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Pratim Kumar Chattaraj - One of the best experts on this subject based on the ideXlab platform.
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a comparative study to predict regioselectivity Electrophilicity and nucleophilicity with fukui function and hirshfeld charge
Theoretical Chemistry Accounts, 2019Co-Authors: Bin Wang, Pratim Kumar Chattaraj, Chunying Rong, Shubin LiuAbstract:Chemical reactivity properties such as regioselectivity, Electrophilicity and nucleophilicity are important chemical concepts, yet their understanding and quantification are still far from being accomplished. Applying density functional theory (DFT) to appreciate these properties is one route to pursue in the literature. In this work, we present a comparative study to benchmark two approaches in DFT to predict regioselectivity, Electrophilicity and nucleophilicity: one with the Hirshfeld charge and the other with the Fukui function. We also examine the impact of 15 different ways to compute atomic charges on the performance of their predictions about these chemical reactivity properties. Our results show that the Hirshfeld charge is able to reliably determine regioselectivity and simultaneously accurately quantify both Electrophilicity and nucleophilicity. The Fukui function behaves reasonably well for the prediction of Electrophilicity but performs poorly for nucleophilicity. Among all other atomic charges examined in this study, it is only the Voronoi deformation density charge that yields the similar result as the Hirshfeld charge. As the first systematic benchmark study in the literature to compare the two available approaches in DFT about reactivity predictions, this work should fill in the needed knowledge gap and provide an impetus for the future development of chemical reactivity theory using DFT language.
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hydrophobicity versus Electrophilicity a new protocol toward quantitative structure toxicity relationship
Chemical Biology & Drug Design, 2019Co-Authors: Ranita Pal, Pratim Kumar Chattaraj, Gourhari Jana, Shamik SuralAbstract:QSAR/QSPR/QSTR modeling and chemical grouping approach are presented to provide information on the biological properties of various substituted benzene derivatives. A novel descriptor, viz., the square of Electrophilicity index (ω2 ) is proposed to provide a compact correlation between the structure of the compounds and their biological properties which is marginally superior to Electrophilicity index (ω) or ω3 in most of the cases, and more or less similar to that obtained from hydrophobicity (or lipophilicity). Besides the straightforward case study, neural networks (NN) are employed to ascertain the robustness of the QSAR model obtained by implementing multiple linear regression (MLR).
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on the validity of the maximum hardness principle and the minimum Electrophilicity principle during chemical reactions
Journal of Physical Chemistry A, 2013Co-Authors: Sudip Pan, Miquel Sola, Pratim Kumar ChattarajAbstract:Hardness and Electrophilicity values for several molecules involved in different chemical reactions are calculated at various levels of theory and by using different basis sets. Effects of these aspects as well as different approximations to the calculation of those values vis-a-vis the validity of the maximum hardness and minimum Electrophilicity principles are analyzed in the cases of some representative reactions. Among 101 studied exothermic reactions, 61.4% and 69.3% of the reactions are found to obey the maximum hardness and minimum Electrophilicity principles, respectively, when hardness of products and reactants is expressed in terms of their geometric means. However, when we use arithmetic mean, the percentage reduces to some extent. When we express the hardness in terms of scaled hardness, the percentage obeying maximum hardness principle improves. We have observed that maximum hardness principle is more likely to fail in the cases of very hard species like F–, H2, CH4, N2, and OH appearing in t...
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Electrophilicity equalization principle
Journal of Physical Chemistry Letters, 2010Co-Authors: Pratim Kumar Chattaraj, Santanab Giri, Soma DuleyAbstract:A new electronic structure principle, namely, the principle of Electrophilicity equalization, is proposed. A qualitative rationale as well as numerical support for the same is provided. Equalization of electronegativity and hardness implies that of Electrophilicity. Molecular Electrophilicity may be expressed roughly as the geometric mean of the electrophilicities of the isolated atoms.
