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Pankratov, A. N.; Shchavlev, Andrew E.

doi:10.1023/a:1009438517429

Cited by 20 publications

(13 citation statements)

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“…We found that the MNDO, AM1, and PM3 methods correctly reproduce the most important thermodynamic and molecular characteristics [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47], electronegativities, and inductive and mesomeric parameters of groups of atoms [48,49] is series of compounds. Among these methods, only PM3 yields reasonable results for the heats of formation of nitroso compounds [24,30] and dimethyl sulfone [32].…”

Section: Resultsmentioning

confidence: 99%

Quantitative structure-property relationships in the series of diazonium cations, intermediate products in the synthesis of analytical forms and dyes

et al. 2005

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The azocoupling reaction of aromatic amines and phenols with aryldiazonium cations is of great importance for the production of dyes [1][2][3] and in analytical chemistry [4].Diazonium cations can be reduced either chemically or electrochemically [5][6][7][8][9][10][11][12]. For many compounds, the abilities to be subjected to electrophilic (nucleophilic) attack and to undergo oxidation (reduction) vary in parallel [13][14][15][16]. The susceptibility of diazo cations to reduction can serve as a measure of their electrophilic activity. Therefore, the a priori prediction of the reduction potentials and electron affinities of diazonium cations of the given structure and their subsequent directed synthesis is reasonable for the selection of the optimum reaction rates of the formation of azo dyes and analytical forms.Diazonium cations decompose to release molecular nitrogen [2,10,12,17]. To provide high yields of azo compounds and satisfactory accuracy, precision, and other performance characteristics of analytical procedures, it is desirable to avoid this competing reaction and to estimate quantitatively the degree of decomposition of newly synthesized diazonium salts.Among others, the stretching frequencies of the C -N + ≡ N group are a measure of the stability of diazonium cations (and simultaneously an indication of their activity as electrophilic agents) [17][18][19][20][21][22].As will be demonstrated below, vibrational frequencies and electron affinity correlate with the mesomeric dipole moments of substituents in aryldiazonium cations.The aim of this work was to find (based on quantumchemical calculations) quantitative structure-property relationships for the prediction of reduction potentials and some related quantities, electron affinities, stretching frequencies of the C -N + ≡ N group of aryldiazonium cations, and mesomeric dipole moments of groups of atoms.The correlations that are discussed in this work were presented in [23]. EXPERIMENTALCalculations were performed by the PM3 method [24] using the MOPAC program [25,26] with full geometry optimization (Broyden-Fletcher-GoldfarbShanno procedure [27]) using the Thiel algorithm for rapid minimization [28]. Preliminary optimization was performed by the molecular mechanics method (MMX procedure) [29] using the PCMODEL program [29]. In quantum-chemical calculations, we set the condition that the norm of the gradient was no higher than 0.084 kJ mol -1 Å -1 . In some cases, a sufficient decrease in the norm of the gradient was attained by the reject of Thiel rapid minimization (using the option NOTHIEL in the MOPAC program), by the optimization using the Davidon-Fletcher-Powell method (option DFP) [27], and by the combination of the approaches provided by the options NOTHIEL and DFP.For molecules with closed electronic shells, we used the restricted Hartree-Fock (RHF) method [26]. Radicals formed on the reduction of aryldiazonium salts were calculated by the unrestricted Hartree-Fock (UHF) method [26].Abstract -It was demonstrated that the reduction potentials,...

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Section: Resultsmentioning

confidence: 99%

Quantitative structure-property relationships in the series of diazonium cations, intermediate products in the synthesis of analytical forms and dyes

et al. 2005

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“…[29] In the case of the N-substituted diphenylamine 16, the pK a obtained is negative in agreement with the low experimental values reported for diphenylamine itself (0.78), N-methyldiphenylamine (1.71), 4-carboxydiphenylamine (À1.24) or 4-nitrodiphenylamine (À2.78). [42] The pK a obtained for compounds in Group 5, can be discussed in three sets even though they all contain an aliphatic amine (secondary or tertiary). Derivatives 19 and 21 both have two OCH 3 groups attached to the phenyl ring at the ortho positions of the O-alkyl chain containing the amine to be protonated (see Fig.…”

Section: Experimental Pk Amentioning

confidence: 99%

Computational study of the proton affinity and basicity of structurally diverse α₁‐adrenoceptor ligands

