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Electrophilicity Index (electrophilicity + index)

Distribution by Scientific Domains

Chemistry	100%

Selected Abstracts

An Electrophilicity Based Analysis of Toxicity of Aromatic Compounds Towards Tetrahymena Pyriformis

MOLECULAR INFORMATICS, Issue 2 2006
R. Roy
Abstract Electrophilicity index is one of the important quantum chemical descriptors in describing toxicity or biological activities of the diverse classes of chemicals to bio-systems in the context of development of Quantitative Structure Activity Relationship (QSAR). In this study a large number of selected 174 aromatic compounds containing phenols, nitrobenzenes and benzonitriles are chosen as the training set to verify their toxic potency to Tetrahymena pyriformis in the light of electrophilicity. A systematic analysis has been made to find out the electron donation/acceptance nature of these model compounds by comparing their electronegativity values with those of the NA bases/DNA base pairs. The training sets are classified into two groups, viz., the electron donor group comprising 97 phenol derivatives and the electron acceptor group consisting of 77 nitrobenzenes and benzonitriles grouped together. Regression analysis in terms of correlation coefficient (), variance adjusted to degrees of freedom () and variance of leave-one-out cross-validation () has been made for both the electron donor and acceptor aromatic groups to predict the toxicity values of these model compounds to Tetrahymena pyriformis. It is heartening to note that the global and local electrophilicity indices along with the total Hartree-Fock energy can explain more than 80% of cross-validation variance of data of those aromatic molecules. [source]

Solvent effect on the reactivity of CIS -platinum (II) complexes: A density functional approach

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 8 2008
Pubalee Sarmah
Abstract The structure and chemical reactivity of some selected cis -platinum(II) complexes, including clinically used drug molecules, cisplatin, carboplatin, and oxaliplatin are investigated using density functional theory (DFT) calculations. Calculated geometries of the complexes are in agreement with their available X-ray data. The global and local reactivity descriptors, such as hardness, chemical potential, electrophilicity index, Fukui function, and local philicity are calculated to investigate the usefulness of these descriptors for understanding the reactive nature and reactive sites of the complexes. Inclusion of solvent effect shows that both global and local descriptors change the trend of reactivity with respect to their trend in the gas phase. The stability of the complexes increases with the inclusion of water molecules. Simple regression analysis is applied to build up a quantitative structure-activity relationship (QSAR) model based on DFT derived electrophilicity index for the Pt(II) complexes against A2780 human ovarian adenocarcinoma cell line to establish the importance of the descriptor in predicting cytotoxicity. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source]

Electronic structure and physicochemical properties of selected penicillins

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2007
Catalina Soriano-Correa
Abstract Traditionally, penicillins have been used as antibacterial agents due to their characteristics and widespread applications with few collateral effects, which have motivated several theoretical and experimental studies. Despite the latter, their mechanism of biological action has not been completely elucidated. We present a theoretical study at the Hartree,Fock and density functional theory (DFT) levels of theory of a selected group of penicillins such as the penicillin-G, amoxicillin, ampicillin, dicloxacillin, and carbenicillin molecules, to systematically determine the electron structure of full ,-lactam antibiotics. Our results allow us to analyze the electronic properties of the pharmacophore group, the aminoacyl side-chain, and the influence of the substituents (R and X) attached to the aminoacyl side-chain at 6, (in contrast with previous studies focused at the 3, substituents), and to corroborate the results of previous studies performed at the semiempirical level, solely on the ,-lactam ring of penicillins. Besides, several density descriptors are determined with the purpose of analyzing their link to the antibacterial activity of these penicillin compounds. Our results for the atomic charges (fitted to the electrostatic potential), the bond orders, and several global reactivity descriptors, such as the dipole moments, ionization potential, hardness, and the electrophilicity index, led us to characterize: the active sites, the effect of the electron-attracting substituent properties and their physicochemical features, which altogether, might be important to understand the biological activity of these type of molecules. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source]

Why do Electron-Deficient Dienes React Rapidly in Diels,Alder Reactions with Electron-Deficient Ethylenes?

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 23 2004
A Density Functional Theory Analysis
Abstract The Diels,Alder reaction of the electron-deficient (ED) dimethyl 2,3-dimethylenesuccinate with two electron-rich (ER) and two ED ethylenes has been studied at the B3LYP/6-31G* level of theory. The analysis of the geometry and electronic structure of the transition state of the reaction with the ED dimethyl 2-methylenemalonate along with the analysis of the global and local electrophilicity indices of the reagents provide an explanation of the participation of this ED diene as nucleophile against powerful electrophiles in polar Diels,Alder reactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]