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Journal articles on the topic 'Bond dissociation enthalpy'

Author: Grafiati

Published: 4 June 2021

Last updated: 25 May 2024

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1

Mahmood, Asif, Muhammad Saqib, Muhammad Ali, Muhammad Imran Abdullah, and Bilal Khalid. "Theoretical investigation for the designing of novel antioxidants." Canadian Journal of Chemistry 91, no. 2 (February 2013): 126–30. http://dx.doi.org/10.1139/cjc-2012-0356.

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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.

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2

Poliak, Peter, and Adam Vagánek. "Torsional deformation effect on the N—H bond dissociation energy in diphenylamine." Acta Chimica Slovaca 6, no. 2 (October 1, 2013): 182–86. http://dx.doi.org/10.2478/acs-2013-0029.

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Abstract In this work, the influence of the inter-ring dihedral angles and their deformation on the energetics of diphenylamine molecule and its radical is investigated by the B3LYP/6-311++G** approach. Our approximated bond dissociation enthalpy of diphenylamine is 370.0 kJ mol-1 and it is in good agreement with the recently published experimental data. The potential functions of both the molecule and the radical with respect to the mutual aromatic ring orientations are presented. The potential function for the molecule is of a double-barrier type, whereas the radical possesses a single-barrier function. The calculated total electronic energies are used to approximate the change of the bond dissociation enthalpy with the twisting of the dihedral angle. The dependence of the bond dissociation enthalpy on the dihedral angle is represented by a single-barrier type function. The dependence of the nitrogen atom spin density on the studied dihedral angle is also discussed.

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3

Feliciano, Inês O., Daniela P. Silva, M. Fátima M. Piedade, Carlos E. S. Bernardes, and Manuel E. Minas da Piedade. "First and Second Dissociation Enthalpies in Bi-Component Crystals Consisting of Maleic Acid and L-Phenylalanine." Molecules 26, no. 18 (September 21, 2021): 5714. http://dx.doi.org/10.3390/molecules26185714.

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The energetics of the stepwise dissociation of a A:B2 bi-component crystal, according to A:B2(cr) → A:B(cr) + B(cr) and A:B(cr) → A(cr) + B(cr), was investigated using MA:Phe2 and MA:Phe (MA = maleic acid; Phe = L-phenylalanine) as model systems. The enthalpy changes associated with these sequential processes and with the overall dissociation reaction A:B2(cr) → A(cr) + 2B(cr) were determined by solution calorimetry. It was found that they are all positive, indicating that there is a lattice enthalpy gain when MA:Phe2 is formed, either from the individual precursors or by adding Phe to MA:Phe. Single-crystal X-ray diffraction (SCXRD) analysis showed that MA:Phe2 is best described as a protic salt containing a maleate anion (MA−) and two non-equivalent L-phenylalanine units, both linked to MA− by NH···O hydrogen bonds (H-bond): one of these units is protonated (HPhe+) and the other zwitterionic (Phe±). Only MA− and HPhe+ molecules are present in the MA:Phe lattice. In this case, however, NH···O and OH···O H-bonds are formed between each MA− unit and two HPhe+ molecules. Despite these structural differences, the enthalpy cost for the removal of the zwitterionic Phe± unit from the MA:Phe2 lattice to yield MA:Phe is only 0.9 ± 0.4 kJ mol−1 higher than that for the dissociation of MA:Phe, which requires a proton transfer from HPhe+ to MA− and the rearrangement of L-phenylalanine to the zwitterionic, Phe±, form. Finally, a comparison of the dissociation energetics and structures of MA:Phe and of the previously reported glycine maleate (MA:Gly) analogue indicated that parameters, such as the packing coefficient, density, hydrogen bonds formed, or fusion temperature, are not necessarily good descriptors of dissociation enthalpy or lattice enthalpy trends when bi-component crystals with different molecular composition are being compared, even if the stoichiometry is the same.

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4

Tamafo Fouegue, Aymard Didier, Julius Numbonui Ghogomu, Désiré Bikélé Mama, Nyiang Kennet Nkungli, and Elie Younang. "Structural and Antioxidant Properties of Compounds Obtained from Fe2+Chelation by Juglone and Two of Its Derivatives: DFT, QTAIM, and NBO Studies." Bioinorganic Chemistry and Applications 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/8636409.

