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1

Spin trapping studies of essential oils in lipid systems

100%

Makarova K. , Drązikowska K. , Suska B. , Zawada K. , Wawer I.

Nukleonika

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2015

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tom Vol. 60, No. 3, part 1

461--468

EN

In the present work, we report the results of a spin trapping ESR study of four essential oils widely used for skin care products such as creams and bath salts. The studied essential oils are Rosmarini aetheroleum (rosemary), Menthae piperitae aetheroleum (mint), Lavandulae aetheroleum (lavender), and Thymi aetheroleum (thyme). Fenton reaction in the presence of ethanol was used to generate free radicals. The N-tert- -butyl-α-phenylnitrone (PBN) was used as a spin trap. In the Fenton reaction, the rosemary oil had the lowest effect on radical adduct formation as compared to the reference Fenton system. Since essential oils are known to be lipid soluble, we also conducted studies of essential oils in Fenton reaction in the presence of lipids. Two model lipids were used, namely 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-sn- -glycero-3-phosphocholine (DPPC). The obtained results suggested that in the presence of DOPC lipids, the •OH and PBN/•CHCH3(OH) radicals are formed in both phases, that is, water and lipids, and all the studied essential oils affected the Fenton reaction in a similar way. Whereas, in the DPPC system, the additional type of PBN/X (aN = 16.1 G, aH = 2.9 G) radical adduct was generated. DFT calculations of hyperfi ne splittings were performed at B3LYP/6-311+G(d,p)/EPR-II level of theory for the set of c-centered PBN adducts in order to identify PBN/X radical.

2

Crystal structures and conformers of CyMe4-BTBP

100%

Lyczko K. , Ostrowski S.

Nukleonika

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2015

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tom Vol. 60, No. 4, part 2

853--857

EN

The crystal structure of new conformation of the CyMe4-BTBP ligand (ttc) has been presented. The ttt conformer of this compound in a form of THF solvate has been also crystallized. The geometries of six possible conformations (ttt, ttc, tct, tcc, ctc and ccc) of the CyMe4-BTBP ligand have been modeled in the gas phase and in solutions (MeOH and H2O) by DFT calculations using B3LYP/6-31G(d,p) method. According to the calculations, in the three different media the conformers with trans orientation of the N atoms in the bipyridyl moiety are the most stable.

3

Crystal structures and conformers of CyMe4-BTBP

100%

Lyczko K. , Ostrowski S.

Nukleonika

|

2015

|

tom 60

|

nr 4

853-857

EN

The crystal structure of new conformation of the CyMe4-BTBP ligand (ttc) has been presented. The ttt conformer of this compound in a form of THF solvate has been also crystallized. The geometries of six possible conformations (ttt, ttc, tct, tcc, ctc and ccc) of the CyMe4-BTBP ligand have been modeled in the gas phase and in solutions (MeOH and H2O) by DFT calculations using B3LYP/6-31G(d,p) method. According to the calculations, in the three different media the conformers with trans orientation of the N atoms in the bipyridyl moiety are the most stable.

4

Spin trapping studies of essential oils in lipid systems

100%

Makarova K. , Drązikowska K. , Suska B. , Zawada K. , Wawer I.

Nukleonika

|

2015

|

tom 60

|

nr 3

461-468

EN

In the present work, we report the results of a spin trapping ESR study of four essential oils widely used for skin care products such as creams and bath salts. The studied essential oils are Rosmarini aetheroleum (rosemary), Menthae piperitae aetheroleum (mint), Lavandulae aetheroleum (lavender), and Thymi aetheroleum (thyme). Fenton reaction in the presence of ethanol was used to generate free radicals. The N-tert-butyl-α-phenylnitrone (PBN) was used as a spin trap. In the Fenton reaction, the rosemary oil had the lowest effect on radical adduct formation as compared to the reference Fenton system. Since essential oils are known to be lipid soluble, we also conducted studies of essential oils in Fenton reaction in the presence of lipids. Two model lipids were used, namely 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). The obtained results suggested that in the presence of DOPC lipids, the •OH and PBN/•CHCH3(OH) radicals are formed in both phases, that is, water and lipids, and all the studied essential oils affected the Fenton reaction in a similar way. Whereas, in the DPPC system, the additional type of PBN/X (aN = 16.1 G, aH = 2.9 G) radical adduct was generated. DFT calculations of hyperfine splittings were performed at B3LYP/6-311+G(d,p)/EPR-II level of theory for the set of c-centered PBN adducts in order to identify PBN/X radical.

