Electron reorganization

The transition state for the first step of the Claisen rearrangement bears much m common with the transition state for the Diels-Alder cycloaddition Both involve a con certed six electron reorganization... 

Section 24 13 On being heated allyl aryl ethers undergo a Claisen rearrangement to form o allylphenols A cyclohexadienone formed by a concerted six tt electron reorganization is an intermediate... 

Electron reorganization. The orbitals in are not quite the same as in M because there... 

The great advantage of sueh HF-Xa calculations over traditional HF ones is that they take account of electron reorganization on ionization, and so the Xa ionization energies were thought to be superior. 

In many cases, however, the ortho isomer is the predominant product, and it is the meta para ratio which is close to the statistical value, in reactions both on benzenoid compounds and on pyri-dine. " There has been no satisfactory explanation of this feature of the reaction. One theory, which lacks verification, is that the radical first forms a complex with the aromatic compound at the position of greatest electron density that this is invariably cither the substituent or the position ortho to the substituent, depending on whether the substituent is electron-attracting or -releasing and that when the preliminary complex collapses to the tr-complex, the new bond is most likely to be formed at the ortho position.For heterocyclic compounds such as pyridine it is possible that the phenyl radical complexes with the nitrogen atom and that a simple electronic reorganization forms the tj-complex at the 2-position. 

Sanchez, A. J. Konopelski, J. P. Phenol benzylic epoxide to quinone methide electron reorganization synthesis of ( )-taxodone. J. Org. Chem. 1994, 59, 5445-5452. 

These products are thought to arise by electron transfer to the nitrogen atom followed by proton transfer and electron reorganization/1085... 

The contrary view of ionization developed in Section 3.2.4 is that strong electronic reorganization of the cation negates the basic assumption of Koopmans theorem. Superficial aspects of the Koopmans picture are preserved, however, because... 

Stemheimer electric field shielding tensors (26), electronic reorganization terms in vibrational force constants (28, 29 softness kernels (30, 31 ... 

Mechanistically, analogous to what already is suggested for 5-azido- or S-diazomethyl-1,2,3-triazoles (Section II,C), the participation of open-chain intermediates 287 or 288 is proposed (Scheme 46) the subsequent hetrocyclization engaging the pivotal sulfur and the azido or diazo-methyl side-chain develops into the rearranged 285 or 290, respectively. On the other hand, a concerted electronic reorganization involving the side-chain... 

The polarization potential provides the energy due to electronic reorganization of the molecule as a result of its interaction with a point positive charge. The sum of the electrostatic and polarization potentials provides a better account of the energy of interaction of a point positive charge than available from the electrostatic potential alone. It properly orders the proton affinities of trimethylamine, dimethyl ether and fluoromethane. 

While the possibility of a very rapid electron reorganization from a low energy triplet state is ruled out by the observed insensitivity of the photo-Fries rearrangement to paramagnetic quenchers (vide supra) and the usual rate of intersystem crossing (kST = 10s—1011 sec-1 43a), the remaining alternative to singlet processes for both Path A and Path B, i.e., reactions from... 

The proposed mechanism agrees with the general picture presented in Eqs. (5) and (6). The electronic reorganization of the adduct allows the release of N20 and NH3, with [Fen(CN)5H20]3- formation [Eq. (11)]. Strong evidence for the mechanism was obtained by using 15N in NP, with the result that the label appeared only in N15NO, as measured by mass spectrometry, but not in NH3 or in the amines. 

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