Generalization of an empirical model for bond dissociation energies

1993 ◽  
Vol 71 (4) ◽  
pp. 572-577 ◽  
Author(s):  
Yu-Ran Luo ◽  
Philip D. Pacey
Keyword(s):  
Experimental Data ◽  
Steric Effects ◽  
Bond Dissociation Energies ◽  
Average Deviation ◽  
Ring Strain ◽  
Methyl Substitution ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Alkyl Groups ◽  
Leaving Groups

A relationship between homolytic bond dissociation energies (BDEs) of C—X bonds and the electronegativity of X and the degree of methyl substitution of C has been extended. The range of leaving groups, X, now includes SiH3, GeH3, and PH2 and a variety of C-, N-, and O-centred radicals. Alkyl groups with ethyl and propyl chains attached to the radical centre have been incorporated. Steric effects, including those in bulky silanes, have been treated. The method is believed to be generally applicable where resonance and ring strain are not significant. BDEs for 73 bonds have been calculated; in the 42 cases where experimental data are available, the average deviation is 0.7 kcal/mol.

scholarly journals Web database on bond dissociation energies of organic compounds

2021 ◽  
Author(s):  
Vladimir Evgen'vich Tumanov ◽  
Andrei Ivanovich Prokhorov
Keyword(s):  
Experimental Data ◽  
Organic Compounds ◽  
Logical Structure ◽  
The Internet ◽  
Published Data ◽  
Bond Dissociation Energies ◽  
Web Database ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Wide Range

The article presents a scientific service on the Internet "Bond Dissociation Energies of Organic Compounds Database". This web database contains experimental values of dissociation energies of homolytic bonds. The service is intended for use by a wide range of chemists, theorists and practitioners in the open access on the Internet. The paper provides a brief overview of the literature sources of the dissociation energies of bonds of organic molecules, which are calculated theoretically, measured experimentally and estimated from kinetic and thermochemical experimental data. Descriptions of experimental data sources, classes of organic compounds and calculation methods are given. The logical structure of the database and the description of the main fields of its tables are given. The architecture of the web database is presented. The main search form of the database interface is presented and examples of search results for a specific organic compound and a fragment of a chemical formula are given. For most compounds, the values of the bond dissociation energy are given at a temperature of 298.15 K, which is usually absent in most sources (taking into account temperature correlations). Currently, work is underway to analyze the published data taking into account the entropy effects.

Charge distributions and chemical effects. XLIII. Bond dissociation energies and radical formation

1987 ◽  
Vol 65 (10) ◽  
pp. 2495-2503 ◽  
Author(s):  
Sándor Fliszár ◽  
Camilla Minichino
Keyword(s):  
Energy Difference ◽  
Approximation Formula ◽  
Bond Dissociation Energies ◽  
Charge Neutralization ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Alkyl Groups ◽  
Symmetric Molecule ◽  
New Energy ◽  
Molecular Ground State

The problem of bond dissociation, R1R2 → R1• + R2•, is addressed from the viewpoint that the fragments, R1 and R2, may not be individually electroneutral in the host molecule, whereas the corresponding radicals certainly are. The mutual charge neutralization of R1 by R2 during the cleavage of the bond linking R1 to R2 is described by an expression featuring only molecular ground-state properties. This expression translates directly into a new energy formula for the dissociation energy, D*(R1R2) = ε(R1R2) + CNE − E*nb + RE(R1) + RE(R2), where both the molecule and the radicals are taken at their potential minimum. The charge neutralization energy, CNE, profoundly affects the relationship between the dissociation (D*) and contributing bond energy (ε), i.e., the energy in the unperturbed molecule. Nonbonded interactions between R1 and R2, E*nb, are almost negligible. The reorganizational energy, RE, measures the energy difference between R• and the corresponding electroneutral group found in the symmetric molecule RR. Numerical applications to alkanes reveal an important cancellation of individual CNE terms accompanying the mutual charge neutralization of alkyl groups during the cleavage of CC bonds, i.e., [Formula: see text]. Theoretical εCC's lead to valid CC bond dissociation energies. In CH bond dissociations, on the other hand, the sum εCH + CNE remains nearly constant although individual εCH's may differ from one another by as much as 6 kcal mol−1. The appropriate approximation, [Formula: see text], shows in what manner charge neutralization energies disguise genuine contributing CH bond energies to create a perception of seemingly constant CH bond contributions.

scholarly journals Computational Study of Selected Amine and Lactam N-Oxides Including Comparisons of N-O Bond Dissociation Enthalpies with Those of Pyridine N-Oxides

Molecules ◽  
2020 ◽  
Vol 25 (16) ◽  
pp. 3703 ◽  
Author(s):  
Arthur Greenberg ◽  
Alexa R. Green ◽  
Joel F. Liebman
Keyword(s):  
Experimental Data ◽  
Bond Length ◽  
Computational Study ◽  
Enthalpy Of Vaporization ◽  
Enthalpy Of Sublimation ◽  
Bond Dissociation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Resonance Stabilization

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.

Oxidation of Alkylaromatic Hydrocarbons Over V2O5-Sb2O3/TiO2 Catalyst

1997 ◽  
Vol 62 (9) ◽  
pp. 1481-1490 ◽  
Author(s):  
Marcel Antol ◽  
Zuzana Cvengrošová ◽  
Imrich Vrábel ◽  
Ján Leško ◽  
Milan Hronec
Keyword(s):  
Experimental Data ◽  
Vapor Phase ◽  
Quantum Chemical ◽  
High Selectivity ◽  
Bond Dissociation Energies ◽  
Oxidative Dimerization ◽  
Dissociation Energies ◽  
Alkyl Groups ◽  
Substituted Toluenes ◽  
Ring Oxidation

Monoalkylbenzenes, polymethylbenzenes, para-substituted toluenes and monomethylnaphthalenes were oxidized in the vapor phase by oxygen-containing gas in the presence of water over a Sb2O3-promoted V2O5/TiO2 catalyst. This type of catalyst yields carboxylic acids with high selectivity. In the oxidation of substituted alkylbenzenes only alkyl groups were oxidized. No products of oxidative dimerization were detected. Only in the oxidation of methylnaphthalenes, also products of aromatic ring oxidation are formed. A correlation between experimental data and results of quantum-chemical calculations of bond dissociation energies is discussed.

scholarly journals Experimental bond dissociation energies of benzylpyridinium thermometer ions determined by threshold-CID and RRKM modeling

2017 ◽  
Vol 417 ◽  
pp. 69-75 ◽  
Author(s):  
David Gatineau ◽  
Antony Memboeuf ◽  
Anne Milet ◽  
Richard B. Cole ◽  
Héloïse Dossmann ◽  
...  
Keyword(s):  
Bond Dissociation Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Thermometer Ions
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