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electron affinity electronegativity and Electrophilicity of atoms and ions
Journal of Chemical & Engineering Data, 2010Co-Authors: Pratim Kumar Chattaraj, Soma DuleyAbstract:The electron affinity, electronegativity, and Electrophilicity of several neutral atoms and their positive and negative ions are calculated at various levels of theory using different basis sets in the gas phase as well as in the presence of solvent and counterions. The electron affinity and electronegativity of all of the anions and dianions are negative in gas phase, and accordingly the Electrophilicity is unexpectedly large vis-a-vis its quadratic definition. Many of these trends get altered in case the effects of solvent and counterions are taken into account.
Renato Contreras - One of the best experts on this subject based on the ideXlab platform.
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a local extension of the Electrophilicity index concept
Revista de la Sociedad Química de Mexico, 2017Co-Authors: Andres Cedillo, Renato ContrerasAbstract:A local measure of the Electrophilicity has been recently proposed to analyze the chemical reactivity of several kinds of mol- ecules. In this work a theoretical rationalization of the local extension is proposed following the quantitative definition of the molecular electrophilic power and a variational method for the distribution of the transferred charge. A condensation scheme to atoms or fragments follows from its relation to the Fukui function and the local softness. Differences between these quantities are discussed and they are tested in a model system. The analysis shows that the local Electrophilicity is more appropriate to describe differences among a set of substituted molecules.
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invariance of Electrophilicity of independent fragments application to intramolecular diels alder reactions
Chemical Physics Letters, 2010Co-Authors: Jorge Sotodelgado, Luis R Domingo, Arie Aizman, Renato ContrerasAbstract:Abstract We herein demonstrate that the global Electrophilicity may be distributed into fragments within a single molecule by using an empirical partitioning scheme of the electronic chemical potential framed on the chemical potential inequality principle. Group Electrophilicity for several fragments may thereby be defined. Their values show a remarkable stability, independent of the chemical environment they are attached to. The model is applied to asses the chemical reactivity of a series of fragments involved in intramolecular Diels–Alder reactions.
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quantitative characterization of group Electrophilicity and nucleophilicity for intramolecular diels alder reactions
Organic and Biomolecular Chemistry, 2010Co-Authors: Jorge Sotodelgado, Luis R Domingo, Renato ContrerasAbstract:In a previous work (L. R. Domingo, M. J. Aurell, P. Perez and R. Contreras, Tetrahedron 2002, 58, 4417) we proposed that the difference in global Electrophilicity index be taken as a measure of the polarity at the transition state in intermolecular Diels–Alder reactions. We herein extend this model to deal with intramolecular Diels–Alder (IMDA) processes. The transferability of the empirical reactivity rules established for the intermolecular DA reactions to the IMDA reactions is discussed. The analysis based on group Electrophilicity and nucleophilicity in general fails because having two different reactivity patterns within the same molecule hampers a clean classification of Electrophilicity and nucleophilicity of the interacting fragments. We introduce dual philicity indexes E1 and E2 that solve this problem by separating a series of 30 IMDA reactions into two families, namely the diene to dienophile electron flow (DDpF) and the dienophile to diene electron flow (DpDF) processes. The new indexes correctly describe the charge transfer at the transition state and the reaction mechanism expected for the title reactions.
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Electrophilicity of quinones and its relationship with hydride affinity
Chemical Physics Letters, 2009Co-Authors: Paola R Campodonico, Arie Aizman, Renato ContrerasAbstract:In this Letter we show that the Electrophilicity index assesses well the hydride affinity (HA) order of quinones established for a limited number of cases experimentally observed. Further comparisons with predicted HA values for a larger data base suggest that both the Electrophilicity index and HA are tightly related quantities. Furthermore, electrophilic activation/deactivation patterns induced by electron-withdrawing and electron-donating groups may be consistently accounted for by the model. These results open the possibility of predicting HA for quinones not evaluated experimentally up to date.
