State correlation diagrams based

From the state correlation diagram based on Fig. 9 it can be seen that the triplet state of methylene and the ground state of ethylene correlate with... 

The photochemical disrotatory closure of butadiene to cyclobutene has been described with a state-correlation diagram, like that shown in Figure 21.4. It is based on the familiar orbital-correlation diagram of Woodward and Hoffmann," from which the intended correlations indicated by the dashed lines can readily be deduced. The solid lines indicate that there is an avoided crossing, which is put in as a result of the quantum mechanical noncrossing rule. It says that two states of the same total symmetry cannot cross. Instead, as they approach each other in energy, they will mix and separate, as the solid lines indicate. 

An alternative manner of building up the reaction profile for an SN2 reaction is based on the state correlation diagram (Shaik and Pross, 1982b Shaik, 1983, 1984). This approach is of theoretical interest since it provides further insight into the factors which govern barrier formation. 

The photochemical dimerization of unsaturated hydrocarbons such as olefins and aromatics, cycloaddition reactions including the addition of 02 ( A ) to form endoperoxides and photochemical Diels-Alders reaction can be rationalized by the Woodward-Hoffman Rule. The rule is based on the principle that the symmetry of the reactants must be conserved in the products. From the analysis of the orbital and state symmetries of the initial and final state, a state correlation diagram can be set up which immediately helps to make predictions regarding the feasibility of the reaction. If a reaction is not allowed by the rule for the conservation of symmetry, it may not occur even if thermodynamically allowed. 

BARRIER EXPRESSIONS BASED ON THE VALENCE BOND STATE CORRELATION DIAGRAM MODEL... 

On the basis of state correlation diagrams we may occasionally make predictions at variance with those based on orbital correlation diagrams, especially where radical species are involved. Consider the three atom electrocyclic process (34) with reference to Table 3 and Fig. 9. The most... 

Figure 4.13. Configuration correlation diagram (dotted lines) and the resulting state correlation diagram (solid and broken lines, respectively) for the disrotatory ring opening of cyclobutene, based on natural orbital correlations (by perihission from Bigot, 1980).

The leaving ligand treatment within the AOM has been extended" to the following steps of the photoisomerization process— the isomerization of the resulting five-coordinate species, followed by the nucleophilic attack of the entering ligand. The electronic structure control of the latter two steps was based on state correlation diagrams, but nicely translated into orbital pictures of the Woodward-Hoffman rules of conservation of orbital symmetry. 

FIGURE 2. State correlation diagram for H2O based on the energy eigenvalues of the 9 X 9 DIM model. 

BEP = Bell-Evans-Polanyi BOVB = breathing orbital VB FMVB = fragments in molecules based VB HL structure = Heitler-London structure PRS = perfectly resonating state VBCM = VB configuration mixing VBSCD = VB state correlation diagram VBSCF = self-consistent field VB. 

Model Equations for the Barrier and a Mechanism of Activation Based on the State Correlation Diagram... 

Fig. 14. Energy level and correlation diagram of the C2H5 photodissociation system in C8 and C v symmetry. Upper limits of the adiabatic energies of the A2A (3s) and B2A (Sp) states are based on absorption spectra. The crossing of the 2B2 and 2Ai states in Civ symmetry becomes an avoided intersection in Cs. The Biu state of C2H4 is reduced to B2 in C2v when the 2 axis is chosen to be perpendicular to the C2H4 plane. (From Amaral et al.39)...

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