Resonance-energy calculations

It should be emphasized that the resonance energies calculated by the use of bond energies such as C = 0 from ketones do not include... 

Recently, Reinhoudt and Kouwenhoven 53) have reported, in connection with their successful synthesis of monocyclic thiepin 87, that the relatively high stability of 87 is attributed to the presence of the two methoxycarbonyl groups which cause a decrease in the electron density of the 8n-electron system. As a result, the formal anti-aromatic character is reduced. Traynelis and his coworkers 6) have also reported a slight increase in the thermal stability of benzo[6]thiepin when electron-withdrawing groups are present. These conclusions have subsequently been supported by resonance energy calculations on various thiepin derivatives59). Thus, the re-... 

On the other hand, to apply Dewar s approach within the QMRE scheme, it would be necessary to normalize resonance energies, calculated in terms of the above model, with respect to butadiene in accordance with... 

The variety of aromaticity indices based upon structural or magnetic molecular properties along with their values for pyrrole, the other five-membered heterocycles, benzene and cyclopentadiene are summarized in Table 31 in Section 3.01.5.2. Of these indices, the majority predict the aromaticity order benzene >thiophen>pyrrole >furan, in agreement with resonance energy calculations (Section 3.01.5.2). 

The value for resonance energy calculated using the bi-orthogonal dilated electron propagator is quite reasonable but the width of the 2II CO- using different decouplings is close only to that from the boomerang model. The... 

Alolecule Resonance energy calculated by method of a Experimental value of resonance energy kcals a = calc. kcals R -3 P Foala kcals... 

Several approximate methods for calculating resonance energies and widths for atom-diatom reactive collisions are discussed. In particular, we present resonance energy calculations by semlclassical and quantal vi-bratlonally adiabatic models based on minimum-energy and small-curvature paths, by the semlclassical SCF method, by quantal SCF and configuration-mixing... 

AhydH was measured in acetic acid. The authors give a short history of resonance energy calculations for azulene and arrive at their own crude (their adjective) estimate of 28 kcal mol 1. Azulene is aromatic because transfer of an electron pair from the seven-membered ring to the five-membered ring causes both rings to be aromatic. It is blue because of this electron transfer, which does not occur in its isomer naphthalene. 

Proton chemical shift data434 436 for 218, 219, and 220 or simple derivatives of these are consistent with the conclusions to be drawn from the Dewar resonance energy calculations. Thus proton 3 in 219434 absorbs at 5 6.70-6.79, which is at higher field than the proton absorptions reported for the other structures. 

Molecular orbital calculations for the (unknown) parent fully conjugated 1,3-diazocine (1) yielded a single solution, with C2v symmetry and delocalized bonding. (Analogous calculations for 1,4-diazocines afforded two solutions, and the solution was noted to depend upon choice of initial matrix elements.) Resonance energy calculations showed a decrease in antiaromaticity for this derivative relative to cyclooctatetraene <83Mi 922-03>. 

The delocalization or resonance energy DE of delocalized butadiene equals (4a + 4.4720p) - (4a + 4 ) = 0.4728. The resonance energy calculated in this way comes out in units... 

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