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chapter 9 the Electrophilicity index in organic chemistry
Theoretical and Computational Chemistry, 2007Co-Authors: Patricia Perez, Luis R Domingo, Arie Aizman, Renato ContrerasAbstract:Abstract We review in this chapter the applications of theoretical scales of global and local Electrophilicity to rationalize the reactivity and selectivity for a significant number of reactions in organic chemistry. The model is based on the global Electrophilicity index, formerly introduced by Maynard et al. and further formalized by Parr et al. The global Electrophilicity index categorizes, within a unique absolute scale, the propensity of electron acceptors to acquire additional electronic charge from the environment. The local extension of this index provides useful information about the active sites of electrophiles, thereby allowing the characterization of the intramolecular selectivity in these systems. These concepts will be illustrated for a series of chemical reactions in organic chemistry, including polar cycloadditions and electrophilic addition reactions, substrate selectivity in electrophilic aromatic substitution (Friedel-Crafts) reactions, hydrolysis of carbonyl compounds, the reactivity of carbenes and carbenium ions and the superElectrophilicity of dicarbenium, oxonium and dicarboxylic acids.
Patricia Perez - One of the best experts on this subject based on the ideXlab platform.
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intrinsic relative scales of Electrophilicity and nucleophilicity
Journal of Physical Chemistry A, 2013Co-Authors: Eduardo Chamorro, Mario Duquenorena, Rafael Notario, Patricia PerezAbstract:The formulation of the second-order perturbation approach to the stabilization energy of the A–B interacting species due to charge transfer is revisited. Intrinsic (i.e., electronic) theoretical indices for both relative Electrophilicity and nucleophilicity are proposed for any electrophile (A)–nucleophile (B) pairs of combining species. By using the new descriptors, an electronic analogue to the Mayr–Patz linear free relationship has been successfully tested in the context of available experimental evidence reported for reactions of primary and secondary amines with benzhydrylium ions.
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an analysis of the regioselectivity of 1 3 dipolar cycloaddition reactions of benzonitrile n oxides based on global and local Electrophilicity and nucleophilicity indices
European Journal of Organic Chemistry, 2009Co-Authors: Luis R Domingo, Eduardo Chamorro, Patricia PerezAbstract:The regioselectivity of the 1,3-dipolar cycloaddition (13DC) reactions of benzonitrile N-oxides (BNOs) with electrophilic and nucleophilic alkenes has been analyzed by using global and local nucleophilicity and Electrophilicity reactivity indices defined within the conceptual DFT. The BNOs react with electron-deficient and electron-rich ethylenes, but the regioselectivities of these polar reactions are different. Whereas the reactions with electron-rich ethylenes are completely regioselective, yielding 5-isoxazolines, a change in the regioselectivity is observed in the reactions with electron-deficient ethylenes, which yield a mixture of 4- and 5-isoxazolines. Analysis of the energies, geometries, and electronic structures of the transition-state structures involved in the 13DC reactions between the BNOs and two electronically activated ethylenes are in complete agreement with the analysis of the global and local Electrophilicity and nucleophilicity reactivity indices.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
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a comparison between theoretical and experimental models of Electrophilicity and nucleophilicity
Journal of Molecular Structure-theochem, 2009Co-Authors: Eduardo Chamorro, Mario Duquenorena, Patricia PerezAbstract:Abstract Four different theoretical models of Electrophilicity and nucleophilicity has been discussed in the light of experimental available evidence for a series of 20 benzhydrylium ions taken as reference electrophilic systems and 16 primary and secondary amines as nucleophilic systems. It is shown that the theoretical scales are linearly related to the well-known experimental ones based on the Electrophilicity (E) and nucleophilicity (N and s ) parameters derived by Mayr from the rate constants k20 °C associated to general electrophile–nucleophile combinations, log k20 °C = s(N + E).
