Parameters molecular orbital

It is difficult to treat the effect of a heteroatom on the localization energies of aromatic systems, but Brown has derived molecular orbital parameters from which he has shown that the rates of attack of the phenyl radical at the three positions of pyridine relatively to benzene agree within 10% with the experimental results. He and his co-workers have shown that the formation of 1-bromoisoquinoline on free-radical bromination of isoquinoline is in agreement with predictions from localization energies for physically reasonable values of the Coulomb parameters, but the observed orientation of the phcnylation of quinoline cannot be correlated with localization ener-... 

Recently, molecular orbital calculations on some iron complexes have been made by Gray and his co-workers (2, 30). These values for ferrous complexes are plotted in Figure 2 as the dashed line [3d 4s (MO)]. Hence, Mossbauer spectroscopy provides estimates for the 4s electron contribution for molecular orbital calculations. This correlation does not hold for high spin complexes such as FeCb" and FeFe ". Bersuker (3, 4) has attempted to relate both S and AEq directly to molecular orbital parameters. Using the equations developed from this approach, Bersuker, Gordanskii, and Makarov (5) have concluded that in tin tetrahalides the role of dx-Px bonding is significant. 

A variety of different approaches to the prediction of toxicity have been developed under the sponsorship of the Predictive Toxicology Evalnation project of the National Institnte of Environmental Health Sciences. The widespread application of compnta-tional techniqnes to stndies in biology, chemistry, and environmental sciences has led to a qnest for important, characteristic molecnlar parameters that may be directly derived from these compntational methods. Theoretical linear solvation energy relationships combine compntational molecular orbital parameters with the linear solvation energy relationship of Kamlet and Taft to characterize, nnderstand, and predict biological, chemical, and physical properties of chemical componnds (Eamini and Wilson, 1997). 

The use of molecular orbital parameters in this regard remain to be done, but may be of utility in drug design efforts. 

Mekenyan, O.G., Roberts, D.W., and Karcher, W., Molecular orbital parameters as predictors of skin sensitization of halo- and pseudohalobenzenes acting as SNAr electrophiles, Chem. Res. Toxicol., 10, 994-1000, 1997. 

Molecular orbital calculations show that electronic distributions at the positions a and p to nitrogen are similar to those at the corresponding positions of quinoxalines. Molecular orbital parameters obtained using CNDO functions a + n calculated electronic densities) are shown, and bond orders are given in Table 1. ... 

It has long been realized that excellent correlations exist between 1/2 or and molecular orbital parameters [172,178-181]. Correlations between voltammetric data and experimental observables such as ionization potentials (IP) [172,178,182,183], charge-transfer transition energies [172], and positions of p-bands in ultraviolet (UV) absorption spectra of the hydrocarbons [4,172] have been reported as well. The basis and limitations of such correlations have been examined critically [147,175,184]. For alkyl aromatic hydrocarbons (AAHs), the slope, a, of the correlation line [Eq. (56)], where E° is the standard potential for the reversible one-electron oxidation, is close to unity and has been used to suggest that in MeCN the solvation energies of the hydrocarbon radical cations are constant throughout the series [175]. 

Hall, L.H., Mohney, B. and Kier, L.B. (1993c). Comparison of Electrotopological Sate Indexes with Molecular Orbital Parameters Inhibition of MAO by Hydrazides. Quant.Struct.-Act. Relat., 12,44-48. 

Aptula, A.O., Roberts, D.W. and Cronin, M.T.D. (2005a) From experiment to theory molecular orbital parameters to interpret the skin sensitization potential of 5-chloro-2-methylisothiazol-3-one and 2-methylisothiazol-3-one. Chem. Res. Toxicol., 18, 324—329. 

Zhang L, Gao H, Hansch C, Selassie CD. Molecular orbital parameters and comparative QSAR in the analysis of phenol toxicity to leukemia cells. J Chem Soc Perkin Trans 1998 2 2553-2556. 

James McFarland (to William Purcell) There is an air of mysticism in the use of molecular orbital parameters. Do you feel that these parameters relate to biological processes that we are already familiar with or do they perhaps relate to something we don t yet understand about how drugs act If it is the former, would you elaborate on how we might interpret successful correlations with such terms as highest occupied molecular orbital, lowest unoccupied molecular orbital, and frontier orbital ... 

Electron density of electron pair in highest occupied molecular orbital. Parameters on = a+)S C-N exchange integral =... 

A Hiickel model similar to that used for dihydrodiazepines has been applied to benzodiazepines.42 A correlation was obtained between the longest-wavelength transition and the lowest unoccupied Hiickel molecular orbital parameter for benzo- and naphthodiazepines, which, it was suggested, indicated that these were n-ir transitions. 

In terms of the atomic orbital parameters the remaining molecular orbital parameters are... 

A second type of investigation can be typified by the work of Kooyman in the generation of arylmethyl and similarly delocalized radicals and the attempted correlation with calculated molecular orbital parameters ( ). Studies of this type represent but part of the overall subject of arylmethyl reactivity which includes not only radical generating hydrogen abstraction processes, Equation 1, but also the corresponding carbonium ion and... 

In an attempt to determine whether ground state molecular orbital parameters could correlate a relatively exothermic... 

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