N. D. Chuvylkin

Bio: N. D. Chuvylkin is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Chemical shift & Radical. The author has an hindex of 3, co-authored 14 publications receiving 38 citations.

Acyclic and cyclic forms of the radicals HO4⋅ CH3O4⋅ and C2H5O4·: ab initio quantum chemical calculations

Abstract: Acyclic and cyclic structures and total energies of radicals HO4⋅ CH3O4⋅ and C2H5O4· were calculated by ab initio quantum chemical methods. Depending on the computational method and basis sets used, the cyclic conformer of the HO4· radical is 4.8 to 7.3 kJ mol-1 more stable than the acyclic one. For the first two representatives of the homologous series of alkyl tetraoxyl radicals, CH3O4· and C2H5O4, MP2/6-311++G** calculations predict insignificant energy differences (1.2 kJ mol-1) between six-membered cyclic and acyclic conformers. Apparently, these radicals can exist in both forms.

ESR and quantum chemical studies of the structures and thermal transformations of the radical cations of vinylcyclopropane in irradiated frozen Freon matrices. Simulation of radical processes in solids

Abstract: Thermal transformations of vinylcyclopropane radical cations (VCP+) in X-ray-irradiated frozen Freon matrices (CFCl2CF2Cl and CFCl3) were studied by ESR; radical processes involving VCP+ in solid VCP were simulatedGauche- andanti-VCP + were found to be the primary radical cations, however, the former, unlike the latter, is stable only under “gas-phase” conditions The thermodynamic equilibrium betweenanti-VCP+ and its less stable distonic form,dist(90,0)-C 5H8 +, is established in frozen Freon matrices and the VCP host matrix; the structure of dist(90,0)****-C 5H8 + is stabilized by a molecule ofanti-VCP In CFC3, along with dist(90,0)-C5H8 +,π-dimeric resonance [anti-VCP]2 + complex was detected A general scheme of the transformations of VCP+ in the solid phase has been proposed

Esr and quantum-chemical studies of the structure and thermal transformations of vinylcyclopropane radical cations in irradiated frozen freon matrices - simulation of radical processes in the gas-phase

Abstract: Thermal trasfomations of vinylcyclopropane (VCP) radical cations (RC) in X-ray irradiated frozen Freon matrices, CFCl2CF2Cl and CFCl3, were studed by ESR. Radical processes involving VCP.+ in very rarefied and moderately thickened gaseous VCP were simulated. Monomolecular cleavage of the cyclopropane ring ofgauche-VCP.+ (1) occurs to give the more thermally stable distonic radical cationdist(0.90)-C5H8.+ (3). As the density of VCP increases RC3 adds at the double bond ofanti-VCP to give the distonic RC,.CH2CH2CHCH(CH2)3CHCHCH2+ (5). Under the same conditions, the less thermally stableanti-VCP.+(2) undergoes monomolecular isomerization into RC1 or reacts withanti-VCP with the rearrangement (as in the condensed phase) to give its distonic form,dist(90.0)-C5H8.+ (4). The MNDO-UHF method was adapted for quantum-chemical analysis of the constants of isotropic hyperfine coupling with1H and13C nuclei in neutral and charged hydrocabon radicals, since the standard version of this method inadequately reproduces the structural parameters of low-symmetry (C1,Cs) paramagnetic species. A quantum-chemical analysis of the radiospectroscopic information and of the stereoelectronic control of thermal transformations of conformers of RC1 and2 into their structurally nonequivalent distonic forms3 and4, respectively, was carried out.

