Electronegativity, equalization

Sanderson, Chemical Bonds and Bond Energies, Academic Press, New York, 1976 R. T. Sanderson, Polar Covalence, Academic Press, New York, 1983. 

This approach was extended by M. Sastry to a variety of organic compounds. For example, the charges calculated for the carbon atoms in CFjCOjCjH are as shown below. We see that the carbon of the methyl group carries a small negative charge, whereas the carbons bound to more electronegative elements are positive. 

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Molecule Atom Equation 1-1 Inclusion of doublebond character Electronegativity equalization... 

Bratsch, S.G. Electronegativity Equalization with Pauling Units J. Chem. Educ. 1984, 61, 588-589. 

Sorich MJ, McKinnon RA, Miners JO, Winkler DA, Smith PA. Rapid prediction of chemical metabolism by human UDP-glucuronosyltransferase isoforms using quantum chemical descriptors derived with the electronegativity equalization method. J Med Chem 2004 47 5311-7. 

Nalewajski RF (1991) Normal (decoupled) representation of electronegativity equalization equations in a molecule. Int J Quant Chem 40(2) 265—285... 

Nalewajski RF (1998) On the chemical potential/electronegativity equalization in density functional theory. Polish J Chem 72(7) 1763-1778... 

Toufar H, Baekelandt BG, Janssens GOA, Mortier WJ, Schoonheydt RA (1995) Investigation of supramolecular systems by a combination of the electronegativity equalization method and a Monte-Carlo simulation technique. J Phys Chem 99(38) 13876—13885... 

Yang ZZ, Wang CS (1997) Atom-bond electronegativity equalization method. 1. Calculation of the charge distribution in large molecules. J Phys Chem A 101(35) 6315-6321... 

Wang CS, Li SM, Yang ZZ (1998) Calculation of molecular energies by atom-bond electronegativity equalization method. Theochem J Mol Struct 430, 191-199... 

Wang CS, Yang ZZ (1999) Atom-bond electronegativity equalization method. II. Lone-pair electron model. J Chem Phys 110(13) 6189-6197... 

Cong Y, Yang ZZ (2000) General atom-bond electronegativity equalization method and its application in prediction of charge distributions in polypeptide. Chem Phys Lett 316(3-4) 324-329... 

Yang ZZ, Wang CS (2003) Atom-bond electronegativity equalization method and its applications based on density functional theory. J Theor Comput Chem 2(2) 273-299... 

Yang ZZ, Wu Y, Zhao DX (2004) Atom-bond electronegativity equalization method fused into molecular mechanics. I. A seven-site fluctuating charge and flexible body water potential function for water clusters. J Chem Phys 120(6) 2541-2557... 

That is, the Milliken electronegativity equals the slope of the U versus N curve. The apos-trophes refer to the fact that it is a pseudo-curve since it is only dehned for integral num-bers of electrons. 

A chemical bond exhibiting 100% covalent character and 0% ionic character occurs between identical nonmetals atoms in which the difference in electronegativity (AEN) is zero. An example is the H-H bond. There are atoms with essentially the same electronegativity, e.g. N and Cl both have an electronegativity equal to 3.0 to 2 significant figures, so the N-Cl bond would exhibit close to 100% covalent character and 0% ionic character . 

As already mentioned, through DFT, it has been possible to explain the electronegativity equalization principle [1,7,10-13] and the hard and soft acids and bases principle [12,15-22] and, additionally, it has also been possible to introduce new ones like the maximum hardness principle [52,53] and the local hard and soft acids and bases principle [20,54—56]. 

These descriptors have been widely used for the past 25 years to study chemical reactivity, i.e., the propensity of atoms, molecules, surfaces to interact with one or more reaction partners with formation or rupture of one or more covalent bonds. Kinetic and/or thermodynamic aspects, depending on the (not always obvious and even not univoque) choice of the descriptors were hereby considered. In these studies, the reactivity descriptors were used as such or within the context of some principles of which Sanderson s electronegativity equalization principle [16], Pearson s hard and soft acids and bases (HSAB) principle [17], and the maximum hardness principle [17,18] are the three best known and popular examples. 

As a further step currently under investigation, the relationship between local polarizability and local softness is studied with the aim to substitute atom-in-molecule polarizabilities by atom-condensed softness values. In this way, conceptual DFT could be exploited in a computational strategy, an ansatz rarely used until now, the best known example being the electronegativity equalization method [101]. 

Nalewajski, R. F. and O. Sikora. 2000. Electron-following mapping transformations from the electronegativity equalization principle. J. Phys. Chem. A 104 5638-5646. 

Heidler, R., janssens, G.O.A., Mortier, W.J., and Schoonheydt, R.A. (1995) Charge sensitivity analysis of intrinsic basicity of faujasite-type zeolites using the electronegativity equalization method... 

The crudest one is Sanderson s electronegativity equalization principle [39, 40] according to which atoms-in-molecule make electron transfers from lower to higher electronegative parts thus achieving equilibrium in electronegativity. 

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