Modern Valence Bond Theory

Cooper, David L.; Gerratt, Joseph; Raimondi, Mario

doi:10.1002/9780470142943.ch6

Cited by 156 publications

(66 citation statements)

References 156 publications

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“…Based on previous considerations, [45,46] the quantity B would be related to the singlet-to-triplet excitation (DE ST ) of the CH 3 ÀX bond in the transition states geometry by Equation (23), and thus Equation (24).…”

Section: Discussionmentioning

confidence: 99%

Identity S_N2 Reactions X⁻+CH₃X→XCH₃+X⁻ (X=F, Cl, Br, and I) in Vacuum and in Aqueous Solution: A Valence Bond Study

Song

Hiberty

et al. 2006

Chemistry A European J

103

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The recently developed (L. Song, W. Wu, Q. Zhang, S. Shaik, J. Phys. Chem. A 2004, 108, 6017) valence bond method coupled with a polarized continuum model (VBPCM) has been applied to the identity SN2 reaction of halides in the gas phase and in aqueous solution. The barriers computed at the level of the breathing orbital VB method (P. C. Hiberty, J. P. Flament, E. Noizet, Chem. Phys. Lett. 1992, 189, 259), BOVB and VBPCM//BOVB, are comparable to CCSD(T) and CCSD(T)//PCM results and to experimentally derived barriers in solution (W. J. Albery, M. M. Kreevoy, Adv. Phys. Org. Chem. 1978, 16, 85). The reactivity parameters needed to apply the valence bond state correlation diagram (VBSCD) method (S. Shaik, J. Am. Chem. Soc. 1984, 106, 1227), were also determined by VB calculations. It has been shown that the reactivity parameters along with their semiempirical derivations provide a satisfactory qualitative and quantitative account of the barriers.

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Section: Discussionmentioning

confidence: 99%

Identity S_N2 Reactions X⁻+CH₃X→XCH₃+X⁻ (X=F, Cl, Br, and I) in Vacuum and in Aqueous Solution: A Valence Bond Study

Song

Hiberty

et al. 2006

Chemistry A European J

103

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“…The VB wavefunction Φ for the S N 2 reaction between hydrosulfide ion and chloromethane is written as a linear combination of the six configurations depicted in Scheme 1:13,14,47…”

Section: Methodsmentioning

confidence: 99%

An Effective Hamiltonian Molecular Orbital-Valence Bond (MOVB) Approach for Chemical Reactions as Applied to the Nucleophilic Substitution Reaction of Hydrosulfide Ion and Chloromethane

Song

Gao

2008

J. Chem. Theory Comput.

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An effective Hamiltonian mixed molecular orbital and valence bond (EH-MOVB) method is described to obtain an accurate potential energy surface for chemical reactions. Building upon previous results on the construction of diabatic and adiabatic potential surfaces using ab initio MOVB theory, we introduce a diabatic-coupling scaling factor to uniformly scale the ab initio off-diagonal matrix element H12 such that the computed energy of reaction from the EH-MOVB method is in agreement with the target value. The scaling factor is very close to unity, resulting in minimal alteration of the potential energy surface of the original MOVB model. Furthermore, the relative energy between the reactant and product diabatic states in the EH-MOVB method can be improved to match the experimental energy of reaction. A key ingredient in the EH-MOVB theory is that the off-diagonal matrix elements are functions of all degrees of freedom of the system and the overlap matrix is explicitly evaluated. The EH-MOVB method has been applied to the nucleophilic substitution reaction between hydrosulfide and chloromethane to illustrate the methodology and the results were matched to reproduce the results from ab initio valence bond self-consistent valence bond (VBSCF) calculations. The diabatic coupling (the off-diagonal matrix element in the generalized secular equation) has small variations along the minimum energy reaction path in the EH-MOVB model, whereas it shows a maximum value at the transition state and has nearly zero values in the regions of the ion-dipole complexes from VBSCF calculations. The difference in the diabatic coupling stabilization is attributed to the large overlap integral in the computationally efficient MOVB method.

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“…The Spin-Coupled (SC) method, developed by Gerratt and coworkers, [38][39][40][41][42][43] differs from the GVB-SOPP method in the sense that it removes the orthogonality and perfect-pairing restrictions. The method still relies on a single-configuration type, but all the modes of spin-pairing are included in the wave functions and the orbitals are allowed to overlap freely with each other.…”

Section: The Spin-coupled Valence Bond Methodsmentioning

confidence: 99%

A survey of recent developments in ab initio valence bond theory

Hiberty

Shaik

2006

J Comput Chem

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Starting from the 1980s and onwards, Valence Bond theory has been enjoying renaissance that is characterized by the development of a growing number of ab initio methods, and by many applications to chemical reactivity and to the central paradigms of chemistry. Owing the increase of computational power of modern computers and to significant advances in the methodology, valence bond theory begins to offer a sound and attractive alternative to Molecular Orbital theory. This review aims at summarizing the most important developments of ab initio valence bond methods during the last two or three decades, and is primarily devoted to a description of what the various methods can actually achieve within their specific scopes and limitations. Key available softwares are surveyed.

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Modern Valence Bond Theory

Cited by 156 publications

References 156 publications

Identity S_N2 Reactions X⁻+CH₃X→XCH₃+X⁻ (X=F, Cl, Br, and I) in Vacuum and in Aqueous Solution: A Valence Bond Study

Identity S_N2 Reactions X⁻+CH₃X→XCH₃+X⁻ (X=F, Cl, Br, and I) in Vacuum and in Aqueous Solution: A Valence Bond Study

An Effective Hamiltonian Molecular Orbital-Valence Bond (MOVB) Approach for Chemical Reactions as Applied to the Nucleophilic Substitution Reaction of Hydrosulfide Ion and Chloromethane

A survey of recent developments in ab initio valence bond theory

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Modern Valence Bond Theory

Cited by 156 publications

References 156 publications

Identity SN2 Reactions X−+CH3X→XCH3+X− (X=F, Cl, Br, and I) in Vacuum and in Aqueous Solution: A Valence Bond Study

Identity SN2 Reactions X−+CH3X→XCH3+X− (X=F, Cl, Br, and I) in Vacuum and in Aqueous Solution: A Valence Bond Study

An Effective Hamiltonian Molecular Orbital-Valence Bond (MOVB) Approach for Chemical Reactions as Applied to the Nucleophilic Substitution Reaction of Hydrosulfide Ion and Chloromethane

A survey of recent developments in ab initio valence bond theory

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Product

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Identity S_N2 Reactions X⁻+CH₃X→XCH₃+X⁻ (X=F, Cl, Br, and I) in Vacuum and in Aqueous Solution: A Valence Bond Study

Identity S_N2 Reactions X⁻+CH₃X→XCH₃+X⁻ (X=F, Cl, Br, and I) in Vacuum and in Aqueous Solution: A Valence Bond Study