Substituent effects on the benzylic bond dissociation enthalpy in benzyl bromides (C–Br) and tert-butylbenzenes (C–CH3): a gas phase thermolysis and liquid phase photoacoustic study

1997 ◽  
pp. 2307-2312 ◽  
Author(s):  
Lucas J. J. Laarhoven ◽  
Jan G. P. Born ◽  
Isabel W. C. E. Arends ◽  
Peter Mulder
Keyword(s):  
Liquid Phase ◽  
Gas Phase ◽  
Substituent Effects ◽  
Bond Dissociation Enthalpy ◽  
Bond Dissociation ◽  
Dissociation Enthalpy

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

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

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

Quinoxaline-1,4-dioxide: Substituent effects on the N–O bond dissociation enthalpy

2006 ◽  
Vol 429 (1-3) ◽  
pp. 18-22 ◽  
Author(s):  
José R.B. Gomes ◽  
Maria D.M.C. Ribeiro da Silva ◽  
Manuel A.V. Ribeiro da Silva
Keyword(s):  
Substituent Effects ◽  
Bond Dissociation Enthalpy ◽  
Bond Dissociation ◽  
Dissociation Enthalpy

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

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

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

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

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

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

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

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

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

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

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