Electrostatic and orbital interaction

Electrostatic and orbital interactions may steer reaction toward either carbon or oxygen. First, examine the electrostatic potential map for cyclohexanone lithium enolate. Which atom is more negatively charged, carbon or oxygen Is the difference significant If it is, what would be the favored mode of addition Does either methylation or silylation appear to be guided by electrostatics Explain. 

The EDA results of the parent compounds show, that all three components of AEjn, vary parallel with the total interaction energy. Due to the larger TM- -H2 distance in Mo(CO)sH2, both the repulsive Pauli interaction and the attractive electrostatic and orbital interactions are considerably weaker in this complex. The larger decrease in the attractive interactions as compared to that in the Pauli forces leads to ca. 3 kcal/mol destabilization with respect to Cr(CO)5H2 and W(CO)5H2. On the other hand, the ratio of the electrostatic and orbital interactions, and that of the components of is rather... 

Figure 2.43 H-bonding results from a balance of favorable electrostatics and orbital interactions. The stereoelectronic aspect is reflected in the preferred geometries when a large covalent aspect is present. Lone pairs that play a primary role in directionality are shown in blue, lone pairs that play a secondary role (i.e. for O-compounds) are in black. The second lone pair at S is not shown because it plays only a minor role (see Chapter 5 and ref. 75 fora more detailed discussion).

Multiple M=P bonding in (OC)5M=PR becomes evident with ADF s bond energy analysis in terms of electrostatic interactions, Pauli repulsion, and orbital interactions from which the a,Ti-separation is obtained using a symmetry decomposition scheme [21]. For singlet (OC)5Cr=PR, which has a BDEst of 40.5 kcal/mol, the a- and n-components are 62.4 and 40.9 kcal/mol, respectively. 

The semiconductor nanocrystallites work as electron acceptors from the photoexcited dye molecules, and the electron transfer as sensitization is influenced by electrostatic and chemical interactions between semiconductor surface and adsorbed dye molecules, e.g., correlation between oxidation potential of excited state of the adsorbed dye and potential of the conduction band level of the semiconductor, energetic and geometric overlapping integral between LUMO of dye molecule and the density of state distribution of the conduction band of semiconductor, and geometrical and molecular orbital change of the dye on the... 

The proposed approach to static cooperative Jahn-Teller effect is based on the exact effective Hamiltonian (7), acting in the reduced space of active one-centre distortions only. It involves effective force constants, which are analytically related to the parameters of the full microscopic Hamiltonian. Direct electronic interactions between sites, such as orbital-dependent electrostatic and exchange interactions [28], can be added to the effective Hamiltonian without modifying it. This approach proves to be especially efficient in the case of strong Jahn-Teller distortions, when the effects of second-order Jahn-Teller coupling become important. 

The balance of electrostatic and delocalization interactions in an isolated molecule may be perturbed by the influence of the solvent. In calculations based on Eq. 7, the analysis of solvation-energy terms suggested that the electrostatic contribution stabilizing the ap orientation of the acetal s ment is the conformationally dominant term. For example, in 2-methoxyoxane, the difference in energy of the (ap, ap) and (ap, sc) conformers in water, compared to that in the isolated molecule, caused by solute-solvent electrostatic interactions alone, amounts to 4 kJ.mor. Accordingly, the inter-and intra-molecular, electrostatic interactions operate in reverse directions in acetals. Whereas the intramolecular, electrostatic interactions are responsible, together with delocalization interactions, for the aiq)earance of the anomeric, reverse anomeric, and exo-anomeric effects, the solute-solvent electrostatic interactions lessen their im nitude, and may even cancel them. Of course, the solvent may also influence the electron distribution and energy of MO s in a molecule. In this way, the orbital interactions of lone-pairs and delocalization contributions to the anomeric effect may be scaled by the solvent, but this mechanism of the environmental effect is, in most cases, of only minor importance. 

The antiperiplanar arrangement of the carbanionic orbital and the o-acceptors in aromatic systems can be achieved by introducing endocyclic heteroatoms. The known hydride affinities for N-containing aromatics generally reflect the stabilizing effect of endocyclic o C-N orbitals (Figure ll ijfP- However, the situation is far from simple and cannot be readily explained by the combination of electrostatic and hyperconjugative interactions alone. A computational dissection of the complex interplay of multiple orbital interactions in these systems has not been undertaken so far but it is likely that the observed non-additivity of such effects reflects cooperativity and anticooperativity of stereoelectronic interactions. 

ADF calculates various chemically meaningful terms that add up to the bond energy, with an adaptation of Morokuma s bond-energy decomposition to the Kohn-Sham MO method. The individual terms are chemically intuitive quantities such as electrostatic energy, steric repulsion, Pauli repulsion, and orbital interactions. The latter are symmetry decomposed according to the Ziegler transition-state method. ... 

Olh cr I cacLiori s arc con trolled kin ctically, and the most stable product is not the major one observed. In these cases, you must look at the reactant side of the reaction coordinate to discover factors determ in in g th e ou tcorn e. Kloptn an an d Salem developed an analysis of reactivity in terms of two factois an electrostatic in leraclion approxim ated by atom ic ch arges an d a Kron tier orbital interaction, Fleming s book provides an excellent introduction to Ih ese ideas. 

The Born model is based on electrostatic interactions, dielectric permitivity, and orbital overlaps. It has the advantage of being fairly straightforward and adaptable to computational methods. The free energy for the polarization of the solute is expressed as... 

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