Theoretical investigation on base-induced 1,2-eliminations in the model system fluoride ion + fluoroethane. The role of the base as a catalyst

Bickelhaupt, F. Matthias; Baerends, E. J.; Nibbering, N. M. M.; Ziegler, Tom

doi:10.1021/ja00073a035

Cited by 89 publications

(74 citation statements)

References 12 publications

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“…Although the stereochemistry, transition state, and energy profile for the E2 reactions have been well established by sophisticated experimental and theoretical investigations [16,17], the origin for acidity of the β-hydrogen is unclear, and interpretation on this matter is unavailable. The understanding of the β-hydrogen acidity in a functionalized substrate molecule such as a haloalkane is the key to study of the E2 reaction mechanism.…”

Section: Open Accessmentioning

confidence: 99%

“…They take place in the presence of a base [1,5,[16][17][18]. For chain-like haloalkanes, the E2 reaction requires a staggered conformation for the haloalkane substrate molecule, namely that the C α -X and C β -H bonds to be cleaved in the molecule must be anti-coplanar (Figure 4) [16][17][18].…”

Section: The E2 Reactions Of the Chain-like Haloalkanesmentioning

confidence: 99%

“…As a result, a haloalkane in an eclipsed conformation with the C α -X and C β -H bond syn-coplanar usually does not lead to an E2 reaction. The unfavorable effect of the eclipsed conformation on the E2 reaction has been accounted for previously as that the Pauli repulsion between lone pairs of electrons in the attacking base (B -) and the halogen -X atom enhances the energy of the transition state, making the syn-elimination process energetically difficult [16]. …”

Section: The E2 Reactions Of the Chain-like Haloalkanesmentioning

confidence: 99%

“…sophisticated mechanistic studies of the E2 reaction have been performed previously [16,17], prior to this work, no explanation on the origin of acidity for the β-H in functionalized organic compounds such as haloalkanes has been found. The author believes that understanding of the β-H acidity is the key to study of the E2 reactions.…”

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confidence: 99%

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Symmetry Analysis in Mechanistic Studies of Nucleophilic Substitution and β-Elimination Reactions

Sun

2010

Symmetry

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A mechanistic study of the bimolecular nucleophilic substitution (S N 2) reaction for halomethane CH 3 X (X = Cl, Br, or I) is approached by using symmetry principles and molecular orbital theory. The electrophilicity of the functionalized sp 3 -carbon is attributable to a 2p-orbital-based antibonding MO along the C-X bond. This antibonding MO, upon accepting an electron pair from a nucleophile, gives rise to dissociation of the C-X bond and formation of a new Nuc-C bond. Correlations are made between the molecular orbitals of reactants (Nuc -and CH 3 X) and products (NucCH 3 and X -). Similar symmetry analysis has been applied to mechanistic study of the bimolecular β-elimination (E2) reactions of haloalkanes. It well explains the necessity of an anti-coplanar arrangement of the C α -X and C β -H bonds for an E2 reaction (anti-elimination). Having this structural arrangement, the bonding C α -X (σC-X) and antibonding C β -H (σC-H * ) orbitals become symmetry-match. They can partially overlap resulting in increase in electron density in σC-H * , which weakens and polarizes the C β -H bond making the β-H acidic. An E2 reaction can readily take place in the presence of a base. The applications of symmetry analysis to the S N 2 and E2 reactions represent a new approach to studying organic mechanisms.

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Section: Open Accessmentioning

confidence: 99%

Section: The E2 Reactions Of the Chain-like Haloalkanesmentioning

confidence: 99%

Section: The E2 Reactions Of the Chain-like Haloalkanesmentioning

confidence: 99%

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confidence: 99%

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Symmetry Analysis in Mechanistic Studies of Nucleophilic Substitution and β-Elimination Reactions

Sun

2010

Symmetry

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“…The double-well feature for S N 2 reactions has been the subject of a great deal of research on the theoretical side by use of powerful computers coupled with modern techniques of molecular electronic structure. Recently gas-phase S N 2 reactions have been widely investigated by kinetic experiments [3][4][5], ab initio quantum and semiclassical dynamical methods and trajectory simulations [6,7], statistical mechanical studies [8,9], ab-initio and density functional structural analyses [10][11][12][13][14]. The importance of S N 2 studies in the chemical literature has made these reactions to constitute a paradigm for quantitative understandings of ion molecule reactions in general [15].…”

Section: Introductionmentioning

confidence: 99%

Concurrent Phenomena at the Reaction Path of the SN2 Reaction CH3Cl + F−. Information Planes and Statistical Complexity Analysis

Molina-Espíritu

Esquivel

Angulo

et al. 2013

Entropy

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An information-theoretical complexity analysis of the S N 2 exchange reaction for CH 3 Cl + F − is performed in both position and momentum spaces by means of the following composite functionals of the one-particle density: D-L and I-J planes and Fisher-Shannon's (FS) and López-Ruiz-Mancini-Calbet (LMC) shape complexities. It was found that all the chemical concepts traditionally assigned to elementary reactions such as the breaking/forming regions (B-B/F), the charge transfer/reorganization and the charge repulsion can be unraveled from the phenomenological analysis performed in this study through aspects of localizability, uniformity and disorder associated with the information-theoretical functionals. In contrast, no energy-based functionals can reveal the above mentioned chemical concepts. In addition, it is found that the TS critical point for this reaction does not show any chemical meaning (other than the barrier height) as compared with the concurrent processes revealed by the information-theoretical analysis. Instead, it is apparent from this study that a maximum delocalized state could be identified in the transition region which is associated to the charge transfer process as a new concurrent phenomenon associated with the charge transfer region (CT) for the ion-complex is identified. OPEN ACCESS Entropy 2013, 15 4085Finally it is discussed why most of the chemical features of interest (e.g., CT, B-B/F) are only revealed when some information-theoretic properties are taken into account, such as localizability, uniformity and disorder.

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Understanding reactivity with Kohn-Sham molecular orbital theory: E2-SN2 mechanistic spectrum and other concepts

1999

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Theoretical investigation on base-induced 1,2-eliminations in the model system fluoride ion + fluoroethane. The role of the base as a catalyst

Cited by 89 publications

References 12 publications

Symmetry Analysis in Mechanistic Studies of Nucleophilic Substitution and β-Elimination Reactions

Symmetry Analysis in Mechanistic Studies of Nucleophilic Substitution and β-Elimination Reactions

Concurrent Phenomena at the Reaction Path of the SN2 Reaction CH3Cl + F−. Information Planes and Statistical Complexity Analysis

Understanding reactivity with Kohn-Sham molecular orbital theory: E2-SN2 mechanistic spectrum and other concepts

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