New Insights in Chemical Reactivity by Means of Electron Pairing Analysis

Poater, Jordi; Solà, Miquel; Duran, Miquel; Fradera, Xavier

doi:10.1021/jp0204511

Cited by 59 publications

(94 citation statements)

References 31 publications

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“…The DIs of the covalent C-H bonds are somewhat smaller when correlation is included as expected from previous studies. 40,46 ELF Analysis. The ELF method represents an interesting alternative to AIM in order to analyze chemical bonding in molecules and solids.…”

Section: Resultsmentioning

confidence: 99%

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Bonding in Methylalkalimetals (CH₃M)_n(M = Li, Na, K;n= 1, 4). Agreement and Divergences between AIM and ELF Analyses

et al. 2006

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The chemical bonding in methylalkalimetals (CH 3 M) n (M ) Li-K; n ) 1, 4) has been investigated by making use of topological analyses grounded in the theory of atoms in molecules (AIM) and in the electron localization function (ELF). Both analyses describe the C-M bond as an ionic interaction. However, while AIM diagnoses a decrease of ionicity with tetramerization, ELF considers tetramers more ionic. Divergences emerge also when dealing with the bonding topology given by each technique. For the methylalkalimetal tetramers, the ELF analysis shows that each methyl carbon atom interacts through a bond pair with each of the three hydrogen atoms belonging to the same methyl group and through an ionic bond with the triangular face of the tetrahedral metal cluster in front of which the methyl group is located. On the other hand, the AIM topological description escapes from the traditional bonding schemes, presenting hypervalent carbon and alkalimetal atoms. Our results illustrate that fundamental concepts, such as that of the chemical bond, have a different, even colliding meaning in AIM and ELF theories.

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Section: Resultsmentioning

confidence: 99%

“…The accuracy of eqs 12 and 13 for computing LIs and DIs at the HF level has been discussed in a previous work. 40 Finally, using eqs 7-10 it can be proved that the following relations between LIs and DIs and variance, covariance, and average populations exist:…”

Section: Aim and Elf Topological Theoriesmentioning

confidence: 99%

Bonding in Methylalkalimetals (CH₃M)_n(M = Li, Na, K;n= 1, 4). Agreement and Divergences between AIM and ELF Analyses

et al. 2006

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“…[48] As a practical work around, one can derive an HF-like electron-pair density from the KS orbitals and calculate approximate localization and delocalization indexes at the DFT level using Equation (5). Because there is not yet a practical way to obtain molecular electron-pair densities in DFT methods, this is the only feasible approach at the moment for the calculation of approximate delocalization indexes at the DFT level.…”

Section: S Ij ðAþs Ij ðBþ ð5þmentioning

confidence: 99%

“…However, it has been shown that delocalization indexes evaluated within DFT provide useful chemical insight and constitute a suitable tool for the electronic characterization of molecules in different systems, including those with delocalized electrons in aromatic molecules. [49,35,48] …”

Section: S Ij ðAþs Ij ðBþ ð5þmentioning

confidence: 99%

Resonance Structures of the Amide Bond: The Advantages of Planarity

Mujika

Matxain

Eriksson

et al. 2006

Chemistry A European J

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Delocalization indexes based on magnitudes derived from electron-pair densities are demonstrated to be useful indicators of electron resonance in amides. These indexes, based on the integration of the two-electron density matrix over the atomic basins defined through the zero-flux condition, have been calculated for a series of amides at the B3LYP/6-31+G* level of theory. These quantities, which can be viewed as a measure of the sharing of electrons between atoms, behave in concordance with the traditional resonance model, even though they are integrated in Bader atomic basins. Thus, the use of these quantities overcomes contradictory results from analyses of atomic charges, yet keeps the theoretical appeal of using nonarbitrary atomic partitions and unambiguously defined functions such as densities and pair densities. Moreover, for a large data set consisting of 24 amides plus their corresponding rotational transition states, a linear relation was found between the rotational barrier for the amide and the delocalization index between the nitrogen and oxygen atoms, indicating that this parameter can be used as an ideal physical-chemical indicator of the electron resonance in amides.

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“…PDI and FLU have not been calculated at the MP2 level because it is computationally very demanding. Although it has been previously shown that the introduction of Coulomb correlation causes a major localization of the atomic basins, hence lower DIs [67,69,70], the DIs obtained from HF calculations yield the same qualitative trends than those derived from correlated wave functions. All calculations have been performed by means of the Gaussian03 [71] and AIMPAC [72] packages of programs.…”

Section: Methodsmentioning

confidence: 69%

Aromaticity changes along the reaction coordinate connecting the cyclobutadiene dimer to cubane and the benzene dimer to hexaprismane

2007

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Aromaticity and reactivity are two deeply connected concepts. Most of the thermally allowed cycloadditions take place through aromatic transition states, while transition states of thermally forbidden reactions are usually less aromatic, if at all. In this work, we perform a numerical experiment to discuss the change of aromaticity that occurs along the reaction paths that connect two antiaromatic units of cyclobutadiene to form cubane and two aromatic rings of benzene to yield hexaprismane. It is found that the aromaticity profile along the reaction coordinate of the [4+4] cycloaddition of two antiaromatic cyclobutadiene molecules goes through an aromatic highest energy point and finishes to an antiaromatic cubane species. Up to our knowledge, this represents the first example of a theoretically and thermally forbidden reaction path that goes through an intermediate aromatic region. In contrast, the aromaticity profile in the [6+6] cycloaddition of two aromatic benzene rings show a slow steady decrease of aromaticity from reactants to the highest energy point and from this to the final hexaprismane molecule a plunge of aromaticity is observed. In both systems, the main change of aromaticity occurs abruptly near the highest energy point, when the distance between the centers of the two rings is about 2.2 Å .

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New Insights in Chemical Reactivity by Means of Electron Pairing Analysis

Cited by 59 publications

References 31 publications

Bonding in Methylalkalimetals (CH₃M)_n(M = Li, Na, K;n= 1, 4). Agreement and Divergences between AIM and ELF Analyses

Bonding in Methylalkalimetals (CH₃M)_n(M = Li, Na, K;n= 1, 4). Agreement and Divergences between AIM and ELF Analyses

Resonance Structures of the Amide Bond: The Advantages of Planarity

Aromaticity changes along the reaction coordinate connecting the cyclobutadiene dimer to cubane and the benzene dimer to hexaprismane

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New Insights in Chemical Reactivity by Means of Electron Pairing Analysis

Cited by 59 publications

References 31 publications

Bonding in Methylalkalimetals (CH3M)n(M = Li, Na, K;n= 1, 4). Agreement and Divergences between AIM and ELF Analyses

Bonding in Methylalkalimetals (CH3M)n(M = Li, Na, K;n= 1, 4). Agreement and Divergences between AIM and ELF Analyses

Resonance Structures of the Amide Bond: The Advantages of Planarity

Aromaticity changes along the reaction coordinate connecting the cyclobutadiene dimer to cubane and the benzene dimer to hexaprismane

Contact Info

Product

Resources

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Bonding in Methylalkalimetals (CH₃M)_n(M = Li, Na, K;n= 1, 4). Agreement and Divergences between AIM and ELF Analyses

Bonding in Methylalkalimetals (CH₃M)_n(M = Li, Na, K;n= 1, 4). Agreement and Divergences between AIM and ELF Analyses