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a comparative analysis of the Electrophilicity of organic molecules between the computed ips and eas and the homo and lumo energies
Chemical Physics Letters, 2007Co-Authors: Luis R Domingo, Jose Antonio Lopez Saez, Patricia PerezAbstract:Abstract The Electrophilicity index, ω , of a series of substituted ethylenes used in some relevant organic reactions has been evaluated from the ionization potential (IP) and the electron affinity (EA) computed by vertical ionization at the B3LYP/aug-cc-PVTZ level. The corresponding Electrophilicity values are well correlated with those obtained from the HOMO and LUMO energies of the neutral molecules. The good linear correlation found between ω (I,A) and ω (H,L) LBS , and between ω (H,L) LBS and ω (H,L) SBS allows to confirm the use of the easily available B3LYP/6-31G ∗ HOMO and LUMO energies to obtain reasonable values of the global Electrophilicity index of organic molecules.
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chapter 9 the Electrophilicity index in organic chemistry
Theoretical and Computational Chemistry, 2007Co-Authors: Patricia Perez, Luis R Domingo, Arie Aizman, Renato ContrerasAbstract:Abstract We review in this chapter the applications of theoretical scales of global and local Electrophilicity to rationalize the reactivity and selectivity for a significant number of reactions in organic chemistry. The model is based on the global Electrophilicity index, formerly introduced by Maynard et al. and further formalized by Parr et al. The global Electrophilicity index categorizes, within a unique absolute scale, the propensity of electron acceptors to acquire additional electronic charge from the environment. The local extension of this index provides useful information about the active sites of electrophiles, thereby allowing the characterization of the intramolecular selectivity in these systems. These concepts will be illustrated for a series of chemical reactions in organic chemistry, including polar cycloadditions and electrophilic addition reactions, substrate selectivity in electrophilic aromatic substitution (Friedel-Crafts) reactions, hydrolysis of carbonyl compounds, the reactivity of carbenes and carbenium ions and the superElectrophilicity of dicarbenium, oxonium and dicarboxylic acids.
R Parthasarathi - One of the best experts on this subject based on the ideXlab platform.
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Electrophilicity based charge transfer descriptor
Journal of Physical Chemistry A, 2007Co-Authors: J Padmanabhan, R Parthasarathi, Venkatesan Subramanian, Pratim Kumar ChattarajAbstract:In line with the charge transfer (ΔNmax = −μ/η) proposed by Parr et al. (Parr, R. G.; Szentpaly, L. V.; Liu, S. J. Am. Chem. Soc. 1999, 121, 1922), we propose an Electrophilicity-based charge transfer (ECT) descriptor in this paper and validate it through the interaction between a series of chlorophenols and DNA bases. Application of ECT can be extended to the interaction of any toxin with the biosystem.
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analyzing toxicity through Electrophilicity
Molecular Diversity, 2006Co-Authors: D R Roy, R Parthasarathi, V Subramanian, Pratim Kumar Chattaraj, Utpal Sarkar, Analava Mitra, J Padmanabhan, S Van Damme, Patrick BultinckAbstract:The toxicological structure-activity relationships are investigated using conceptual DFT based descriptors like global and local electrophilicities. In the present work the usefulness of Electrophilicity in predicting toxicity of several polyaromatic hydrocarbons (PAH) is assessed. The toxicity is expressed through biological activity data (pIC50) defined as molar concentration of those chemicals necessary to displace 50% of radiolabeled tetrachlorodibenzo-p-dioxin (TCDD) from the arylhydrocarbon (Ah) receptor. The experimental toxicity values (pIC50) for the electron acceptor toxin like polychlorinated dibenzofurans (PCDF) are taken as dependent variables and the DFT based global descriptor Electrophilicity index (omega) is taken as independent variable in the training set. The same model is then tested on a test set of polychlorinated biphenyls (PCB). A good correlation is obtained which vindicates the importance of these descriptors in the QSAR studies on toxins. These toxins act as electron acceptors in the presence of biomolecules whereas aliphatic amines behave as electron donors some of which are also taken into account for the present work. The toxicity values of the aliphatic amines in terms of the 50% inhibitory growth concentration (IGC50) towards ciliate fresh-water protozoa Tetrahymena pyriformis are considered. Since there is no global nucleophilicity we apply local nucleophilicity (omegamax+) as the descriptor in this case of training set. The same regression model is then applied to a test set of amino alcohols. Although the correlation is very good the statistical analysis reflects some cross validation problem. As a further check the amines and amino alcohols are used together to form both the training and the test sets to provide good correlation. It is demonstrated that the toxicity of several toxins (both electron donors and acceptors) in the gas and solution phases can be adequately explained in terms of global and local electrophilicities. Amount of charge transfer between the toxin and the biosystem, simulated as nucleic acid bases and DNA base pairs, indicates the importance of charge transfer in the observed toxicity. The major strength of the present analysis vis-a-vis the existing ones rests on the fact that it requires only one descriptor having a direct relationship with toxicity to provide a better correlation. Importance of using the information from both the toxin and the biosystem is also analyzed.
