CH bond dissociation energies, isolated stretching frequencies, and radical stabilization energy

McKean, D.C.

doi:10.1002/kin.550210608

Cited by 47 publications

(18 citation statements)

References 69 publications

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“…Thus we believe that our value is more accurate than the previous ones. The r (C-H) bond length may be estimated independently from the isolated stretching frequency (56), whose value is 2931 cm −1 (57). It gives r (C−H) = 1.091(2)Å, in fair agreement with our ab initio value.…”

Section: Ab Initio Calculationssupporting

confidence: 60%

“…It gives r (C−H) = 1.091(2)Å, in fair agreement with our ab initio value. The small difference may easily be explained by the fact that this vibrational frequency was only approximately corrected for a strong Fermi resonance (57). The structure of glyoxylic acid was calculated in the same way, but the expensive calculation at the CCSD(T)/cc-pVQZ level was replaced, as discussed above, by simpler calculations using the following approximation formula: CCSD(T)/cc-pVQZ ≈ CCSD(T)/cc-pVTZ + MP2/cc-pVQZ-MP2/cc-pVTZ.…”

Section: Ab Initio Calculationsmentioning

confidence: 95%

See 1 more Smart Citation

The Submillimeter-Wave Spectrum and Quantum Chemical Calculations of Glyoxylic Acid

Bakri¹,

Demaison²,

Margulès³

et al. 2001

Journal of Molecular Spectroscopy

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Section: Ab Initio Calculationssupporting

confidence: 60%

Section: Ab Initio Calculationsmentioning

confidence: 95%

The Submillimeter-Wave Spectrum and Quantum Chemical Calculations of Glyoxylic Acid

Bakri¹,

Demaison²,

Margulès³

et al. 2001

Journal of Molecular Spectroscopy

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“…For example, the CH stretching modes undergo Fermi resonances with the first overtone of the CH 3 and CH 2 bending modes (both CCH and HCH bending). This leads to a shift in the CH stretching frequency that makes the determination of a localized CH stretching frequency rather uncertain [41,[89][90][91][92][93][94].…”

Section: Local Mode Properties Obtained From Experimentsmentioning

confidence: 99%

Generalization of the Badger Rule Based on the Use of Adiabatic Vibrational Modes

Kraka

Larsson

Cremer

2010

Computational Spectroscopy

115

150

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Empirical relationships relating bond lengths to the corresponding bond stretching frequencies or bond stretching force constants were first derived in 1920s (see Table 4.1 for a summary) and have ever since been a topic of research on the nature of the chemical bond . It is remarkable that in a time of easily accessible quantum chemical results, there remains a need for empirically based estimates of either bond lengths or stretching frequencies. There are three primary reasons why such empirical rules and relationships are still valuable tools for modern research:(1) Established relationships between bond properties add to our understanding of the chemical bond, especially if they can be rationalized on a quantum mechanical basis because bonding between atoms is a quantum mechanical phenomenon.(2) There are experimental situations in which it is relatively easy to measure one bond property but difficult to obtain other bond properties. For example, it is easier to measure the vibrational spectra of a compound than to carry out a structural analysis. This is especially true for solid materials that do not crystallize, molecules on a surface, or molecules in some form of aggregation. If quantum chemical calculations are feasible only for model systems rather than the actual targets of chemical research, then vibrational spectroscopy may be the only tool for obtaining information that provides an insight into bond properties. (3) In the realm of computational chemistry, there is also a need for empirical relationships. They may be used to determine suitable bonding force fields for molecular mechanics utilizing force constant -bond length relationships. For quantum chemical geometry optimization, there is the need to set up a guess matrix of energy second derivatives (the Hessian matrix corresponding to the force constant matrix of a molecule), which is best done with the help of available geometry information and a suitable force constant -bond length relationship. For example, the standard procedure to calculate the geometry of a molecule is based on an initial guess of the energy Hessian derived with the help of the Badger rule [42,55]. It is due to these three reasons that there is ongoing research exploring the relationships between bond length r, bond stretching Computational Spectroscopy: Methods, Experiments and Applications. Edited by J€ org Grunenberg

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“…In the mid-1970s McKean [55,56] introduced what he called isolated CH stretching frequencies. By deuterium substitution of all H atoms of a CH 3 or CH 2 group but one, he could measure CH stretching frequencies that were only a little contaminated by coupling with other modes or Fermi resonances.…”

mentioning

confidence: 99%

Characterization of CF Bonds with Multiple‐Bond Character: Bond Lengths, Stretching Force Constants, and Bond Dissociation Energies

Kraka

2009

ChemPhysChem

105

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Isoelectronic C=F(+) and C=O bonds contained in fluoro-substituted carbenium ions, aldehydes, and ketones are investigated with regard to their bond properties by utilizing the vibrational spectra of these molecules. It is demonstrated that bond dissociation energies (BDEs), bond lengths, vibrational stretching frequencies, and bond densities are not reliable descriptors of the bond strength. The latter is related to the intrinsic BDE, which corresponds to nonrelaxed dissociation products retaining the electronic structure and geometry they have in the molecule. It is shown that the harmonic stretching force constants k(a) of the localized internal coordinate vibrations (adiabatic vibrational modes) reflect trends in the intrinsic BDEs. The k(a) values of both CO and CF bonds are related to the bond lengths through a single exponential function. This observation is used to derive a common bond order n for 46 CO- and CF-containing molecules that reliably describes differences in bonding. CF bonds in fluorinated carbenium ions possess bond orders between 1.3 and 1.7 as a result of significant pi back-bonding from F to C, which is sensitive to electronic effects caused by substituents at the carbenium center. Therefore, the strength of the C=F(+) bond can be used as a sensor for (hyper)conjugation and other electronic effects influencing the stability of the carbenium ion. The diatomic C=F(+) ion has a true double bond due to pi donation from the F atom. The characterization of CF bonds with the help of adiabatic stretching modes is also applied to fluoronium ions (n = 0.3-0.6) and transition states involving CF cleavage and HF elimination (n = 0.7-0.8).

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CH bond dissociation energies, isolated stretching frequencies, and radical stabilization energy

Cited by 47 publications

References 69 publications

The Submillimeter-Wave Spectrum and Quantum Chemical Calculations of Glyoxylic Acid

The Submillimeter-Wave Spectrum and Quantum Chemical Calculations of Glyoxylic Acid

Generalization of the Badger Rule Based on the Use of Adiabatic Vibrational Modes

Characterization of CF Bonds with Multiple‐Bond Character: Bond Lengths, Stretching Force Constants, and Bond Dissociation Energies

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