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The chelating ability of juglone and two of its derivatives towards Fe2+ion and the antioxidant activity (AOA) of the resulting chelates and complexes (in the presence of H2O and CH3OH as ligands) in gas phase is reported via bond dissociation enthalpy, ionization potential, proton dissociation enthalpy, proton affinity, and electron transfer enthalpy. The DFT/B3LYP level of theory associated with the 6-31+G(d,p) and 6-31G(d) Pople-style basis sets on the atoms of the ligands and the central Fe(II), respectively, was used. Negative chelation free energies obtained revealed that juglone derivatives possessing the O-H substituent (L2) have the greatest ability to chelate Fe2+ion. Apart from1B, thermodynamic descriptors of the AOA showed that the direct hydrogen atom transfer is the preferred mechanism of the studied molecules. NBO analysis showed that the Fe-ligand bonds are all formed through metal to ligand charge transfer. QTAIM studies revealed that among all the Fe-ligand bonds, the O1-Fe bond of1Ais purely covalent. The aforementioned results show that the ligands can be used to fight against Fe(II) toxicity, thus preserving human health, and fight against the deterioration of industrial products. In addition, most of the complexes studied have shown a better AOA than their corresponding ligands.

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5

Ngo, Chinh Thi. "THERMOCHEMICAL PARAMETERS OF ERGOTHIONEINE: A DFT STUDY USING M06, WB97XD AND TPSSTPSS METHODS." Vietnam Journal of Science and Technology 54, no. 2C (March 19, 2018): 299. http://dx.doi.org/10.15625/2525-2518/54/2c/11850.

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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.

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6

Zhang, Hong-Yu. "On the O–H bond dissociation enthalpy of catechol." New Journal of Chemistry 27, no. 3 (January 31, 2003): 453–54. http://dx.doi.org/10.1039/b212161c.

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7

Xu, Shenying, Quan-De Wang, Mao-Mao Sun, Guoliang Yin, and Jinhu Liang. "Benchmark calculations for bond dissociation energies and enthalpy of formation of chlorinated and brominated polycyclic aromatic hydrocarbons." RSC Advances 11, no. 47 (2021): 29690–701. http://dx.doi.org/10.1039/d1ra05391d.

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Benchmark calculations using state-of-the-art DFT functionals and composite methods for bond dissociation energy and enthalpy of formation of halogenated polycyclic aromatic hydrocarbons are performed.

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8

Le, Tien Dung. "COMPUTATIONAL STUDY OF MOLECULAR STRUCTURES AND ANTIOXIDANT MECHANISM OF OVOTHIOLS." Vietnam Journal of Science and Technology 54, no. 2C (March 19, 2018): 328. http://dx.doi.org/10.15625/2525-2518/54/2c/11854.

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In this paper, the molecular structure and antioxidant activity of ovothiols (OSH) have beenstudied by using four DFT functionals, namely B3LYP, B3PW91, X3LYP, M06 with the basisset of 6-311++G(2df,2p). Two major antioxidant mechanisms, namely, hydrogen atom transfer(HAT) and stepwise electron transfer-proton transfer (SET-PT) have been investigated andapplied on three optimized conformations of ovothiols. Bond dissociation enthalpy (BDE),vertical ionization energy (IE), proton dissociation enthalpy (PDE), chemical potential (μ),chemical hardness (η) and global electrophilicity (ω), have been calculated and discussed in thegas phase.

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9

NAJAFI, MEYSAM, MOHAMMAD NAJAFI, and HOUSHANG NAJAFI. "THEORETICAL STUDY OF THE SUBSTITUENT EFFECTS ON THE REACTION ENTHALPIES OF THE ANTIOXIDANT MECHANISMS OF STOBADINE DERIVATIVES IN THE GAS-PHASE AND WATER." Journal of Theoretical and Computational Chemistry 12, no. 02 (March 2013): 1250116. http://dx.doi.org/10.1142/s0219633612501167.

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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.

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10

Poła, Andrzej, Anna Palko-Łabuz, and Kamila Środa-Pomianek. "Theoretical Study of 2-(Trifluoromethyl)phenothiazine Derivatives with Two Hydroxyl Groups in the Side Chain-DFT and QTAIM Computations." Molecules 26, no. 17 (August 29, 2021): 5242. http://dx.doi.org/10.3390/molecules26175242.

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Phenothiazines are known as synthetic antipsychotic drugs that exhibit a wide range of biological effects. Their properties result from the structure and variability of substituents in the heterocyclic system. It is known that different quantum chemical properties have a significant impact on drug behavior in the biological systems. Thus, due to the diversity in the chemical structure of phenothiazines as well as other drugs containing heterocyclic systems, quantum chemical calculations provide valuable methods in predicting their activity. In our study, DFT computations were applied to show some thermochemical parameters (bond dissociation enthalpy—BDE, ionization potential—IP, proton dissociation enthalpy—PDE, proton affinity—PA, and electrontransfer enthalpy—ETE) describing the process of releasing the hydrogen/proton from the hydroxyl group in the side chain of four 2-(trifluoromethyl)phenothiazine (TFMP) derivatives and fluphenazine (FLU). Additional theoretical analysis was carried out based on QTAIM theory. The results allowed theoretical determination of the ability of compounds to scavenge free radicals. In addition, the intramolecular hydrogen bond (H-bond) between the H-atom of the hydroxyl group and the N-atom located in the side chain of the investigated compounds has been identified and characterized.

