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Bräkling S, Kroll K, Klee S, Benter T, Kersten H. Hydrogen Plasma-Based Medium Pressure Chemical Ionization Source for GC-TOFMS. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:499-509. [PMID: 35164508 DOI: 10.1021/jasms.1c00329] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The construction, critical evaluation, and performance assessment of a medium-pressure (2-13 mbar), high-temperature chemical ionization (CI) source for application in GC-MS is described. The ion source is coupled to a commercial time-of-flight (TOF) mass analyzer. Reagent ions are generated in a two staged process. The first stage uses a filament free, helical resonator plasma (HRP) driven ion source for H3+ generation. Reagent gases, for example, nitrogen, isobutane, and methane are added in a second stage to the H3+ stream, which leads to the formation of final protonation reagents. The GC effluent is added subsequently to the reagent ion gas stream. Designed for the hyphenation with gas chromatography, this GC-CI-TOFMS combination produces GC limited Gaussian peak shapes even for high boiling point compounds. Limits of detection for the compounds investigated are determined as 0.4-1.2 pg on column with nitrogen, 0.6-12.6 pg with isobutane, and 2 pg to >25 pg with methane as reagent gas, respectively. An EPA 8270 LCS mix containing 78 main EPA pollutants is used to evaluate the selectivity of the different reagent ions. Using nitrogen as reagent gas, 74 of 78 compounds are detected. In comparison, 41 of 78 compounds and 62 of 78 compounds are detected with isobutane or methane as CI reagent gas, respectively.
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Affiliation(s)
- Steffen Bräkling
- TOFWERK AG, 3645 Thun, Switzerland
- Department of Physical and Theoretical Chemistry, University of Wuppertal, 42119 Wuppertal, Germany
| | - Kai Kroll
- Department of Physical and Theoretical Chemistry, University of Wuppertal, 42119 Wuppertal, Germany
| | | | - Thorsten Benter
- Department of Physical and Theoretical Chemistry, University of Wuppertal, 42119 Wuppertal, Germany
| | - Hendrik Kersten
- Department of Physical and Theoretical Chemistry, University of Wuppertal, 42119 Wuppertal, Germany
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2
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Braga LS, Henriques Soares Leal D, Ramalho TC. Rationalising the regioselectivity of substituted phenols from the FERMO concept: stereoelectronic effects on protonation and functionalization. MOLECULAR SIMULATION 2022. [DOI: 10.1080/08927022.2022.2039390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
| | | | - Teodorico Castro Ramalho
- Department of Chemistry, Federal University of Lavras, Lavras, Brazil
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic
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Tukumova NV, Belova NV, Usacheva TR, Thuan TTD. Structural–Thermodynamic Characteristics of Maleic Acid in Water–Organic Solvents. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2021. [DOI: 10.1134/s0036024421070268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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4
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Braga LS, Leal DHS, Kuca K, Ramalho TC. Perspectives on the Role of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) in the Study of Chemical Reactivity: An Updated Review. CURR ORG CHEM 2020. [DOI: 10.2174/1385272824666200204121044] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Molecular orbitals are critical in the rationalization of several chemical reactions.
Thus, the frontier molecular orbital theory, proposed by Fukui's group, postulated
the importance of the Highest Occupied Molecular Orbital (HOMO) and the Lowest Unoccupied
Molecular Orbital (LUMO) for chemical reactions. It should be kept in mind,
however, that there are limitations of this theory and new perspectives about the chemical
reactivity have recently been arisen based on composition and location of other frontier
molecular orbitals. In this review, we have reported the development and the most recent
applications of the Frontier Effective-for-Reaction Molecular Orbital (FERMO) concept,
which describes the breaking and formation of new chemical bonds and can in turn, provide
important clues that modulate chemical reactivity of atoms and molecules.
