Electrostatic potentials chemical applications

The electrostatic potential V r) that is created in the space around a molecule by its nuclei and electrons is a well-established guide to chemical reactivity and molecular interactive behavior. Unlike many of the other quantities used now and earlier as indices of reactivity, e.g., atomic charges, the electrostatic potential is a real physical property, one that can be determined experimentally by diffraction methods as well as computationally. However, V r) is most commonly obtained computationally. With the recent advances in computer technology, it is currently being applied to a variety of significant chemical systems. 

The molecular electrostatic potential V (r) is defined rigorously by equation (1), in terms of the electronic density p r) and the charges and positions of the nuclei, which are assumed to be fixed in space. 

Za is the charge on nucleus A, located at Ra- The two terms on the right side of equation (1) reflect the contributions of the nuclei and electrons, respectively the former is positive in sign, the latter negative. The sign of V r) in any particular region of space consequently depends upon which of these terms is dominant there. 

This brief introduction has been intended to give the reader an idea of what the electrostatic potential is and how it can be a useful analytical tool for someone interested in molecular interactions. An important point to keep in mind is that the concepts and methodology to be discussed can be applied computationally to predict properties of molecules that have not yet been synthesized. 

The definition of the molecular electrostatic potential follows from basic electrostatics. Any distribution of electrical charge creates an electrical potential V(r) in the surrounding space. Take for example an assembly of point charges Q, located at positions r,. The resulting electrical potential at any point r is simply the sum of Coulombic potentials, as given in equation (2)  

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J. S. Murray, P. Politzer, Electrostatic Potentials Chemical Applications. In Encyc. Comp. Chem. P. von Rague Schleyer, (Ed.), Wiley Chichester, 1998. 

Murray JS, Politzta- P (1998) Electrostatic potentials chemical applications. In Schleyer PvR (ed) Encyclopedia of computational chemistry. Wiley, Chichester, UK... 

AMBER A Program for Simulation of Biological and Organic Molecules Atoms in Molecules Charge Flux Electronic Wavefunctions Analysis Electrostatic Potentials Chemical Applications Free Energy Changes in Solution Natural Bond Orbital Methods Natural Orbitals. 

The electrostatic potential V (r) (see Electrostatic Potentials Chemical Applications) has also been widely used in the interpretation of molecular properties. Although its importance as a tool i or analysis of electronic wavefunctions has... 

Atoms in Molecules Electrostatic Potentials Chemical Applications Localized MO SCF Methods Molecular Magnetic Properties Natural Bond Orbital Methods Natural Orbitals Population Analyses for Semiempirical Methods Shape Analysis. 

One of the simplest examples of electrostatic catalysis is the acceleration of the 1,5-hydride shift in cyclopentadiene by the influence of Li" " cations. The reaction proceeds via an asymmetric transition state that is 34 kJ mol more stable than the symmetric ground state. It could be shown that this extra stabilization (catalytic rate acceleration) is completely due to the effect of the electrostatically bound cation. Difference in cation complexation energies could be adequately illustrated by molecular electrostatic potential (MEP) maps for the ground and transition states (see Electrostatic Potentials Chemical Applications). The maps are symmetric and asymmetric for the ground and transition states, respectively, and indicate larger cation attraction for the latter. 

Catalyst Design Electrostatic Potentials Chemical Applications Transition State Theory Zeolites Applications of Computational Methods. 

Artificial Intelligence in Chemistry Chemical Engineering Expert Systems Chemometrics Multivariate View on Chemical Problems Electrostatic Potentials Chemical Applications Environmental Chemistry QSAR Experimental Data Evaluation and Quality Control Fuzzy Methods in Chemistry Infrared Data Correlations with Chemical Structure Infrared Spectra Interpretation by the Characteristic Frequency Approach Machine Learning Techniques in Chemistry NMR Data Correlation with Chemical Structure Protein Modeling Protein Structure Prediction in ID, 2D, and 3D Quality Control, Data Analysis Quantitative Structure-Activity Relationships in Drug Design Quantitative Structure-Property Relationships (QSPR) Shape Analysis Spectroscopic Databases Structure Determination by Computer-based Spectrum Interpretation. 

Electrostatic Potentials Chemical Applications Parameterization of Semiempirical MO Method. 

Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field Electrostatic Potentials Chemical Applications MNDO PM3 Semiempirical Methods Transition Metals SINDOl Parameterization and Application. 

Peter Politzer University of New Orleans, LA, USA Electrostatic Potentials Chemical Applications 2 912... 

M. P. Allen, D. J. Tildesley, Computer Simulation of Liquids Oxford, Oxford (1987). Chemical Applications of Atomic and Molecular Electrostatic Potentials P. Politzer, D. G. Truhlar, Eds., Plenum, New York (1981). 

Politzer, P. and Murray, J.S. (1990) Chemical applications of molecular electrostatic potentials, Transactions ACA, 26, 23-39. 

Our discussion in this chapter will focus on the use of the electrostatic potential as a means to understanding and predicting chemical interactions. First, we will examine some of its properties and important features. Next, we will discuss methodology. Finally we will review some recent applications of the electrostatic potential in areas such as hydrogen bonding, molecular recognition, and understanding and prediction of a variety of physio-chemical properties related to molecular interactions. Our intent has not been to provide a complete survey of the ways in which the potential has been used, many of which are described elsewhere (Politzer and Daiker 1981 Politzer, Laurence, and Jayasuriya 1985 Politzer and Murray 1990 Politzer and Murray 1991 Politzer and Truhlar 1981 Scrocco and Tomasi 1973), but rather to focus on some diverse examples. 

Politzer, P. 1981. Relationships between Energies of Atoms and Molecules and the Electrostatic Potentials at their Nuclei. In Chemical Applications of Atomic and... 

Politzer, P., and J. S. Murray. 1990. Chemical Applications of Molecular Electrostatic Potentials. Trans. Amer. Cryst. Assoc. 26, 23. 

Pullman, A., and B. Pullman. 1981a. The Electrostatic Molecular Potential of the Nucleic Acids. In Chemical Applications of Atomic and Molecular Electrostatic Potentials. Plenum Press, New York. 

The final part is devoted to a survey of molecular properties of special interest to the medicinal chemist. The Theory of Atoms in Molecules by R. F.W. Bader et al., presented in Chapter 7, enables the quantitative use of chemical concepts, for example those of the functional group in organic chemistry or molecular similarity in medicinal chemistry, for prediction and understanding of chemical processes. This contribution also discusses possible applications of the theory to QSAR. Another important property that can be derived by use of QC calculations is the molecular electrostatic potential. J.S. Murray and P. Politzer describe the use of this property for description of noncovalent interactions between ligand and receptor, and the design of new compounds with specific features (Chapter 8). In Chapter 9, H.D. and M. Holtje describe the use of QC methods to parameterize force-field parameters, and applications to a pharmacophore search of enzyme inhibitors. The authors also show the use of QC methods for investigation of charge-transfer complexes. 

As another example, the functional expression for the energy in terms of p(r) is known only approximately. However exact formulas have been developed that relate the energies of atoms and molecules to the electrostatic potentials at their nuclei [49-52], This has been done as well for the chemical potentials (electronegativities) of atoms [53]. Thus, both the intrinsic significance and the practical applications of the electrostatic potential continue to be active areas of investigation. 

The book covers a gamut of related topics such as methods for determining atoms-in-molecuies, population analysis, electrostatic potential, molecular quantum similarity, aromaticity, and biological activity. It also discusses the role of reactivity concepts in industrial and other practical applications. Whether you are searching for new products or new research projects, this is the ultimate guide for understanding chemical reactivity. 

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