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an Electrophilicity based analysis of toxicity of aromatic compounds towards tetrahymena pyriformis
Qsar & Combinatorial Science, 2006Co-Authors: Debesh R Roy, R Parthasarathi, V Subramanian, Pratim K ChattarajAbstract: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 (R), variance adjusted to degrees of freedom (R 2 adj ) and variance of leave-one-out cross-validation (R 2 CV ) 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.
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Electrophilicity as a possible descriptor for toxicity prediction
Bioorganic & Medicinal Chemistry, 2005Co-Authors: D R Roy, R Parthasarathi, Venkatesan Subramanian, B Maiti, Pratim Kumar ChattarajAbstract:Electrophilicity is one of the cardinal chemical reactivity descriptors successfully employed in various molecular reactivity studies within a structure-activity relationship parlance. The applications of this quantity in the modeling of toxicological properties have inspired us to perform a more exhaustive study in order to test and/or to validate the application of Electrophilicity in assessing its chemical and toxicological potential. For this reason the toxicity of a large data set of molecules comprising 252 aliphatic compounds on the Tetrahymena pyriformis is studied. A quantitative structure-activity relationship analysis enabled us to model toxicity in terms of global and local electrophilicities, which provide a reasonably good prediction of aliphatic toxicity. It is heartening to note that the global and local Electrophilicity values together can explain the toxicity of a large variety of aliphatic compounds nicely without resorting to any other descriptor or other microscopic/macroscopic physicochemical properties as is the situation in all other QSAR studies.
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variation of Electrophilicity during molecular vibrations and internal rotations
Theoretical Chemistry Accounts, 2005Co-Authors: R Parthasarathi, Venkatesan Subramanian, M Elango, Pratim Kumar ChattarajAbstract:The interrelationships between global reactivity descriptors such as chemical hardness, chemical potential, polarizability and Electrophilicity and associated electronic structure principles were investigated in detail by considering distortion along the normal coordinates from the equilibrium structure and internal rotation. The necessary conditions on the extremum of Electrophilicity were probed along with other electronic structure principles associated with the global reactivity descriptors. It was observed that an extremum in Electrophilicity is obtained where both chemical potential and chemical hardness attain their respective exiremal values in course of the molecular vibrations as well as internal rotations.
Herbert Mayr - One of the best experts on this subject based on the ideXlab platform.
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Quantification of the Electrophilicity of Benzyne and Related Intermediates
Journal of the American Chemical Society, 2016Co-Authors: Noah F. Fine Nathel, Herbert Mayr, Lucas A. Morrill, Neil K. GargAbstract:The determination of reactivity parameters for short-lived intermediates provides an indispensable tool for synthetic design. Despite that Electrophilicity parameters have now been established for more than 250 reactive species, the corresponding parameters for benzyne and related intermediates have not been uncovered. We report a study that has allowed for the quantification of benzyne’s Electrophilicity parameter. Our approach relies on the strategic use of the diffusion-clock method and also provides Electrophilicity parameters E for other substituted arynes.