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Affiliation(s)
- Letícia S. Braga
- Department of Chemistry, Federal University of Lavras, Lavras, Brazil
| | - Daniel H. S. Leal
- Institute of Physics and Chemistry, Federal University of Itajuba, Itajuba, Brazil
| | - Kamil Kuca
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic
| | - Teodorico C. Ramalho
- Department of Chemistry, Faculty of Science, University of Hradec Kralove, Hradec Kralove, Czech Republic
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5
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Antioxidants and antioxidant methods: an updated overview. Arch Toxicol 2020; 94:651-715. [PMID: 32180036 DOI: 10.1007/s00204-020-02689-3] [Citation(s) in RCA: 684] [Impact Index Per Article: 171.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2020] [Accepted: 02/24/2020] [Indexed: 02/07/2023]
Abstract
Antioxidants had a growing interest owing to their protective roles in food and pharmaceutical products against oxidative deterioration and in the body and against oxidative stress-mediated pathological processes. Screening of antioxidant properties of plants and plant-derived compounds requires appropriate methods, which address the mechanism of antioxidant activity and focus on the kinetics of the reactions including the antioxidants. Many studies evaluating the antioxidant activity of various samples of research interest using different methods in food and human health have been conducted. These methods are classified, described, and discussed in this review. Methods based on inhibited autoxidation are the most suited for termination-enhancing antioxidants and for chain-breaking antioxidants, while different specific studies are needed for preventive antioxidants. For this purpose, the most common methods used in vitro determination of antioxidant capacity of food constituents were examined. Also, a selection of chemical testing methods was critically reviewed and highlighted. In addition, their advantages, disadvantages, limitations and usefulness were discussed and investigated for pure molecules and raw extracts. The effect and influence of the reaction medium on the performance of antioxidants are also addressed. Hence, this overview provides a basis and rationale for developing standardized antioxidant methods for the food, nutraceuticals, and dietary supplement industries. In addition, the most important advantages and shortcomings of each method were detected and highlighted. The chemical principles of these methods are outlined and critically discussed. The chemical principles of methods of 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulphonate) radical (ABTS·+) scavenging, 1,1-diphenyl-2-picrylhydrazyl (DPPH·) radical scavenging, Fe3+-Fe2+ transformation assay, ferric reducing antioxidant power (FRAP) assay, cupric ions (Cu2+) reducing power assay (Cuprac), Folin-Ciocalteu reducing capacity (FCR assay), peroxyl radical (ROO·), superoxide radical anion (O2·-), hydrogen peroxide (H2O2) scavenging assay, hydroxyl radical (OH·) scavenging assay, singlet oxygen (1O2) quenching assay, nitric oxide radical (NO·) scavenging assay and chemiluminescence assay are outlined and critically discussed. Also, the general antioxidant aspects of main food components were discussed by a number of methods, which are currently used for the detection of antioxidant properties of food components. This review consists of two main sections. The first section is devoted to the main components in the food and pharmaceutical applications. The second general section comprises some definitions of the main antioxidant methods commonly used for the determination of the antioxidant activity of components. In addition, some chemical, mechanistic and kinetic basis, and technical details of the used methods are given.