5

Experimental and Density Functional Studies on Two Substituted 1H-Benzimidazoles

100%

Zhao P. , Yu H. , Jian F. , Wang X.

Polish Journal of Chemistry

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2007

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tom Vol. 81, nr 8

1511-1519

EN

Two substituted 1H-benzimidazoles, 2-(4-chlorophenyl)-1H-benzimidazole and 1-(2- chlorobenzyl)-2-(2-chlorophenyl)-1H-benzimidazole, have been synthesized and characterized by elemental analysis, IR and UV-Vis spectra. An extended MO calculations using density functional theory (DFT) at B3LYP/6-311G** level have been carried out on the two compounds. Comparison of the experiments with the calculated results suggests that the optimized geometries can well reproduce the molecular structures. Atomic charge distributions show that both of the title compounds are potential ligands to coordinate with metallic ions. Natural population analyses indicate that the electronic transitions corresponding to electronic spectra are mainly derived from the contribution of bands pi--pi*. Thermodynamic properties of the two title compounds at different temperatures have also been calculated on the basis of vibration analyses.

6

Influence of Substituents on Carbon-carbon Coupling Constants in Substituted Acetylenes

100%

Biedrzycka Z. , Kamieńska-Trela K.

Polish Journal of Chemistry

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2003

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tom Vol. 77 / nr 11

1637-1648

EN

Indirect spin-spin carbon-carbon coupling constants across a triple bond have been calculated using the DFT method in a large series of substituted acetylenes and compared with those determined experimentally. The DFTcalculated coupling data not only follow the trends observed for the experimental results but also the absolute 1JCC values are very well reproduced (in most cases within several Hz). It has been found that the magnitude of the coupling is strongly dependent on the electronegativity of the first atom of the substituent attached to the triple bond which is described by the equation: 1JXCCY (TOTAL) = 25.9 EXEY + 5.4. The smallest 1JCC coupling calculated for Li2C2 is 31.6 Hz and the largest one for C2F2 420.9 Hz, which reflects the dramatic changes occurring in the electronic structure of the triple bond upon substitution. A rough linear correlation has been found between the ln 1JCC(DFT) and the DFT optimized bond lengths, rCC. Additionally, the couplings across one Csp3-Csp and Csp2(arom)-Csp single bonds and those across two Csp3-CC and Csp2(arom)CC bonds have been derived and discussed.

7

DFT investigation on mechanism of dirhodium tetracarboxylate-catalyzed O-H insertion of diazo compounds with H2O

100%

Liu Z. , Liu J.

Open Chemistry

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2010

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tom 8

|

nr 1

223-228

EN

The mechanism of the dirhodium tetracarboxylate-catalyzed O-H insertion reaction of diazomethane and methyl diazoacetate with H2O has been studied in detail using DFT calculations. The rhodium catalyst and a diazo compound couple to form a rhodiumcarbene complex. Of two reaction pathways of the Rh(II)-carbene complex with H2O, the stepwise pathway is more preferable than the concerted one. Formation of a Rh(II) complex-associated oxonium ylide is an exothermal process, and direct decomposition of the ylide gives a very high barrier. The high barriers for the 1,2-H shift of Rh(II) complex-associated oxonium ylides make the ylides become stable intermediates in both reactions, especially for the reactions in solution. Difficulty in formation of a free oxonium ylide supports experimental results, indicating that the Rh(II) complex-catalyzed nucleophilic addition of a diazo compound proceeds via a Rh(II) complex-associated oxonium ylide rather than via a free oxonium ylide. [...]

