Pearson molecular similarity

In 2 computational aspects are discussed, with the assessment of DFT methods ( 2.1) in the evaluation of (a) ionization energies and electron affinities, and via eqn. (11), finite difference estimates of electronegativities and hardnesses ( 2.1.1) Mid (b) of dipole and quadrupole moments ( 2.1.2).In the final paragraph 2.2 a problem at the borderline between computational and conceptual DFT is tackled the evaluation of Fukui fimctions "beyond" the finite difference approximation. In 3 conceptual DFT is discussed, where in 3.1 attention is paid to the evaluation and/or use of DFT based concepts as such the shape factor and the local softness as Molecular Similarity indicators ( 3.1.1), and the nuclear Fukui function ( 3.1.2). In the final part of this Section ( 3.2) the role of DFT based concepts in various principles is discussed. The influence of solvent on the acidity of alkylalcohols is discussed within the framework of Sanderson s Electron ativity Equalization Principle [30] ( 3.2.1). The Hard and Soft Acids and Bases Principle and Pearson s Maximum Hardness Principle [31] are used as the guiding prindples in the study of the cycloaddition reactions of HNC to alkenes and aligmes. 

Parr, R. G. Pearson, R. G. J. Am. Chem. Soc. 1983, 105, 5, 7512. Mezey, P. G. Presented at Summer Course and Girona Seminar on Molecular Similarity, Girona, Catalonia, Spain. July 17-22, 1995. 

In crystals of DMPC (Pearson and Pascher, 1979) the lipids crystallize as stacked bilayers as in the crystals of DLPE, but with the hydrocarbon chains tilted by about 12° relative to the bilayer normal. The tilting of the hydrocarbon chains occurs because the phosphatidylcholine head groups require a larger surface area than that taken up by two hydrocarbon chains lying perpendicular to the bilayer surface. The cross-sectional area occupied by polar head-groups and hydrocarbon chains can be equal only when the hydrocarbon chains are tilted relative to the bilayer surface. This phenomenon is also observed in liquid crystals of DMPC in water. The molecular conformations of DLPE and DMPC are very similar both in the crystalline and liquid crystalline states (Hauser et al., 1981). The hydrocarbon chains of DLPE are not tilted in the crystal because the phosphatidylethanolamine head-groups do not occupy more than 40 on the surface of the crystalline bilayer. 

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