Contributions of the structures as reaction proceeds

What therefore represents the ground-state wave function at the end of the reaction lb answer this question let us consider first all possible occupations of the three energy levels (corresponding to n, x, X ) four electrons. As before we assume for the orbital energy levels s . The number of such singlet-type 

let us ask what is the contribution of each of these structures in and 3d in the three stages of the reaction. This question is especially important for 1 0, because this Slater determinant is dominant for the ground-state wave function. The corresponding contributions in 2d and 34 are less important, because these configurations enter the ground-state Cl wave function multiplied by the tiny coefficients k. We have already calculated these contributions for the DA structure. The contributions of all the structures are given in Table 14.2. 

let us focus on which structures contribute to (because this determines 

Intermolecular Motion of Electrons and Nuclei Chemical Reactions 

Now we may think of going beyond the single determinant approximation by performing the Cl. In the R stage the DA structure dominates as before, but has some small admixtures of DA (because of 3 ) and D+ A (because of 2d) while at the product stage the contribution of the DA structure almost vanishes. Instead, some important contributions of the excited states appear, mainly of the 

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The implication of the multiple possible reaction pathways shown in Scheme 4.6 is that any computational approach must allow for the possible contribution of at least these three valence bond structures. " The simplest approach to the nature of the wavefunction for the Cope rearrangement is to just account for the correlation of the active orbitals of the reactants with those of the products. The o-bond between C3 and C4 of the reactant correlates to a(Ci-C ) in the product. Assuming that 1,5-hexadiene has C2 symmetry, both of these orbitals have a synunetry. The in-phase mixing of the two jc-bonds of the reactant (it(Cx-C2)-l-Jc(C5-Cg)) has b synunetry and correlates with (jc(C2-C3)-l-Jt(C4-C5)) of the product. The out-of-phase combination of the reactant Jc-bonds (it(Ci-C2) - it(C5-Cg)) has a synunetry and correlates with (jc(C2-C3) - Jc(C4-C5)) of the product. If the reaction proceeds through a C211 geometry, orbital symmetry demands that these active orbitals of must become Ug aJbJ. So, we may take as the aromatic ... 

Tomioka et al. reported the asymmetric Michael addition of lithium thiolates catalyzed by chiral aminoether 31 (Scheme 8D. 18) [39]. Thus, in the presence of catalytic amounts of 31 (10 mol %) and lithium 2-(trimethylsilyl)thiophenolate 32-Li (8 mol %), thiol 32 (3 equiv.) reacted with a,p-unsaturated esters at -78°C in toluene-hexane solvent to give the Michael adduct with up to 97% ee. In the ahsence of 31, the reaction of thiophenol proceeded in only 0.5% yield at room temperature. A monomeric complex consisting of 31 and lithium is proposed as the key reactive species in this asymmetric reaction. The trimethylsilyl group at the ortho-po-sition of the thiol moiety in 32 contributes to the formation of the stereochemically defined monomeric chelated structure, wherein the lithium cation is coordinated with the three heteroatoms of the tridentate ligand 31. The reactions of acyclic /nmv-a,P-unsaturated esters (R1 = Me, Et, Pr, Bu, Bu, PhCH9 R2 = H) proceeds with high enantioselectivity in... 

The reactant may be considered as a polarised carbonyl bond, reflected in contributions of covalent and ionic resonance structures. As the reaction proceeds, the contribution of both of these is replaced by the structure at the right of the diagram. Because of the greater concentration of positive charge on carbon in the reactant, donor substituents stabilise reactants more than transition state. In summary, donor substituents deactivate carbonyls. Cieplak acknowledged that the reactivity effect of a donor might be different from its stereochemical effect. 

The reaction process is considered to be the same for similar compounds, but the sensitivity of chemiluminescence has been suggested to be structure-dependent. The reactivity of a compound contributes to its sensitivity. Phenacylalcohol derivatives have been detected with different sensitivities in chemiluminescence analysis.In radical reactions, the reaction proceeds as follows in buffered solutions, a compound such as phenacylalcohol is easily attacked by oxidation if traces of a copper or iron salt are present, and the superoxide reacts with luminol or lueigenin to produce chemiluminescence as shown in Figure 11.7. 

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