8

Assembly of Protonated Tetramethylpyrazine (TMP) in Triiodide. Vibrational Spectra and DFT Simulations

100%

Sobczyk L. , Bator G. , Sawka-Dobrowolska W. , Nowicka-Scheibe J. , Grech E. , Pawlukojć A.

Polish Journal of Chemistry

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2009

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tom Vol. 83, nr 5

957-963

EN

In the complex of tetramethylpyrazine (TMP) with HI3 two protonated molecules of TMP form the assembly of composition (TMP×H+)2TMP(I3 - )2. The X-ray structure, determined at 100 K, shows the +N-H×××N hydrogen bonds markedly shorter than those found previously [13] at room temperature (2.828 ni s. 2.894 A). The DFT calculations for isolated cation yield the value of 3.038 capital A, ring that reflects the soft ness of the hydroen bond potential. The calculations of vibrational frequencies for crystalline state reflect very well the IR spectra. This relates particularly to the ni (NH+) mode. A remark able discrepancy is observed when calculations are performed for isolated assemblies.

9

Structure, conformation and hydrogen bonding of two amino-cycloalkanespiro-5-hydantoins

100%

Todorov P. , Petrova R. , Naydenova E. , Shivachev B.

Open Chemistry

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2009

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tom 7

|

nr 1

14-19

EN

The crystal structures of 3-amino-cycloheptanespiro-4′-imidazolidine-2′,5′-dione (I) {systematic name: 3-amino-1,3-diazaspiro[4.6] undecane-2,4-dione} and 3-amino-cyclooctanespiro-4′-imidazolidine-2′,5′-dione (II) {systematic name: 3-amino-1,3-diazaspiro[4.7] dodecane-2,4-dione}, have been determined. In both compounds the polar hydantoin groups cause molecules to aggregate via N-H...O and N-H...N interactions, forming a layer structure, in which the cycloalkane rings project outwards from the central, more polar, region. The observed molecular structure is compared with that calculated by density functional theory methods. [...]

10

A theoretical study of the neutral and the double-charged cation of cyclo[8]pyrrole and its interaction with inorganic anions

100%

Alkorta I. , Blanco F. , Elguero J.

Open Chemistry

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2009

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tom 7

|

nr 4

683-689

EN

A theoretical study of the complexation of cyclo[8]pyrrole dication, 2, and the corresponding system in neutral form, 3, with six anionic molecules has been carried out up to the B3LYP/6–311++G(2d,2p) computational level. The effect of the water solvation has been taken into account by means of the PCM method. The gas phase results correspond to the very large interaction energies expected for the interaction of molecules of opposite charge. In all the complexes, the analysis of the electron density by means of the Atoms In Molecules (AIM) methodology shows the presence of eight intermolecular interactions between the individual molecules. The results, using the water solvent model, indicate that the 2:SO42− complex is more stable than the 2:NO3−, in agreement with experimental results. [...]

11

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

88%

Kaczmarzyk T. , Rutkowska I. , Dziliński K.

Nukleonika

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2015

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tom 60

|

nr 1

51-55

EN

Molecular and electronic structure changes during successive reduction of a Fe-tetraphenylporphyrin chloride [Fe(III)(TPP):Cl] complex are reported on the basis of Mössbauer spectroscopy and DFT calculations. It is established that the attachment of additional electrons to a neutral Fe(III)(TPP):Cl molecule leads to significant shortening of Fe-N distances at the first stage of the reduction Fe(III)(TPP):Cl → Fe(II)(TPP) and lengthening of these bonds at the second stage Fe(II)(TPP) → Fe(I)(TPP). Changes of other bond lengths of the porphyrin ring also appear but in less degree. Interaction of Fe(II) and Fe(I)(TPP) with tetrahydrofuran (THF) solvent is considered. Electron configuration of Fe(II)(TPP) corresponds to intermediate-spin (S = 1) state and in the case of Fe(I)(TPP) low-spin state (S = ½) is observed. Electron density distribution in Fe(II)- and Fe(I)(TPP) complexes, in association with Mössbauer data, is analyzed. Good correlation between experimental and theoretical results was obtained.