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11

Lucarini, Marco, Gian Franco Pedulli, and Marta Cipollone. "Bond Dissociation Enthalpy of .alpha.-Tocopherol and Other Phenolic Antioxidants." Journal of Organic Chemistry 59, no. 17 (August 1994): 5063–70. http://dx.doi.org/10.1021/jo00096a061.

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12

Škorňa, Peter, Martin Michalík, and Erik Klein. "Gallic acid: thermodynamics of the homolytic and heterolytic phenolic O—H bonds splitting-off." Acta Chimica Slovaca 9, no. 2 (October 1, 2016): 114–23. http://dx.doi.org/10.1515/acs-2016-0020.

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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.

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13

Shaofeng, Li, and G. Pilcher. "Enthalpy of formation of pyridine-N-oxide: the dissociation enthalpy of the (NO) bond." Journal of Chemical Thermodynamics 20, no. 4 (April 1988): 463–65. http://dx.doi.org/10.1016/0021-9614(88)90184-x.

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14

Li, Rui, Tianshu Du, Jingxing Liu, Adelia J. A. Aquino, and Jianyu Zhang. "Theoretical Study of O-CH3 Bond Dissociation Enthalpy in Anisole Systems." ACS Omega 6, no. 34 (August 19, 2021): 21952–59. http://dx.doi.org/10.1021/acsomega.1c02310.

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15

O'Hare, P. A. G., S. Susman, and K. J. Volin. "Thermochemistry of germanium monoselenide, and the GeSe bond dissociation enthalpy." Journal of Chemical Thermodynamics 21, no. 8 (August 1989): 827–36. http://dx.doi.org/10.1016/0021-9614(89)90030-x.

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16

SADASIVAM, K., R. JAYAPRAKASAM, and R. KUMARESAN. "A DFT STUDY ON THE ROLE OF DIFFERENT OH GROUPS IN THE RADICAL SCAVENGING PROCESS." Journal of Theoretical and Computational Chemistry 11, no. 04 (July 16, 2012): 871–93. http://dx.doi.org/10.1142/s0219633612500599.

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The molecular properties of robinetin and melanoxetin which are the two naturally occurring flavonoid compounds have been studied theoretically by means of density functional theory approach (DFT) at the level of B3LYP/6-311G(d,p). The analysis of computed bond dissociation enthalpy (BDE), proton dissociation enthalpy (PDE), proton affinity (PA), electron transfer enthalpy (ETE) values for both the flavonoid compounds indicate the role of B-ring for the significant antioxidant characteristics and the instability of the A-ring. It also concerns the dominant role of BDE mechanism for antioxidant activity than PDE, PA and ETE mechanisms. Ionization potential (IP) is also found to be trustworthy in the study of antioxidant activity and the computed IP magnitudes are in agreement with the values of synthetic food additives. Further, the various molecular descriptors along with the plot of frontier molecular orbitals and Mulliken spin population analysis have been obtained and the validity of Koopmans' theorem is also verified with reference to antioxidant behavior.

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17

Dorofeeva, Olga V., and Oxana N. Ryzhova. "Enthalpy of Formation and O–H Bond Dissociation Enthalpy of Phenol: Inconsistency between Theory and Experiment." Journal of Physical Chemistry A 120, no. 15 (April 11, 2016): 2471–79. http://dx.doi.org/10.1021/acs.jpca.6b02233.

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18

Thbayh, Dalal K., Edina Reizer, Mousumi U. Kahaly, Béla Viskolcz, and Béla Fiser. "Antioxidant Potential of Santowhite as Synthetic and Ascorbic Acid as Natural Polymer Additives." Polymers 14, no. 17 (August 27, 2022): 3518. http://dx.doi.org/10.3390/polym14173518.

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A wide variety of additives are used to improve specific characteristics of the final polymeric product. Antioxidant additives (AAs) can prevent oxidative stress and thus the damage of polymeric materials. In this work, the antioxidant potential and thus the applicability of Santowhite (SW) as synthetic and ascorbic acid (Asc) as natural AAs were explored by using computational tools. Two density functional theory (DFT) methods, M05-2X and M06-2X, have been applied in combination with the 6-311++G(2d,2p) basis set in gas phase. Three antioxidant mechanisms have been considered: hydrogen atom transfer (HAT), single electron transfer-proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET). Bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE) have been computed for each potential hydrogen donor site. The results indicate that the antioxidant potential of Asc is higher than SW. Furthermore, some of the C-H bonds, depending on their position in the structures, are potent radical scavengers, but O-H groups are more prone to donate H-atoms to free radicals. Nonetheless, both additives can be potentially applied to safeguard common polymers and prohibit oxidative stress-induced material deterioration.