Quantum-chemical and spectroscopic studies of structures of 1 : 2 complexes of carbonyl compounds with aluminum halides

Abstract: Quantum-chemical calculations of model systems, namely, benzaldehyde and its 1 : 1 and 1 : 2 complexes with AlCl3, were carried out by the MNDO method. In the 1 : 2 complex, a bridging Al-Cl-Al bond occurs. Apparently, this complex is stabilized through the Coulomb interaction between the positively charged C atom of the carbonyl group and the AlCl3 fragment, which carries an excessive negative charge and which is not involved in donor-acceptor bonding with the carbonyl O atom. The IR spectra of the 1 : 1 and 1 : 2 complexes of benzophenone with AlBr3 were recorded, and the differences in the low-frequency regions of these spectra, which are indicative of the presence of the Br2Al-Br-AlBr3 fragment in the 1 : 2 complex, are discussed.

A simple method for quantitative estimation of C-H bond lengths in hydrocarbon radical cations

Abstract: A quantitative correlation between deviations of the C-H bond lengths of hydrocarbon molecules during their adiabatic single ionization and isotropic hyperfine coupling constants with protons of their primary radical cations (RC) was established. A simple method for estimation of the C-H bond lengths of hydrocarbon RC was proposed on the basis of the correlation found. Specific features of the structure of the RC of methane and severaln-alkanes of the general formula [H*(CH2nH*]+,n = 0 to 12, were analyzed. A widely used empirical rule, according to which deprotonation of hydrocarbon RC during the ion-molecular process is determined by the proton possessing the highest spin density, was refined and geometrically substantiated.

Odd‐hydrogen: An account on electronic structure, kinetics, and role of water in mediating reactions with atmospheric ozone. Just a catalyst or far beyond?

Abstract: Odd-hydrogen (any hydrogen-oxygen radical containing but a single hydrogen atom) plays a key role in atmospheric chemistry, particularly in the chemistry of ozone. Notable is also the role played by water in atmospheric and environmental chemistry. Without attempting a broad coverage, the present survey focuses on the electronic structure and dynamics of odd-hydrogen and related water-mediated complexes with impact in atmospheric chemistry, with emphasis on systems studied at the author's laboratory. Review oriented, it contains some ab initio results for HO3 and insights on hydrogen bonding and the role of water in mediating HOx reactions with ozone that have not appeared elsewhere. While providing an account on the status of the title topical issues, it is hoped that it may encourage new research directions. © 2013 Wiley Periodicals, Inc.

Structure and reactivity of vinylcyclopropane radical cation: Electron transfer photochemistry and ab initio calculations

Abstract: The electron-transfer photochemistry of vinylcyclopropane (1) generates three ring-opened products, 2−4, each bearing a methoxy as well as a 4-cyanophenyl group The products are ascribed to nucleophilic attack of methanol on the radical cation, 1•+ The attack is regioselective but not regiospecific; attack at the secondary cyclopropane carbons, leading to 2 and trans-3, is preferred; attack at the terminal vinylic carbon, yielding trans-4, occurs to a lesser extent The potential surface of 1•+ was probed by ab initio calculations; 1•+ has two minima, anti- and syn-1•+; both have Cs symmetry and belong to the unusual structure type with two lengthened cyclopropane bonds The calculations are in general agreement with the observed reaction pattern

The Vinylcyclopropane Radical Cation Rearrangement and Related Reactions on the C5H8•+ Hypersurface

Abstract: The structures and major reaction pathways of the vinylcyclopropane radical cation and several of its derivatives are studied using highly correlated QCISD(T) and hybrid density functional calculations. Three different reactions have been studied: (i) the stereoisomerization via acyclic intermediates, (ii) the [1,3] methylene shift to form the cyclopentene radical cation involving either a concerted or a stepwise pathway, and (iii) the [1,2] hydrogen shift leading to either 1,4-pentadiene or 1,3-pentadiene radical cations. The activation energies for these processes are found to be quite similar, making the different pathways competitive. At the QCISD(T)//QCISD level of theory, an activation energy of 21.6 kcal/mol was calculated for the concerted pathway of the radical cationic vinylcyclopropane rearrangement, with the stepwise pathway only 1.9 kcal/mol higher in energy. With the exception of a small overestimation of the stabilization of the acyclic intermediates by homoconjugation, the results from th...