12

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

88%

Kaczmarzyk T. , Rutkowska I. , Dziliński K.

Nukleonika

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2015

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tom Vol. 60, No. 1

51--55

EN

Molecular and electronic structure changes during successive reduction of a Fe-tetraphenylporphyrin chloride [Fe(III)(TPP):Cl] complex are reported on the basis of Mössbauer spectroscopy and DFT calculations. It is established that the attachment of additional electrons to a neutral Fe(III)(TPP):Cl molecule leads to signifi cant shortening of Fe-N distances at the fi rst stage of the reduction Fe(III)(TPP):Cl →Fe(II)(TPP) and lengthening of these bonds at the second stage Fe(II)(TPP)→Fe(I)(TPP). Changes of other bond lengths of the porphyrin ring also appear but in less degree. Interaction of Fe(II) and Fe(I)(TPP) with tetrahydrofuran (THF) solvent is considered. Electron configuration of Fe(II)(TPP) corresponds to intermediate-spin (S = 1) state and in the case of Fe(I)(TPP) low-spin state (S = ½) is observed. Electron density distribution in Fe(II)- and Fe(I)(TPP) complexes, in association with Mössbauer data, is analyzed. Good correlation between experimental and theoretical results was obtained.

13

One-bond C-H Coupling Constants of Acetyl Groups as Possible Monitors of CH Hydrogen Bonds and Electric Field Effects

88%

Hansen P.

Polish Journal of Chemistry

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2003

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tom Vol. 77 / nr 11

1683-1691

EN

C-H coupling constants of acetyl groups of a series of substituted 2-hydroxyacetophenones have been measured. These 1J(C,H) couplings are then intercompared and compared to acetophenone in order to elucidate the cause of the variation. Structures are calculated using ab initio DFT methods. A comparison of 2-hydroxyacetophenone and acetophenone shows an increase of ~0.5 Hz. An OR group in the 6-position of 2-hydroxyacetophenone leads to an increase of 1J(C,H) of ~1 Hz and substitution of an acetyl group at 3- or 5-positons likewise leads to an increase, whereas OR groups in 3-, 4- or 5-positions lead to small negative changes compared to the corresponding 2-hydroxyacetophenones. The variations in the 1J(C,H) coupling constants of 6-OR substituted 2-hydroxyacetophenones are discussed as a function of C-H hydrogen bonding and electric field effects. The former is shown not to be at play, whereas the latter is clearly active, but in some instances in an indirect fashion.

14

Hydrogen Bonds in the 1:1 and 2:1 Complexes of 1-Methylquinolinium-3-carboxylate with Mineral Acids Studied by NMR, FTIR and Raman Spectra and DFT Calculations

88%

Barczyński P. , Szafran M.