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19

Najafi, Mohammad, Meysam Najafi, and Malihe Najafi. "Predicting the substituent and solvent effects on the radical scavenger activity of ethoxyquin derivatives: a DFT/B3LYP study." Canadian Journal of Chemistry 91, no. 6 (June 2013): 457–64. http://dx.doi.org/10.1139/cjc-2013-0049.

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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.

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20

Pop, Raluca, Mariana Ştefănut, Adina Căta, Cristian Tănasie, and Mihai Medeleanu. "Ab initio study regarding the evaluation of the antioxidant character of cyanidin, delphinidin and malvidin." Open Chemistry 10, no. 1 (February 1, 2012): 180–86. http://dx.doi.org/10.2478/s11532-011-0128-1.

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AbstractA theoretical study regarding the evaluation of the antioxidant character of three of the most wide-spread anthocyanidins (cyanidin, delphinidin and malvidin) was carried out at ab initio level. Different parameters (bond dissociation enthalpy, ionization potential, proton affinity, and electron transfer enthalpy) were computed for each OH group of the compounds in order to predict their antioxidant capacity. Several molecular descriptors based on frontier molecular orbital theory (hardness, electrophilicity, frontier charge density) were also calculated, as well as the atomic charges corresponding to the O atoms of the hydroxyl groups.

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21

Bohn, Manfred A., and Thomas M. Klapötke. "DFT and G2MP2 Calculations of the N-N Bond Dissociation Enthalpies and Enthalpies of Formation of Hydrazine, Monomethylhydrazine and Symmetrical and Unsymmetrical Dimethylhydrazine." Zeitschrift für Naturforschung B 59, no. 2 (February 1, 2004): 148–52. http://dx.doi.org/10.1515/znb-2004-0205.

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In a combined DFT (B3LYP) and G2MP2 theoretical study the following enthalpies of formation (ΔH°f) and bond dissociation enthalpies (BDE) for hydrazine, methylhydrazine (MMH), 1,1- dimethylhydrazine (UDMH) and 1,2-dimethylhydrazine (SDMH) were determined: BDE/kJ mol−1: N2H4, 278±4; MMH, 272±4; UDMH, 259±12; SDMH, 272±12. ΔH°f/kJ mol−1: N2H4, 95±6; MMH, 94±4; UDMH, 80±4; SDMH, 91±4. The bond enthalpy for the N-N bond in hydrazine amounts to BE (N-N, H2N−NH2) = 159±4 kJ mol−1.

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22

Zhou, Huakang, Xiangzhou Li, Yaxuan Shang, and Kai Chen. "Radical Scavenging Activity of Puerarin: A Theoretical Study." Antioxidants 8, no. 12 (November 26, 2019): 590. http://dx.doi.org/10.3390/antiox8120590.

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Puerarin is a C-glycoside of daidzein, one of the major bioactive ingredients isolated from the root of Pueraria lobata, which has a wide spectrum of pharmacological effects. Although puerarin is well-known for its effective antioxidant activity, there is seldom a systematic theoretical study on its radical scavenging activity. Herein, the free radical scavenging ability of puerarin was investigated systematically by density functional theory (DFT) calculations. The reaction activity was compared with daidzein as well. Three reaction pathways: hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) were discussed and compared by thermodynamic parameters such as bond dissociation enthalpy (BDE), ionization potential (IP), proton dissociation enthalpy (PDE), proton affinity (PA), and electron transfer enthalpy (ETE). The reaction kinetics of puerarin with special radicals •OH and •OOH were also studied. The results obtained may be of great significance for better understanding the relationship between the antioxidant properties and structural design of puerarin, as well as other antioxidants.

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23

Angel, Laurence A., and Kent M. Ervin. "Competitive Threshold Collision-Induced Dissociation: Gas-Phase Acidity and O−H Bond Dissociation Enthalpy of Phenol." Journal of Physical Chemistry A 108, no. 40 (October 2004): 8346–52. http://dx.doi.org/10.1021/jp0474529.

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24

Da Silva, Manuel A. V. Ribeiro, M. Luisa C. C. H. Ferrão, and Arminda M. L. Magalhães. "Standard enthalpy of formation of tris(2,4-pentanedionato)cobalt(III): The mean (Co-O) bond-dissociation enthalpy." Thermochimica Acta 129, no. 2 (July 1988): 229–35. http://dx.doi.org/10.1016/0040-6031(88)87338-6.

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25

Gomes, José R. B., Maria D. M. C. Ribeiro da Silva, and Manuel A. V. Ribeiro da Silva. "Quinoxaline-1,4-dioxide: Substituent effects on the N–O bond dissociation enthalpy." Chemical Physics Letters 429, no. 1-3 (September 2006): 18–22. http://dx.doi.org/10.1016/j.cplett.2006.07.087.