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electrophilicities of benzaldehyde derived iminium ions quantification of the electrophilic activation of aldehydes by iminium formation
Journal of the American Chemical Society, 2013Co-Authors: Roland Appel, Saloua Chelli, Takahiro Tokuyasu, Konstantin Troshin, Herbert MayrAbstract:Rate constants for the reactions of benzaldehyde-derived iminium ions with C-nucleophiles (enamines, silylated ketene acetals, and enol ethers) have been determined photometrically in CH3CN solution and used to determine the Electrophilicity parameters E of the cations defined by the correlation log k20°C = sN(E + N) (Mayr, H.; et al. J. Am. Chem. Soc.2001, 123, 9500–9512). With Electrophilicity parameters from E = −10.69 (Ar = p-MeOC6H4) to E = −8.34 (Ar = p-CF3), the iminium ions Ar–CH═NMe2+ have almost the same reactivities as analogously substituted arylidenemalononitriles Ar–CH═C(CN)2 and are 10 orders of magnitude more reactive than the corresponding aldehydes. The rate constants for the reactions of iminium ions with amines and water in acetonitrile are 103–105 times faster than predicted by the quoted correlation, which is explained by the transition states which already experience the anomeric stabilization of the resulting N,N- and O,N-acetals.
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Electrophilicity parameters of 5 benzylidene 2 2 dimethyl 1 3 dioxane 4 6 diones benzylidene meldrum s acids
Journal of Organic Chemistry, 2008Co-Authors: Oliver Kaumanns, Herbert MayrAbstract:Kinetics of the reactions of four benzylidene Meldrum's acids 1 with acceptor-substituted carbanions 2 were studied photometrically in DMSO at 20 degrees C. The reactions follow second-order kinetics, and the second-order rate constants were found to follow the correlation log k2 (20 degrees C) = s(N + E) (eq 1), which was used to calculate the Electrophilicity parameters E for compounds 1. Hammett correlations are given, which allow one to assign Electrophilicity parameters for various beta,beta-acceptor substituted styrenes and thus to predict a large number of absolute rate constants for a manifold of Michael additions. The reactions of primary and secondary amines are approximately 2 orders of magnitude faster than predicted by the correlation (1), supporting transition states which are stabilized by hydrogen bridges from NH to the carbonyl groups of the benzylidene Meldrum's acids.
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Electrophilicity parameters for 2 benzylidene indan 1 3 diones a systematic extension of the benzhydrylium based Electrophilicity scale
Organic and Biomolecular Chemistry, 2007Co-Authors: Stefan T. A. Berger, Florian Seeliger, Florian R. Hofbauer, Herbert MayrAbstract:Kinetics of the reactions of four 2-benzylidene-indan-1,3-diones (1a–d) with carbanions (2a–l) have been studied photometrically in dimethyl sulfoxide solution at 20 °C, and the Electrophilicity parameters E were determined by the linear free energy relationship log k2(20 °C) = s(N + E) (eqn (1)). The rate-determining step of these reactions is the nucleophilic attack of the carbon nucleophile at the double bond of the Michael acceptor. Comparisons with literature data show that the linear free energy relationship (eqn (1)) allows the semiquantitative prediction of the reactivities of 2-benzylidene-indan-1,3-diones towards various nucleophiles.
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Electrophilicity of 5-benzylidene-1,3-dimethylbarbituric and -thiobarbituric acids.
The Journal of Organic Chemistry, 2007Co-Authors: Florian Seeliger, Grigoriy Ya Remennikov, Stefan T. A. Berger, Kurt Polborn, Herbert MayrAbstract:The kinetics of reactions of acceptor-stabilized carbanions 2a−m with benzylidenebarbituric and -thiobarbituric acids 1a−e has been determined in a dimethyl sulfoxide solution at 20 °C. Second-order rate constants were employed to determine the Electrophilicity parameters E of the benzylidenebarbituric and -thiobarbituric acids 1a−e according to the correlation equation log k(20 °C) = s(N + E). With E parameters in the range of −10.4 to −13.9, the electrophilicities of 1a−e are comparable to those of analogously substituted benzylidenemalononitriles.