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dos Santos Pereira AK, Nakahata DH, Manzano CM, de Alencar Simoni D, Pereira DH, Lustri WR, Formiga ALB, Corbi PP. Synthesis, crystallographic studies, molecular modeling and in vitro biological studies of silver(I) complexes with aminoadamantane ligands. Polyhedron 2019. [DOI: 10.1016/j.poly.2019.114116] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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7
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DFT study of the application of polymers cellulose and cellulose acetate for adsorption of metal ions (Cd2+, Cu2+ and Cr3+) potentially toxic. Polym Bull (Berl) 2019. [DOI: 10.1007/s00289-019-02926-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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8
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El Guesmi N, Boubaker T, Goumont R, Terrier F. Regioselectivity and High Electrophilicity in the σ Complexation of Aromatic Triflones. European J Org Chem 2014. [DOI: 10.1002/ejoc.201402607] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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9
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Ivanov SN, Giricheva NI, Nurkevich TV, Fedorov MS. Energies of the gas-phase deprotonation of nitro-substituted benzenesulfonic and benzoic acids: The role of the conformation isomerism of sulfonic acids. RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A 2014. [DOI: 10.1134/s0036024414040104] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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FARMANZADEH DAVOOD, NAJAFI MEYSAM. ANTIOXIDANT ACTIVITY OF AMINOTHIAZOL HYDROXYCOUMARIN DERIVATIVES. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2013. [DOI: 10.1142/s0219633613500582] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In this work, the antioxidant properties of the series of 10 aminothiazol hydroxyl coumarin derivatives have been investigated with DFT/B3LYP method. For these antioxidants all reaction enthalpies related to HAT, SPLET, SET-PT mechanisms were calculated in the gas phase and polar solvents. Based on calculated reaction enthalpies (BDE, IP and PA values) the derivations 2, 3 and 4 have the highest antioxidant activity among the studied compounds. Calculated results show that derivations 7, 5 and 6 have the lowest antioxidant activity. The observed theoretical trends for antioxidant activities of studied compounds were similar to trends of previous experimental studies that OH50, TAC50, IC50, CE50 values have been used as a benchmark for measuring the antioxidant properties of these compounds. These results can be useful in synthesis of novel aminothiazol hydroxycoumarin derivatives with high antioxidant activity. Calculated results show that BDE, PA and IP values of studied derivations have linear dependence with structure parameters such as R( O – H ), q( O ) and E HOMO . These observed linear dependences can be useful in synthesis of novel aminothiazol hydroxyl coumarin derivatives with high antioxidant activity. For studied compounds, results indicated that the SPLET and HAT mechanisms represent the thermodynamically preferred mechanism both, in solvent and the gas phase.
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Affiliation(s)
- DAVOOD FARMANZADEH
- Department of Physical Chemistry, Faculty of Chemistry, University of Mazandaran, Babolsar 47416-95447, Islamic Republic of Iran
| | - MEYSAM NAJAFI
- Department of Physical Chemistry, Faculty of Chemistry, University of Mazandaran, Babolsar 47416-95447, Islamic Republic of Iran
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Bizier NP, Wackerly JW, Braunstein ED, Zhang M, Nodder ST, Carlin SM, Katz JL. An Alternative Role for Acetylenes: Activation of Fluorobenzenes toward Nucleophilic Aromatic Substitution. J Org Chem 2013; 78:5987-98. [PMID: 23692440 DOI: 10.1021/jo400668v] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Nicholas P Bizier
- Department of Chemistry, Colby College, 5754 Mayflower Hill Drive, Waterville, Maine 04901, United States
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12
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Najafi M, Najafi M, Najafi H. Theoretical Study of the Substituent and Solvent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Tyrosol Derivatives. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2013. [DOI: 10.1246/bcsj.20120265] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Meysam Najafi
- Department of Mathematics, Anar Branch, Islamic Azad University
| | - Mohammad Najafi
- Department of Mathematics, Anar Branch, Islamic Azad University
| | - Houshang Najafi
- Department of Physiology, Faculty of Medicine, Kermanshah University of Medical Sciences
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NAJAFI MEYSAM, NAJAFI MOHAMMAD, NAJAFI HOUSHANG. 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 & COMPUTATIONAL CHEMISTRY 2013. [DOI: 10.1142/s0219633612501167] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