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26

Nantasenamat, Chanin, Chartchalerm Isarankura-Na-Ayudhya, Thanakorn Naenna, and Virapong Prachayasittikul. "Prediction of bond dissociation enthalpy of antioxidant phenols by support vector machine." Journal of Molecular Graphics and Modelling 27, no. 2 (September 2008): 188–96. http://dx.doi.org/10.1016/j.jmgm.2008.04.005.

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27

Boli, Lusia Silfia Pulo, Nufida Dwi Aisyah, Vera Khoirunisa, Heni Rachmawati, Hermawan Kresno Dipojono, and Febdian Rusydi. "Solvent Effect on Bond Dissociation Enthalpy (BDE) of Tetrahydrocurcumin: A Theoretical Study." Materials Science Forum 966 (August 2019): 215–21. http://dx.doi.org/10.4028/www.scientific.net/msf.966.215.

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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.

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28

Mulder, Peter, Hans-Gert Korth, Derek A. Pratt, Gino A. DiLabio, Luca Valgimigli, G. F. Pedulli, and K. U. Ingold. "Critical Re-evaluation of the O−H Bond Dissociation Enthalpy in Phenol." Journal of Physical Chemistry A 109, no. 11 (March 2005): 2647–55. http://dx.doi.org/10.1021/jp047148f.

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29

ZHOU, WEIDONG, RAY Y. L. CHIM, D. J. COLLINS, and RICHARD P. TUCKETT. "PHOTOELECTRON PHOTOION COINCIDENCE STUDY OF THE FRAGMENTATION OF VALENCE STATES OF CHF2–CH3+ IN THE RANGE 12–25 eV." International Journal of Modern Physics B 23, no. 14 (June 10, 2009): 3073–87. http://dx.doi.org/10.1142/s0217979209052868.

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Using vacuum ultraviolet radiation from a synchrotron source, threshold photoelectron photoion coincidence (TPEPICO) spectroscopy has been used to study the dissociative photoionisation of CHF 2– CH 3 in the photon energy from 11.8 eV to 24.8 eV. Combining with ab initio molecular orbital calculation, fragmentation process and fragmental mechanism of the valence states of parent ion are discussed. For single bond cleavage process, a statistical mechanism might govern the C – C bond cleavage, while the kinetic energy release derived from channel CHF 2– CH 3+ → CH 3– CHF ++ F + e- shows evidence for impulsive mechanism. A two-step increase of signal CF 2– CH 3+/ CHF 2– CH 2+ was observed. The two-step is due to the formation of ion CF 2– CH 3+/ CHF 2– CH 2+ through two different dissociation channels. Both computed molecular orbital character and related G2 dissociation energy support the assumption. The ionisation threshold of 12.02 ± 0.04 eV measured from the TPES and the appearance energies (AEs) identified from the ion yield curves are presented. New or refined upper limit values of enthalpy of formation at 298 K for ion CHF 2+, CF 2– CH 3+ and CHF – CH 3+ are derived.

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30

Najafi, Meysam, and Syed Ali Raza Naqvi. "Theoretical study of the substituent effect on the hydrogen atom transfer mechanism of the irigenin derivatives antioxidant action." Journal of Theoretical and Computational Chemistry 13, no. 02 (March 2014): 1450010. http://dx.doi.org/10.1142/s0219633614500102.

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In this paper, 21 substituents with various electron donating and electron withdrawing characters were placed in available positions of irigenin in order to study their effect on the O – H bond dissociation enthalpy (BDE) via DFT/B3LYP method. Results indicated the substituents in X3 and X4 positions have exerted stronger influence upon BDE values of irigenin derivatives when compared with same substituents in X1 and X2 positions. The results show that intramolecular hydrogen bond effects are able to considerably stabilize the parents and radicals. The natural bond orbital (NBO) analysis results also confirmed the intramolecular hydrogen bond stabilization. The formation of strong intramolecular hydrogen bonds in several radicals results in low BDEs. The 3- OH BDE values for substituents in X2 position have linear dependencies with Hammett constants (Fig. 2 and Eq. (2)). Found dependencies are suitably linear, that can be important for the synthesis of novel antioxidants based on irigenin.

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31

Najafi, Meysam, Mohammad Najafi, and Houshang Najafi. "DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Sesamol Derivatives in the Gas phase and water." Canadian Journal of Chemistry 90, no. 10 (October 2012): 915–26. http://dx.doi.org/10.1139/v2012-087.

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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).

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32

Simões, Ricardo G., Filipe Agapito, Hermínio P. Diogo, and Manuel E. Minas da Piedade. "Enthalpy of Formation of Anisole: Implications for the Controversy on the O–H Bond Dissociation Enthalpy in Phenol." Journal of Physical Chemistry A 118, no. 46 (November 7, 2014): 11026–32. http://dx.doi.org/10.1021/jp507267f.

