeic acid with multiple catechol groups are all constituents of Salvia officinalis. Their antioxidant potential was investigated with regard to their radical scavenging activity and the stability and structure of the intermediate radicals. Pulse-radiolytic studies revealed very high rate constants with hydroxyl radicals. Evidence from kinetic modeling calculations suggested an unusual complex behavior due to the presence of both O 4 -and O 3 -semiquinones and formation and decay of a hydroxyl radical adduct at the vinyl side chain. The radical structures observed by EPR spectroscopy after autoxidation in slightly alkaline solutions were only partially identified due to their instability and generally represented dissociated O 4 -semiquinones. Hybrid density-functional calculations of the potential radical structures showed distinct differences between the resonance stabilization of the O 4 -and O 3 -semiquinones of caffeic and dihydrocaffeic acids, reflected also in the considerably faster decay of the O 3 -semiquinone observed by pulse radiolysis. No evidence was found for dimerization reactions via Cβ radicals typical for lignin biosynthesis.

show abstract

Electronic Effects on O−H Proton Dissociation Energies of Phenolic Cation Radicals: A DFT Study

Cited by 57 publications

References 28 publications

DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Magnolol Derivatives in the Gas-Phase and Water

DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Magnolol Derivatives in the Gas-Phase and Water

DFT/B3LYP Study to Investigate the Possible Ways for the Synthesize of Antioxidants with High Efficiency Based on Vitamin E

Antioxidant Mechanisms of Polyphenolic Caffeic Acid Oligomers, Constituents of Salvia officinalis

Contact Info

Product

Resources

About