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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Affiliation(s)
- MEYSAM NAJAFI
- Department of Physiology, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - MOHAMMAD NAJAFI
- Department of Physiology, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - HOUSHANG NAJAFI
- Department of Physiology, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
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14
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Najafi M, Najafi M, Najafi H. DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Magnolol Derivatives in the Gas-Phase and Water. B KOREAN CHEM SOC 2012. [DOI: 10.5012/bkcs.2012.33.11.3607] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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15
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Najafi M, Najafi M, Najafi H. DFT/B3LYP study of the substituent effects on the reaction enthalpies of the antioxidant mechanisms of Indole-3-Carbinol derivatives in the gas-phase and water. COMPUT THEOR CHEM 2012. [DOI: 10.1016/j.comptc.2012.08.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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16
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Najafi M, Najafi M, Najafi H. DFT/B3LYP Study to Investigate the Possible Ways for the Synthesize of Antioxidants with High Efficiency Based on Vitamin E. B KOREAN CHEM SOC 2012. [DOI: 10.5012/bkcs.2012.33.10.3343] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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17
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Najafi M, Najafi M, Najafi H. DFT/B3LYP Study of the Substituent Effects on the Reaction Enthalpies of the Antioxidant Mechanisms of Sesamol Derivatives in the Gas phase and water. CAN J CHEM 2012. [DOI: 10.1139/v2012-087] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
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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Affiliation(s)
- Meysam Najafi
- Department of Physiology, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Mohammad Najafi
- Department of Physiology, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
| | - Houshang Najafi
- Department of Physiology, Faculty of Medicine, Kermanshah University of Medical Sciences, Kermanshah, Iran
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Derbel N, Clarot I, Mourer M, Regnouf-de-Vains JB, Ruiz-López MF. Intramolecular interactions versus hydration effects on p-guanidinoethyl-phenol structure and pKa values. J Phys Chem A 2012; 116:9404-11. [PMID: 22931189 DOI: 10.1021/jp3069893] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We analyze the structure, hydration, and pK(a) values of p-guanidinoethyl-phenol through a combined experimental and theoretical study. These issues are relevant to understand the mechanism of action of the tetrameric form, the antibacterial compound tetra-p-guanidinoethyl-calix[4]arene (Cx1). The investigated system can also be useful to model other pharmaceutical drugs bearing a guanidine function in the vicinity of an ionizable group and the effect of arginine on the pK(a) of vicinal ionizable residues (in particular tyrosine) in peptides. The p-guanidinoethyl-phenol monomer (mCx1) has two ionizable groups. One important particularity of this system is that it exhibits high molecular flexibility that potentially leads to enhanced stabilization in folded structures by direct, strong Coulombic interactions between the ionizable groups. The first pK(a) corresponding to ionization of the -OH group has experimentally been shown to be only slightly different from usual values in substituted phenols. However, because of short-range Coulombic interactions, the role of intramolecular interactions and solvation effects on the acidities of this compound is expected to be important and it has been analyzed here on the basis of theoretical calculations. We use a discrete-continuum solvation model together with quantum-mechanical calculations at the B3LYP level of theory and the extended 6-311+G(2df,2p) basis set. Both intra- and intermolecular effects are very large (~70 kcal/mol) but exhibit an almost perfect compensation, thus explaining that the actual pK(a) of mCx1 is close to free phenol. The same compensation of environmental effects applies to the second pK(a) that concerns the guanidinium group. Such a pK(a) could not be determined experimentally with standard titration techniques and in fact the theoretical study predicts a value of 14.2, that is, one unit above the pK(a) of the parent ethyl-guanidinium molecule.
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Affiliation(s)
- Najoua Derbel
- LSAMA, University of Tunis - El Manar, Campus Universitaire, 2092, Tunis, Tunisia.