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33

Biela, Monika, Andrea Kleinová, and Erik Klein. "Thermochemistry of antioxidant action of isoflavones and their deprotonated forms in aqueous solution: hydrogen or electron transfer?" Acta Chimica Slovaca 15, no. 1 (January 1, 2022): 29–35. http://dx.doi.org/10.2478/acs-2022-0004.

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Abstract Isoflavones possessing several weak acidic hydroxyl groups can undergo successive deprotonations in aqueous solutions. Therefore, their antioxidant properties cannot be ascribed only to the neutral forms but also to corresponding phenoxide anions. It was already confirmed that isoflavones prefer the formation of dianions in aqueous solution. For eight isoflavones and their preferred (poly)deprotonated forms, thermochemistry of hydrogen atom transfer and electron abstraction was studied in terms of corresponding reaction enthalpies, i.e., O—H bond dissociation enthalpies and ionization potentials. Our results clearly indicate that the increase in negative charge causes significant drop in ionization potential and bond dissociation enthalpy. On the other hand, proton affinities show the opposite trend. Thus, it is unfeasible to find a generally valid trend for dianions — corresponding reaction enthalpies strongly depend on the structure of isoflavone, especially on the number/positions of OH groups.

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34

Kupaeva, N. V., and E. A. Kotenkova. "Current view on the assessment of antioxidant and antiradical activities: A mini review." IOP Conference Series: Earth and Environmental Science 854, no. 1 (October 1, 2021): 012048. http://dx.doi.org/10.1088/1755-1315/854/1/012048.

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Abstract The main problems in assessing the antioxidant properties of plant biologically active compounds are discussed in this review. Antioxidant potential should be considered as a combination of antioxidant and antiradical activities, since antiradical activity is part of the antioxidant activity and does not always coincide with antioxidant activity. The mechanisms of action and the existing experimental and computational methods for their evaluation were reviewed. Methods like FRAP, CUPRAC etc. could be used for assessment of antioxidant activity of plant compounds, but it is necessary to perform studies on cell cultures or laboratory animals in order to determine mechanisms of action on the antioxidant system of a living organism. The current methodological approaches for studying antiradical activity and its mechanisms include experimental methods such as DPPH, ABTS and ORAC, and computational methods based on density functional theory. The main thermodynamic parameters for evaluating antiradical mechanisms (HAT, SET-PT and SPLET) are the bond dissociation enthalpy, ionization potential, proton dissociation enthalpy, proton affinity, and electron transfer enthalpy, among others. The existing approaches for determining the antiradical mechanisms of antioxidants are quite informative, but can still cannot predict or determine by in vitro methods the antioxidant mechanism of these compounds in organisms consisting of many complex individual systems.

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35

Ribeiro da Silva, Manuel A. V., Maria Luísa C. C. H. Ferrão, and Rosa M. G. Esteves da Silva. "Standard molar enthalpy of formation of tris(3-methylpentane-2,4-dionato)iron(III): the mean (FeO) bond-dissociation enthalpy." Journal of Chemical Thermodynamics 24, no. 12 (December 1992): 1293–98. http://dx.doi.org/10.1016/s0021-9614(05)80269-1.

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36

Khoirunisa, Vera, Lusia Silfia Pulo Boli, Rizka Nur Fadilla, Adhitya Gandaryus Saputro, Heni Rachmawati, Hermawan Kresno Dipojono, and Febdian Rusydi. "Predicting Notable Radical Scavenging Sites of Gnetin C Using Density Functional Theory." Materials Science Forum 966 (August 2019): 229–33. http://dx.doi.org/10.4028/www.scientific.net/msf.966.229.

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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.

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37

Mic, Mihaela, Adrian Pîrnău, Călin G. Floare, Raluca Borlan, Monica Focsan, Ovidiu Oniga, Mircea Bogdan, Laurian Vlase, Ilioara Oniga, and Gabriel Marc. "Antioxidant Activity Evaluation and Assessment of the Binding Affinity to HSA of a New Catechol Hydrazinyl-Thiazole Derivative." Antioxidants 11, no. 7 (June 24, 2022): 1245. http://dx.doi.org/10.3390/antiox11071245.

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Polyphenols have attained pronounced attention due to their ability to provide numerous health benefits and prevent several chronic diseases. In this study, we designed, synthesized and analyzed a water-soluble molecule presenting a good antioxidant activity, namely catechol hydrazinyl-thiazole (CHT). This molecule contains 3′,4′-dihydroxyphenyl and 2-hydrazinyl-4-methyl-thiazole moieties linked through a hydrazone group with very good antioxidant activity in the in vitro evaluations performed. A preliminary validation of the CHT developing hypothesis was performed evaluating in silico the bond dissociation enthalpy (BDE) of the phenol O-H bonds, compared to our previous findings in the compounds previously reported by our group. In this paper, we report the binding mechanism of CHT to human serum albumin (HSA) using biophysical methods in combination with computational studies. ITC experiments reveal that the dominant forces in the binding mechanism are involved in the hydrogen bond or van der Waals interactions and that the binding was an enthalpy-driven process. NMR relaxation measurements were applied to study the CHT–protein interaction by changing the drug concentration in the solution. A molecular docking study added an additional insight to the experimental ITC and NMR analysis regarding the binding conformation of CHT to HSA.

