The Magnitude of Hyperconjugation in Ethane: A Perspective from Ab Initio Valence Bond Theory

Mo, Yirong; Wu, Wei; Song, Lingchun; Lin, Min; Zhang, Qianer; Gao, Jiali

doi:10.1002/ange.200352931

Cited by 52 publications

(27 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…All these effects are hyperconjugative interactions [34] of the target bonds with the wing bonds, and as such are much smaller than the D in-situ values due to the direct CÀC bonding. Thus, even though it is interesting to note that the higher propellanes have significant hyperconjugative interactions, of the inverted bond with the wing bonds, these energetic effects do not affect the conclusions in this paper, and are hence tabulated in the SI (Table S.6).…”

mentioning

confidence: 90%

An Excursion from Normal to Inverted CC Bonds Shows a Clear Demarcation between Covalent and Charge‐Shift CC Bonds

Shaik

Chen

et al. 2009

ChemPhysChem

Self Cite

View full text Add to dashboard Cite

What is the nature of the C-C bond? Valence bond and electron density computations of 16 C-C bonds show two families of bonds that flesh out as a phase diagram. One family, involving ethane, cyclopropane and so forth, is typified by covalent C-C bonding wherein covalent spin-pairing accounts for most of the bond energy. The second family includes the inverted bridgehead bonds of small propellanes, where the bond is neither covalent nor ionic, but owes its existence to the resonance stabilization between the respective structures; hence a charge-shift (CS) bond. The dual family also emerges from calculated and experimental electron density properties. Covalent C-C bonds are characterized by negative Laplacians of the density, whereas CS-bonds display small or positive Laplacians. The positive Laplacian defines a region suffering from neighbouring repulsive interactions, which is precisely the case in the inverted bonding region. Such regions are rich in kinetic energy, and indeed the energy-density analysis reveals that CS-bonds are richer in kinetic energy than the covalent C-C bonds. The large covalent-ionic resonance energy is precisely the mechanism that lowers the kinetic energy in the bonding region and restores equilibrium bonding. Thus, different degrees of repulsive strain create two bonding families of the same chemical bond made from a single atomic constituent. It is further shown that the idea of repulsive strain is portable and can predict the properties of propellanes of various sizes and different wing substituents. Experimentally (M. Messerschmidt, S. Scheins, L. Bruberth, M. Patzel, G. Szeimies, C. Paulman, P. Luger, Angew. Chem. 2005, 117, 3993-3997; Angew. Chem. Int. Ed. 2005, 44, 3925-3928), the C-C bond families are beautifully represented in [1.1.1]propellane, where the inverted C-C is a CS-bond, while the wings are made from covalent C-C bonds. What other manifestations can we expect from CS-bonds? Answers from experiment have the potential of recharting the mental map of chemical bonding.

show abstract

mentioning

confidence: 90%

An Excursion from Normal to Inverted CC Bonds Shows a Clear Demarcation between Covalent and Charge‐Shift CC Bonds

Shaik

Chen

et al. 2009

ChemPhysChem

Self Cite

View full text Add to dashboard Cite

show abstract

“…Pauli repulsion; Pauli repulsion = exchange ? repulsion; almost all of them contradict Bader et al's SCF assignment of less steric repulsion in S versus E. Valence bond analyses concluded that while S is favored by way of hyperconjugation, ''steric'' repulsion in E is responsible for 66 % [28] or more [29] of the barrier height. Su and Li [30], on the basis of a union of methyl radicals, assigned a cumulative D(exchange ?…”

Section: Ethane's Rotational Barriermentioning

confidence: 87%

The response electron–electron repulsion energy and energy component analysis in CC/MBPT methods

Salter

Wierzbicki

2016

Struct Chem

View full text Add to dashboard Cite

Molecular properties are computed as responses to perturbations (energy derivatives) in coupled-cluster (CC)/many-body perturbation theory (MBPT) models. Here, the CC/MBPT energy derivative with respect to a general two-electron (2-e) perturbation is assembled from gradient theory for 2-e property evaluation, including the electron repulsion energy. The correlation energy (DE) is shown to be the sum of response kinetic (DT), electronnuclear attraction (DV), and electron repulsion (DV ee ) energies. Thus, evaluation of total V ee for energy component analysis is simple: For total energy (E), total 1-e responses T and V, and nuclear-nuclear repulsion energy (V NN ), V ee = E -V NN -T -V is the true 2-e response value. Component energy analysis is illustrated in an assessment of steric repulsion in ethane's rotational barrier. Earlier SCF-based results (Bader et al. in J Am Chem Soc 112:6530, 1990) are corroborated: The higher-energy eclipsed geometry is favored versus staggered in the two repulsion energies (V NN and V ee ), while decisively disfavored in electron-nuclear attraction energy (V). Our best quality calculations (CCSD/cc-pVQZ) attain practical Virial Theorem compliance (i.e., agreement among the kinetic energy, potential energy, and total energy representations) in assigning 2.70 ± 0.06 to the barrier height; -195.80 kcal/mol is assigned to the drop in ''steric'' repulsion upon going to the eclipsed geometry. Steric repulsion is not responsible for any fraction of the *3 kcal/mol barrier.

show abstract

“…The geometry optimizations with these deletions were obtained at 6-31G(d) and 6-311G(3df,3pd) basis sets with Hartree−Fock method. 8,10 The potential energy surface (PES) scanning, varying R C2−H7 /θ and R C1−C2 /θ for the ionic ethanol (the angle θ made by the O−H bond with C−C− O plane, Figure 1), were calculated at the B3LYP/6-31G* level. The accurate dissociated energies of the two conformers were calculated with the M06-2X (at the 6-311++G(d,p) and 6-311+ +G(3d,p) basis sets) and MP2/aug-cc-pvdz methods.…”

Section: Methodsmentioning

confidence: 99%

Site-Selective Dissociation Processes of Cationic Ethanol Conformers: The Role of Hyperconjugation

Liu

et al. 2014

J. Phys. Chem. A

View full text Add to dashboard Cite

In present report, we explored hyperconjugation effects on the site- and bond-selective dissociation processes of cationic ethanol conformers by the use of theoretical methods (including configuration optimizations, natural bond orbital (NBO) analysis, and density of states (DOS) calculations, etc.) and the tunable synchrotron vacuum ultraviolet (SVUV) photoionization mass spectrometry. The dissociative mechanism of ethanol cations, in which hyperconjugative interactions and charge-transfer processes were involved, was proposed. The results reveal Cα-H and C-C bonds are selectively weakened, which arise as a result of the hyperconjugative interactions σCα-H → p in the trans-conformer and σC-C → p in gauche-conformer after being ionized. As a result, the selective bond cleavages would occur and different fragments were observed.

show abstract

The Magnitude of Hyperconjugation in Ethane: A Perspective from Ab Initio Valence Bond Theory

Cited by 52 publications

References 35 publications

An Excursion from Normal to Inverted CC Bonds Shows a Clear Demarcation between Covalent and Charge‐Shift CC Bonds

An Excursion from Normal to Inverted CC Bonds Shows a Clear Demarcation between Covalent and Charge‐Shift CC Bonds

The response electron–electron repulsion energy and energy component analysis in CC/MBPT methods

Site-Selective Dissociation Processes of Cationic Ethanol Conformers: The Role of Hyperconjugation

Contact Info

Product

Resources

About