Reorganization total

The stereochemistry of any pericyclic reaction can be predicted by counting the total number of electron pairs (bonds) involved in bond reorganization and then applying the mnemonic "The Electrons Circle Around. " That is, thermal (ground-slate) reactions involving an even number of electron pairs occur with either conrotatory or antarafacial stereochemistry. Exactly the opposite rules apply to photochemical (excited-state) reactions. 

The flat interface model employed by Marcus does not seem to be in agreement with the rough picture obtained from molecular dynamics simulations [19,21,64-66]. Benjamin examined the main assumptions of work terms [Eq. (19)] and the reorganization energy [Eq. (18)] by MD simulations of the water-DCE junction [8,19]. It was found that the electric field induced by both liquids underestimates the effect of water molecules and overestimates the effect of DCE molecules in the case of the continuum approach. However, the total field as a function of the charge of the reactants is consistent in both analyses. In conclusion, the continuum model remains as a good approximation despite the crude description of the liquid-liquid boundary. 

The individual terms, e , in Eq. (2.27) are termed one-electron orbital energies and correspond to the ionization potential (-e ) of an electron in MO i r assuming that no reorganization of the core nuclei, or the other (2N — 1) electrons, takes place during ionization. The total energy of the system [Eq. (2.27)] is clearly not the sum of the one-electron energies because electron-electron interaction terms are included twice. 

The total energy of reorganization of the outer sphere is obtained by integrating over the volume of the solution surrounding the reactant ... 

If in addition one inner-sphere mode of frequency oj, with Tuo 3> kT, is reorganized, the total rate constant can be written as a sum over partial rates ... 

The availability of cyclopentenones from butanolides allows the lactone annulation to facilitate the synthesis of cyclopentyl natural and unnatural products. An example that highlights the latter is dodecahedrane (178) for which 179 constitutes a critical synthetic intermediate 136,137). Lateral fusion of cyclopentenones as present in 179 can arise by acid induced reorganization and dehydration of 180. While a variety of routes can be envisioned to convert a ketone such as 182 into 180, none worked satisfactorily137 On the other hand, the cyclobutanone spiro-annulation approach via 181 proceeds in 64 % overall yield. Thus, the total carbon cource of dodecahedrane derives from two building blocks — cyclopentadiene and the cyclopropyl sulfonium ylide. 

In this equation, 2 is the total reorganization energy given by... 

Figure 1. Activation energy of electron-transfer process as a function of electronic energy gap of a reaction. Er = Eg + Ec is the total reorganization energy where Es is the classical solvent reorganization energy and Ec is the reorganization energy of an intramolecular mode, l

Figure 2. Deuterium isotope effect for electron transfer between ammine complexes as a function of the reduced electronic energy gap AE/EC where Er is the total reorganization energy E, = Eg + Ec. Key for parameters — —, hci)H/kBT — 2.0 and Es/Ec = 0 ------------------, Es/Ec = 1 and-------, Es/Ec = 2.

E = hv. In Figure 5 we show a plot of E vs total reorganization energy for various values of the electronic coupling. The... 

Figure 5. Mean band energy (E) vs. total reorganization energy [Eq. (18)]. The dashed curve is the equation, E = Et. The solid curves are calculated from an analytical expression (9). The solid dots are calculated from a diagonalization of the two-mode model secular determinant with c = —6.0, Ac, = 1.1, and vc, =...

Depending on the solvent polarity and redox potentials of a donor and an acceptor, the ions resulting from electron transfer may remain associated either as a contact IRP or as a solvent-separated IRP. In the contact pair, back electron transfer can take place. For such electron back-transfers, the solvent reorganization energy is less than 5% of the total reorganization energy (Serpa and Arnaut 2000). 

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