Matijssen

Kinsella

Watson

et al. 2011

J of Physical Organic Chem

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The a 1 -adrenoceptor is a target for the treatment of several conditions from hypertension to benign prostatic hyperplasia. In this paper, we describe a new analysis approach to explore the conformational space of several ligands of the a 1 -adrenoceptor and we also present the calculation of their proton affinity and basicity. For each compound a conformational search followed by a semi-empirical optimisation was performed and a selection of conformations for each ligand was subjected to further optimisation using density functional theory methods. Different positions were explored to determine the favoured site of protonation, and then, the proton affinity (in the gas phase) and basicity (using the polarisable continuum model for the aqueous solution) were calculated for each of them. In addition, an alternative method using one explicit water molecule in combination with the polarisable continuum model for aqueous solvent was explored. Moreover, the acid dissociation constant (pK a ) in water of these 26 compounds was calculated because this is an important parameter for a ligand when binding to its receptor. The experimental pK a values of six of these ligands and those of two compounds with a very low and a very large pK a were used to validate the theoretical methodology.

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“…We established the accuracy of reproduction of the most important thermodynamic and molecular characteristics [14-38] and the electronegativity, inductive, and mesomeric parameters of the atomic groups [35,39,40] in series of compounds of various classes with various functional groups by the MNDO, AM1, and PM3 methods. In addition the relativization principle operates [41]; it is quite correct to compare the values of the quantumchemical indices in a series of compounds of similar structure.…”

Section: Subjects Of Investigationmentioning

confidence: 99%

Quantum-Chemical Study of “Hydride” Mobility in the Molecules of Chalcogenopyrans

Pankratov

Drevko

2005

Chem Heterocycl Compd

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An approach is proposed for the quantum-chemical investigation of "hydride ion" transfer based on analysis of the similarity of the order of variation in the ionization potentials, enthalpies, and free energies of affinity to the hydride ion, the hydrogen atom, and the proton in the substrate molecules and also the derivatives of their cations, radicals, and ions to the experimentally established "hydride" series. It was established that the experimental "hydride" mobility series of six chalcogenopyrans based on "semicyclic" 1,5-diketones agrees with the quantum-chemically calculated ionization potentials of the molecules and with the affinity of the respective radicals to the hydrogen atom participating in the transfer. It was found that direct removal of a hydride ion and initial deprotonation of the substrates followed by the removal of two electrons are unlikely. "Hydride" shift mechanisms, in which the first stage is transfer of an electron or hydrogen atom from the chalcogenopyran molecules, are feasible.Reactions including stages that can formally be represented as hydride-ion transfer are of great significance in chemistry [1]. Examples include the transformations of 1,5-dicarbonyl compounds and chalcogenopyrans in a mixture of chalcogenopyrylium salts and chalcogenocyclohexanes or chalcogenopyrylium salts and other reduced products [2]. The following mechanisms of "hydride" transfer have been discussed for a wide range of chemical compounds [1]:1. Direct abstraction of a hydride ion (-H -). 2. Successive ejection of an electron, a proton, and another electron (-e -, -H + , -e -). 3. Removal of an electron and a hydrogen atom (-e -, -H · ). 4. Transfer of a hydrogen atom and an electron (-H · , -e -). 5. Deprotonation followed by the transfer of two electrons (-H + , -e -, -e -). The mechanism of the "minus electron, minus electron, minus proton" type (-e -, -e -, -H + ) should not be realized since the formation of the dication-radical is unlikely.However, in our opinion, there also exists a mechanism not examined in the present paper, involving initial protonation of the heterocycle and a final stage with release of H 2 [3] or another electrically neutral molecule [4]. The possible protonation of a heterocycle at a chalcogen atom was demonstrated conclusively in the papers of Lambert and others [5]. __________________________________________________________________________________________ 1 N.

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Cited by 20 publications

References 13 publications

Quantitative structure-property relationships in the series of diazonium cations, intermediate products in the synthesis of analytical forms and dyes

Quantitative structure-property relationships in the series of diazonium cations, intermediate products in the synthesis of analytical forms and dyes

Computational study of the proton affinity and basicity of structurally diverse α₁‐adrenoceptor ligands

Quantum-Chemical Study of “Hydride” Mobility in the Molecules of Chalcogenopyrans

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Untitled

Cited by 20 publications

References 13 publications

Quantitative structure-property relationships in the series of diazonium cations, intermediate products in the synthesis of analytical forms and dyes

Quantitative structure-property relationships in the series of diazonium cations, intermediate products in the synthesis of analytical forms and dyes

Computational study of the proton affinity and basicity of structurally diverse α1‐adrenoceptor ligands

Quantum-Chemical Study of “Hydride” Mobility in the Molecules of Chalcogenopyrans

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Computational study of the proton affinity and basicity of structurally diverse α₁‐adrenoceptor ligands