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DFT/B3LYP study of the solvent effect on the reaction enthalpies of homolytic and heterolytic OH bond cleavage in mono-substituted chromans. COMPUT THEOR CHEM 2011. [DOI: 10.1016/j.comptc.2011.09.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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20
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Gülçin İ. Antioxidant activity of food constituents: an overview. Arch Toxicol 2011; 86:345-91. [DOI: 10.1007/s00204-011-0774-2] [Citation(s) in RCA: 965] [Impact Index Per Article: 74.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 10/26/2011] [Indexed: 12/24/2022]
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21
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DFT/B3LYP study of the substituent effect on the reaction enthalpies of the individual steps of single electron transfer–proton transfer and sequential proton loss electron transfer mechanisms of chroman derivatives antioxidant action. COMPUT THEOR CHEM 2011. [DOI: 10.1016/j.comptc.2011.05.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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22
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La Porta FA, Ramalho TC, Santiago RT, Rocha MVJ, da Cunha EFF. Orbital signatures as a descriptor of regioselectivity and chemical reactivity: the role of the frontier orbitals on 1,3-dipolar cycloadditions. J Phys Chem A 2011; 115:824-33. [PMID: 21222451 DOI: 10.1021/jp108790w] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The FERMO concept emerges as a powerful and innovative implement to investigate the role of molecular orbitals applied to the description of breakage and formation of chemical bonds. In this work, Hartree-Fock (HF) theory and density functional (DFT) calculations were performed for a series of four reactions of 1,3-dipolar cycloadditions and were analyzed by molecular orbital (MO) energies, charge transfer, and molecular dynamics (ADMP) techniques for direct dynamics using the DFT method. The regioselectivity for a series of four 1,3-dipolar cycloaddition reactions was studied here using global and local reactivity indexes. We observed that the HOMO energies are insufficient to describe the behavior of these reactions when there is the presence of heteroatoms. By using the frontier effective-for-reaction molecular orbital (FERMO) concept, the reactions that are driven by HOMO, and those that are not, can be better explained, independent of the calculation method used, because both HF and Kohn-Sham methodologies lead to the same FERMO.
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Affiliation(s)
- Felipe A La Porta
- Department of Chemistry, Federal University of Lavras, Lavras, Minas Gerais, Brazil
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Guesmi NE, Boubaker T, Goumont R. Activation of the aromatic system by the SO2
CF3
group: Kinetics study and structure-reactivity relationships. INT J CHEM KINET 2010. [DOI: 10.1002/kin.20446] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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24
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Ramalho TC, Pereira DH. Understanding the substituent effect on the acidity of alcohols andpara-substituted phenols. MOLECULAR SIMULATION 2009. [DOI: 10.1080/08927020903015387] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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25
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El Guesmi N, Boubaker T, Goumont R, Terrier F. The Ambident Reactivity of 2,4,6-Tris(trifluoromethanesulfonyl)anisole in Methanol: Using the SO2CF3Group as a Tool to Reach the Superelectrophilic Dimension in σ-Complexation Processes. Chemistry 2009; 15:12018-29. [PMID: 19774563 DOI: 10.1002/chem.200901123] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Nizar El Guesmi
- Unité de Recherche de Chimie Théorique et Réactivité, Faculté des Sciences de Monastir, Avenue de l'Environnement, 5019 Monastir, Tunisia
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26
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Böhm S, Exner O. Interaction of two functional groups through the benzene ring: Theory and experiment. J Comput Chem 2009; 30:1069-74. [DOI: 10.1002/jcc.21131] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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27
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El Guesmi N, Boubaker T, Goumont R, Terrier F. Electrophilicity of aromatic triflones in σ-complexation processes. Org Biomol Chem 2008; 6:4041-52. [PMID: 18931813 DOI: 10.1039/b810273b] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Nizar El Guesmi
- Unité de Recherche de Chimie Théorique et Réactivité, Faculté des sciences de Monastir, Avenue de l'Environnement, 5019 Monastir, Tunisie
