MO and AD pictures

MO and AD pictures, 923 modeL minimal of a molecule, 489 mode, donating, 914 modes, normal, e58, el05... 

MO and AD pictures (p. 805) reaction stages (p. 806) role of states DA, D+A , D+A (p. 811) HOMO-LUMO crossing (p. 815) nucleophilic attack (p. 816) electrophilic attack (p. 818) cycloaddition reaction (p. 823) Woodward-Hoffmann rules (p. 825) Diels-Alder reaction (p. 825) diabatic and adiabatic potentials (p. 828) inverse Marcus region (p. 833) collective coordinate (p. 836) mean force potential (p. 836) Franck-Condon factors (p. 840) reorganization energy (p. 841)... 

An Electrostatic Preludium-The Maps of the Molecular Potential A Simple Model of Nucleophilic Substitution-MO, AD, and VB Formalisms MO Picture—> AD Picture Reaction Stages... 

The EH MO method is not in complete agreement with the rigid band picture of Ag-Pd alloys. It predicts that 0.3-0.4 electron per Ag atom is transferred from Ag to Pd when Ag atoms are added to random lattice positions of the 15-atom model. The number of d holes on bulk and surface Pd atoms in the cluster are shown as a function of composition in Fig. 14. Here bulk Pd atoms have more holes than do surface Pd atoms. The number of Pd d holes decreases with added Ag but does not equal zero at 60% Ag. 

Let s consider the shape of the MO first. The simplest picture considers molecular orbitals as resulting from the overlap of atomic orbitals. When atoms are separated by their usual bonding distance, their AOs overlap. Where this overlap occurs, either the electron waves reinforce and the electron density increases, or the electron waves cancel and the electron density decreases. The left-hand side of Figure 3.3 shows the overlap of the Is atomic orbitals on two different hydrogens (Hu and H/ ) when these hydrogens are separated by their normal bonding distance. The two atomic orbitals interact to produce two molecular orbitals. The MOs result from a linear combination of the AOs (called the LCAO approximation). Simply, this means that the AOs are either added (lsa + lsfc) or subtracted (1 sa — lst) to get the MOs. 

Then, a problem appeared how do you express one picture by another In particular, this has been important for expressing the MO picture in the AD one. More specifically, we are interested in calculating the contribution of an acceptor-donor structure in the Slater determinant written in the MO formalism, where the MOs are expressed by the donor ( ) and acceptor (x and x" ) orbitals in the following way ... 

The above theory is based on the acceptor/donor expansion functions (AD formalism). As has already been mentioned (p. 803), the third possibility (apart from AD and MO) is VB, in which the Slater determinants (playing the role of the expansion functions for o) are built of the atomic orbitals of the interacting species (Chapter 10, p. 520). How does such a VB picture look Let us consider a nucleophilic attack of the species X on the polarized double bond /C=Y, where Y represents an atom more electronegative than carbon (say, ojqfgen). Our goal is to expand the AD structures into the VB. The arguments of the kind already used for ethylene make it possible to limit ourselves exclusively to the frontier orbitals n, tt and TT (Fig. 14.18). 

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