Oxidation-reduction characteristics of octahydrochalcogenoxanthenes and octahydroxanthylium cations

Берберова, Н. Т.; Blinokhvatov, A. F.; Archegova, A. S.; Klimov, E. S.; Shpakov, A. E.; Okhlobystin, O. Yu.

doi:10.1007/bf00633213

Cited by 4 publications

(2 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Table 2 gives the calculated values of the hydride ion, hydrogen atom, and proton affinities and also the ionization potentials of the named molecular systems. The results of the calculations show that the experimental "hydride" mobility series S > O ≈ Se [47][48][49] does not contradict the ionization potentials (IP) of molecules 1-6 or the hydrogen atom affinity (HAA) of the radicals formed by removal of the hydrogen atom at position 4 of the heterocycle from the initial systems 1-6.…”

Section: Subjects Of Investigationmentioning

confidence: 94%

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

Pankratov

Drevko

2005

Chem Heterocycl Compd

View full text Add to dashboard Cite

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.

show abstract

Section: Subjects Of Investigationmentioning

confidence: 94%

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

Pankratov

Drevko

2005

Chem Heterocycl Compd

View full text Add to dashboard Cite

show abstract

“…As a result of studies 44,45 concerned with the equilibrium of heteroaromatic cation -chalcogenopyran, and the determination 46 of a comparative reactivity series, it was established that thiopyrans are more capable or removing a "hydride ion" than the oxygen and selenium analogs.…”

Section: Mechanismmentioning

confidence: 99%

An approach to quantum chemical consideration of "hydride" transfer reaction

Pankratov

Drevko

2004

JSCS

View full text Add to dashboard Cite

An approach to the quantum chemical study of "hydride ion" transfer has been proposed, according to which the sequences of changes in ionization potentials, enthalpies and free energies of the affinities to the hydride ion, to the hydrogen atom and to the proton of substrates molecules and their derivatives (cations, radicals, anions), are compared with the experimentally substantiated series of "hydride" mobility. It has been established that the experimental series of "hydride" mobility for six chalcogenopyrans based on "semicyclic" 1,5-diketones is in conformity with the computed ionization potentials of themolecules, and with the affinity of the corresponding radicals to the hydrogen atom involved in the transfer. The direct splitting-out of the hydride ion and the primary deprotonation of the substrates followed by the withdrawal of two electrons was elucidated to be unlikely. Feasible are the mechanisms of "hydride" mobility, the first step of which consists of electron or hydrogen atom transfer from the chalcogenopyrans molecules.

show abstract

5.11 References for 5

Neugebauer¹

Landolt-Börnstein - Group II Molecules and Radicals

View full text Add to dashboard Cite

Oxidation-reduction characteristics of octahydrochalcogenoxanthenes and octahydroxanthylium cations

Cited by 4 publications

References 1 publication

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

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

An approach to quantum chemical consideration of "hydride" transfer reaction

5.11 References for 5

Contact Info

Product

Resources

About