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Vianello R, Maksić ZB. Interpretation of Brønsted Acidity by Triadic Paradigm: A G3 Study of Mineral Acids. J Phys Chem A 2007; 111:11718-24. [DOI: 10.1021/jp0756606] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Robert Vianello
- Quantum Organic Chemistry Group, Division of Organic Chemistry and Biochemistry, Rudjer Bošković Institute, POB 180, 10002 Zagreb, Croatia, and Faculty of Science, University of Zagreb, Horvatovac 102A, 10000 Zagreb, Croatia
| | - Zvonimir B. Maksić
- Quantum Organic Chemistry Group, Division of Organic Chemistry and Biochemistry, Rudjer Bošković Institute, POB 180, 10002 Zagreb, Croatia, and Faculty of Science, University of Zagreb, Horvatovac 102A, 10000 Zagreb, Croatia
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Sadlej-Sosnowska N. Substituent active region – a gate for communication of substituent charge with the rest of a molecule: Monosubstituted benzenes. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.09.023] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Klein E, Lukes V. DFT/B3LYP study of the substituent effect on the reaction enthalpies of the individual steps of single electron transfer-proton transfer and sequential proton loss electron transfer mechanisms of phenols antioxidant action. J Phys Chem A 2007; 110:12312-20. [PMID: 17078630 DOI: 10.1021/jp063468i] [Citation(s) in RCA: 93] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The reaction enthalpies related to the individual steps of two phenolic antioxidants action mechanisms, single electron transfer-proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET), for 30 meta and para-substituted phenols (ArOH) were calculated using DFT/B3LYP method. These mechanisms represent the alternative ways to the extensively studied hydrogen atom transfer (HAT) mechanism. Except the comparison of calculated reaction enthalpies with available experimental and/or theoretical values, obtained enthalpies were correlated with Hammett constants. We have found that electron-donating substituents induce the rise in the enthalpy of proton dissociation (PDE) from ArOH+* radical cation (second step in SET-PT) and in the proton affinities of phenoxide ions ArO- (reaction enthalpy of the first step in SPLET). Electron-withdrawing groups cause the increase in the reaction enthalpies of the processes where electron is abstracted, i.e., in the ionization potentials of ArOH (first step in SET-PT) and in the enthalpy of electron transfer from ArO- (second step in SPLET). Found results indicate that all dependences of reaction enthalpies on Hammett constants of the substituents are linear. The calculations of liquid-phase reaction enthalpies for several para-substituted phenols indicate that found trends hold also in water, although substituent effects are weaker. From the thermodynamic point of view, entering SPLET mechanism represents the most probable process in water.
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Affiliation(s)
- Erik Klein
- Institute of Physical Chemistry and Chemical Physics, Slovak University of Technology, Radlinského 9, SK-812 37 Bratislava, Slovak Republic.
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Despotović I, Maksić ZB, Vianello R. Design of Brønsted Neutral Organic Bases and Superbases by Computational DFT Methods: Cyclic and Polycyclic Quinones and [3]Carbonylradialenes. European J Org Chem 2007. [DOI: 10.1002/ejoc.200700132] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Böhm S, Exner O. Inductive effects in radicals calculated from DFT energies; substituted bicyclo[2.2.2]octan-1-yloxy radicals. J Comput Chem 2007; 28:1783-9. [PMID: 17405123 DOI: 10.1002/jcc.20694] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Energies of a series of 4-substituted 1-oxybicyclo[2.2.2]octan-1-yloxy radicals with 18 various substituents were calculated within the framework of the DFT theory at the levels UB3LYP/6-311+G(d,p)//UB3LYP/6-311+G(d,p) and UB3LYP/6-311++G(2df,p)//UB3LYP/6-311+G(d,p) and compared with similar series of the parent alcohols, their deprotonated and protonated forms calculated at the levels B3LYP/6-311+G(d,p)//B3LYP/6-311+G(d,p) and B3LYP/6-311++G(2df,p)//B3LYP/6-311+G(d,p). The two levels are of the same performance and both are sufficient for molecules of this type according to comparison with scarce experimental gas-phase acidities and basicities. The substituent effects were analyzed in terms of isodesmic equations. In addition to strong dependence on the substituent inductive effect, a slight dependence on the electronegativity of the first atom of the substituent was proven in certain cases. In all aspects, there is no qualitative difference between the effects on radicals and on similar closed shell species. Radicals behave as slightly electron deficient; the substituent effect is weaker than that on the ions but stronger than on neutral molecules.