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38

Nam, Pham Cam, and Minh Tho Nguyen. "The Se–H bond of benzeneselenols (ArSe-H): Relationship between bond dissociation enthalpy and spin density of radicals." Chemical Physics 415 (March 2013): 18–25. http://dx.doi.org/10.1016/j.chemphys.2013.02.008.

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39

Martínez-Cifuentes, Maximiliano, Boris Weiss-López, and Ramiro Araya-Maturana. "Theoretical Study about the Effect of Halogen Substitution on the Reactivity of Antitumor 3-Formylchromones and Their Free Radicals." Journal of Chemistry 2017 (2017): 1–5. http://dx.doi.org/10.1155/2017/9254831.

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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.

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40

KALITA, DIPIKA, RAHUL KAR, and JYOTIREKHA G. HANDIQUE. "A THEORETICAL STUDY ON THE ANTIOXIDANT PROPERTY OF GALLIC ACID AND ITS DERIVATIVES." Journal of Theoretical and Computational Chemistry 11, no. 02 (April 2012): 391–402. http://dx.doi.org/10.1142/s0219633612500277.

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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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41

Jiang, Yuqin, Huaqiang Zhanga, Xiangjian Wan, Xiaosong Xue, Yuanhai Liu, Haibin Song, Ao Yu, and Yongsheng Chena. "2,5,8-Tri-tert-butyl-1,3,4,6,7,9-hexaazaphenalene: Synthesis, Crystal Structure and Calculation of Homolytic N–H Bond Dissociation Enthalpies." Zeitschrift für Naturforschung B 63, no. 12 (December 1, 2008): 1425–30. http://dx.doi.org/10.1515/znb-2008-1214.

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2,5,8-Tri-tert-butyl-1,3,4,6,7,9-hexaazaphenalene (6) was prepared from diethyl 2-[bis(methylsulfanyl) methylene]malonate (1) in four steps. The structure of compound 6 was confirmed by single crystal X-ray diffraction. The phenalene skeleton is nearly planar, and there is no π-π overlap between the hexaazaphenalene rings. A calculation of the homolytic bond dissociation enthalpy (BDE) was performed for compound 6 and its analogs 7 and 8, and the results were used to explain the different reactivity for these three compounds to form the corresponding radicals.

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42

Wei, Jing, Qian Liang, Yuxin Guo, Weimin Zhang, and Long Wu. "A Deep Insight in the Antioxidant Property of Carnosic Acid: From Computational Study to Experimental Analysis." Foods 10, no. 10 (September 26, 2021): 2279. http://dx.doi.org/10.3390/foods10102279.

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Since the deep cause for the anti-oxidation of carnosic acid (CA) against oleic acid (OA) remains unclear, we focused on exploring the CA inhibition mechanism via a combined experimental and computational study. Atomic charge, total molecular energy, phenolic hydroxyl bond dissociation enthalpy (BDE), the highest occupied molecular orbital (HOMO), and the lowest unoccupied orbital (LUMO) energy were first discussed by the B3LYP/6-31G (d,p) level, a density functional method. A one-step hydrogen atom transfer (HAT) was proposed for the anti-oxidation of CA towards OA, and the Rancimat method was carried out for analyzing the thermal oxidation stability. The results indicate that the two phenolic hydroxyl groups located at C7(O15) and C8(O18) of CA exert the highest activity, and the chemical reaction heat is minimal when HAT occurs. Consequently, the activity of C7(O15) (303.27 kJ/mol) is slightly lower than that of C8(O18) (295.63 kJ/mol), while the dissociation enthalpy of phenol hydroxyl groups is much lower than those of α-CH2 bond of OA (C8, 353.92 kJ/mol; C11, 353.72 kJ/mol). Rancimat method and non-isothermal differential scanning calorimetry (DSC) demonstrate that CA outcompetes tertiary butylhydroquinone (TBHQ), a synthetic food grade antioxidant, both in prolonging the oxidation induction period and reducing the reaction rate of OA. The Ea (apparent activation energies of reaction) of OA, TBHQ + OA, and CA + OA were 50.59, 57.32 and 66.29 kJ/mol, revealing that CA could improve the Ea and thermal oxidation stability of OA.

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43

Zhang, Rui-zhou, Xiao-hong Li, and Xian-zhou Zhang. "Theoretical Study of the CCl Bond Dissociation Enthalpy and Electronic Structure of Substituted Chlorobenzene Compounds." Chinese Journal of Chemical Physics 22, no. 3 (June 2009): 235–40. http://dx.doi.org/10.1088/1674-0068/22/03/235-240.