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Affiliation(s)
- Stanislav Böhm
- Department of Organic Chemistry, Prague Institute of Chemical Technology, 16628 Praha 6, Czech Republic
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DFT/B3LYP study of the substituent effect on the reaction enthalpies of the individual steps of sequential proton loss electron transfer mechanism of phenols antioxidant action: Correlation with phenolic CO bond length. ACTA ACUST UNITED AC 2007. [DOI: 10.1016/j.theochem.2006.11.002] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Maksić ZB, Vianello R. Physical origin of chemical phenomena: Interpretation of acidity, basicity, and hydride affinity by trichotomy paradigm. PURE APPL CHEM 2007. [DOI: 10.1351/pac200779061003] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Some of the most important aspects of modeling in chemistry are discussed in detail. It is argued that the interpretive side of (quantum) chemistry is indispensable, since it gives sense to a myriad of experimental and computational results. The usefulness of some physical modeling is illustrated by the trichotomy approach in rationalizing acidity, basicity, and hydride affinities of neutral organic compounds. According to trichotomy paradigm, the simple chemical reaction of protonation and H- attachment can be decomposed into three separate sequential steps, which in turn mirror the initial-, intermediate-, and final-state effects. Ample evidence is given, which convincingly shows that the trichotomy approach has some distinct advantages in interpreting aforementioned properties that belong to the most important ones in chemistry and biochemistry.
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Affiliation(s)
- Zvonimir B. Maksić
- 1Faculty of Science, The University of Zagreb, Horvatovac 102a, 10002 Zagreb, Croatia
| | - Robert Vianello
- 2Quantum Organic Chemistry Group, Division of Organic Chemistry and Biochemistry, Ruđer Bošković Institute, POB 180, 10002 Zagreb, Croatia
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Despotović I, Maksić ZB, Vianello R. Computational design of Brønsted neutral organic superbases—[3]iminoradialenes and quinonimines are important synthetic targets. NEW J CHEM 2007. [DOI: 10.1039/b611980h] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Vianello R, Peran N, Maksić ZB. Hydride Affinities of Substituted Alkenes: Their Prediction by Density Functional Calculations and Rationalisation by Triadic Formula. European J Org Chem 2007. [DOI: 10.1002/ejoc.200600640] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Vianello R, Peran N, Maksić ZB. Hydride Affinities of Some Substituted Alkynes: Prediction by DFT Calculations and Rationalization by Triadic Formula. J Phys Chem A 2006; 110:12870-81. [PMID: 17125303 DOI: 10.1021/jp064463o] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hydride affinities (HAs) of the ethynes substituted by a wide range of different substituents are considered by using the B3LYP methodology. The computed values are in fair agreement with available experimental data, which are unfortunately scarce. The trend of changes of the HAs is rationalized by trichotomy formula. One of the important results of this analysis is a finding that similar HA values might result from completely different effects. Alternative sites of the H- attack are examined and the difference in energies relative to the most susceptible positions is interpreted. Structural features of substituted ethyne hydrides are briefly discussed.
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Affiliation(s)
- Robert Vianello
- Quantum Organic Chemistry Group, Division of Organic Chemistry and Biochemistry, Ruder Bosković Institute, POB 180, 10002 Zagreb, Croatia.
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Maksić ZB, Vianello R. Comment on the Paper “On the Limits of Highest-Occupied Molecular Orbital Driven Reactions: The Frontier Effective-for-Reaction Molecular Orbital Concept”. J Phys Chem A 2006; 110:10651-2; discussion 10653-4. [PMID: 16956248 DOI: 10.1021/jp061030c] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Zvonimir B Maksić
- Quantum Organic Chemistry Group, Division of Organic Chemistry and Biochemistry, Ruder Bosković Institute, Bijenicka 54, 10000 Zagreb, Croatia.
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