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44

Sun, Youmin, Dezhan Chen, and Chengbu Liu. "Evaluation of the effectiveness of AM1 geometry used in calculating O–H bond dissociation enthalpy." Journal of Molecular Structure: THEOCHEM 618, no. 3 (November 2002): 181–89. http://dx.doi.org/10.1016/s0166-1280(02)00523-7.

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45

Sun, You-Min, Hong-Yu Zhang, and De-Zhan Chen. "Evaluation of a Combined Quantum Chemical Method Used in Calculating OH Bond Dissociation Enthalpy." Chinese Journal of Chemistry 19, no. 7 (August 26, 2010): 657–61. http://dx.doi.org/10.1002/cjoc.20010190706.

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46

Mendiara, S. N., and M. E. J. Coronel. "EPR Equilibration Study of the O–H Bond Dissociation Enthalpy in a Benzyl Phenolic Antioxidant." Applied Magnetic Resonance 33, no. 4 (May 2008): 341–49. http://dx.doi.org/10.1007/s00723-008-0065-0.

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47

Jiao, Peilei, Wenrui Zheng, Ziwen Guan, Lin He, Cuicui Zhang, and Jiaying Tang. "Theoretical study on the P–N bond dissociation enthalpy in phosphamide and phosphoramidate flame retardants." Journal of the Indian Chemical Society 101, no. 1 (January 2024): 101114. http://dx.doi.org/10.1016/j.jics.2023.101114.

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48

Wang, Hui, Yiyu Feng, Huitao Yu, Liqi Dong, Fei Zhai, Junwen Tang, Jing Ge, and Wei Feng. "Utilisation of photo-thermal energy and bond enthalpy based on optically triggered formation and dissociation of coordination bonds." Nano Energy 89 (November 2021): 106401. http://dx.doi.org/10.1016/j.nanoen.2021.106401.

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49

Greenberg, Arthur, Alexa R. Green, and Joel F. Liebman. "Computational Study of Selected Amine and Lactam N-Oxides Including Comparisons of N-O Bond Dissociation Enthalpies with Those of Pyridine N-Oxides." Molecules 25, no. 16 (August 14, 2020): 3703. http://dx.doi.org/10.3390/molecules25163703.

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A computational study of the structures and energetics of amine N-oxides, including pyridine N-oxides, trimethylamine N-oxide, bridgehead bicyclic amine N-oxides, and lactam N-oxides, allowed comparisons with published experimental data. Most of the computations employed the B3LYP/6-31G* and M06/6-311G+(d,p) models and comparisons were also made between the results of the HF 6-31G*, B3LYP/6-31G**, B3PW91/6-31G*, B3PW91/6-31G**, and the B3PW91/6-311G+(d,p) models. The range of calculated N-O bond dissociation energies (BDE) (actually enthalpies) was about 40 kcal/mol. Of particular interest was the BDE difference between pyridine N-oxide (PNO) and trimethylamine N-oxide (TMAO). Published thermochemical and computational (HF 6-31G*) data suggest that the BDE of PNO was only about 2 kcal/mol greater than that of TMAO. The higher IR frequency for N-O stretch in PNO and its shorter N-O bond length suggest a greater difference in BDE values, predicted at 10–14 kcal/mol in the present work. Determination of the enthalpy of sublimation of TMAO, or at least the enthalpy of fusion and estimation of the enthalpy of vaporization might solve this dichotomy. The “extra” resonance stabilization in pyridine N-oxide relative to pyridine was consistent with the 10–14 kcal/mol increase in BDE, relative to TMAO, and was about half the “extra” stabilization in phenoxide, relative to phenol or benzene. Comparison of pyridine N-oxide with its acyclic model nitrone (“Dewar-Breslow model”) indicated aromaticity slightly less than that of pyridine.

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50

Cotes, Sandra, José Cotuá, and Amner Muñoz. "Calculated antioxidant activity of selected phenolic compounds." Canadian Journal of Chemistry 96, no. 3 (March 2018): 345–50. http://dx.doi.org/10.1139/cjc-2017-0496.

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Determination of the corresponding bond dissociation enthalpy, ionization potential and proton affinity, dipole moment values, highest occupied molecular orbital eigenvalues, and spin density along with the bioactivity score is central to the antioxidant activity evaluation in this paper. Molecular geometries were optimized with DFT using B3LYP and UB3LYP for parent, ionic, and radical species and 6-311+G(d,p) basis set. Bioactivity, drug likeness, and drug scores were calculated using freely available cheminformatics programs for data visualization and analysis. Overall, the values revealed two structures as promising molecules because of good reaction enthalpies (ΔHr). Lipinski rules were fully satisfied for all molecules.

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