Polish Journal of Chemistry

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2009

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tom Vol. 83, nr 5

1061-1074

EN

The 1:1 and 2:1 complexes of 1-methylquinolinium-3-carboxylate (benzotrigonelline), 3QB, with HCl, HBr, HNO3, HClO4 and HBF4 have been synthesized and their FTIR, Raman, 1H and 13C NMR spectra have been analyzed. The 1:1 complexes with HCl and HBr crystallize as monohydrates and water molecule is localized between the betaine and counter-ions (Cl– and Br–). In the complexes with HNO3, HClO4 and HBF4 the anions are connected with the protonated 3QB via O–HźźźX– hydrogen bonds. The 2:1 complexes with HCl, HBr, HNO3 and HClO4 crystallize with one water molecule while with HBF4 as an hydrous. Their FTIR spectra show a broad and intense absorption in the 1500–400 cm–1 region, typical of hydrogen bonds shorter than 2.5 A. The water molecule in the 2:1 complexes, except perchlorate, forms hydrogen bonds with anions. The influence of counter-ions on proton and carbon-13 chemical shifts is very small and comparable with the experimental error. The protonation of 3QB causes deshielding of all protons and most carbons, except C-3, C-9 and COO, which are shielded. The 2:1 complexes in D2O dissociate to the 1:1 complexes and 3QB. Five 1:1 (2–6) and six 2:1 (7–12) complexes have been analyzed by the B3LYP/6-31G(d,p) calculations in order to determine the influence of conformation of COOH groups on hydrogen bond and homoconjugation.

15

UV Photoelectron Spectroscopy Studies of the Diazaxylylenes Generated from Amino(hydroxymethyl)pyridines

88%

Chrostowska A. , Sotiropoulos J. , Pfister-Guillouzo G. , Wojciechowski K.

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tom Vol. 77 / nr 5

535-545

EN

Diazaxylylenes generated by 1,4-elimination of water from amino(hydroxymethyl)pyridines under flash vacuum thermolysis (FVT) conditions can be directly studied by the UV-photoelectron spectroscopy (UV-PES). The elimination of water from these compounds starts at 450_C and is completed at 500-550_C. The interpretation of UV-photoelectron spectra was supported by Density Functional Theory studies

16

Low-energy electron transmission for the analysis of the interface barrier formation and the density of the unoccupied electronic states in the ultra-thin layers of fluorinated copper-phthalocyanine

88%

Komolov A. S. , Lazneva E. F. , Akhremtchik S. N. , Gerasimova N. B. , Pshenichnyuk S. A.

Organic Photonics and Photovoltaics

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2015

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tom 3

|

nr 1

EN

The interfacial structure made from the thermally deposited 5 – 7 nm thick layers of hexadecafluoro copper phthalocyanine (F16-CuPc) and of the unsubstituted copper phthalocyanine (CuPc) was subjected to the studies. The surface work function and the density of the unoccupied electron states (DOUS) located 5- 20 eV above the Fermi level (EF) were investigated during the CuPc/F16-CuPc interface formation using the very low energy electron diffraction (VLEED) method and the total current spectroscopy (TCS) measurement scheme. The DOUS peak structure of the organic films studied obtained from the TCS results showed a good correspondence to the main π* and σ* DOUS bands obtained from the density functional theory (DFT) calculations. The interfacial barrier was characterized by the negative charge transfer from the CuPc overlayer to the F16-CuPc underlayer occurred within the 5 nm thick interfacial region in the CuPc overlayer which was accompanied by the decrease of the surface work function from 4.9±0.1 eV to 4.3±0.1 eV. The stabilization of the π* DOUS bands, as well as restructuring of the low lying σ* bands was observed in the in the case of the fluorinated film (F16- CuPc) compared to the case of the unsubstituted CuPc film.

17

Protein thermal stabilization in aqueous solutions of osmolytes

88%

Bruździak P. , Panuszko A. , Jourdan M. , Stangret J.

Acta Biochimica Polonica

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2016

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tom 63

|

nr 1

65-70

EN

Proteins' thermal stabilization is a significant problem in various biomedical, biotechnological, and technological applications. We investigated thermal stability of hen egg white lysozyme in aqueous solutions of the following stabilizing osmolytes: Glycine (GLY), N-methylglycine (NMG), N,N-dimethylglycine (DMG), N,N,N-trimethylglycine (TMG), and trimethyl-N-oxide (TMAO). Results of CD-UV spectroscopic investigation were compared with FTIR hydration studies' results. Selected osmolytes increased lysozyme's thermal stability in the following order: Gly>NMG>TMAO≈DMG>TMG. Theoretical calculations (DFT) showed clearly that osmolytes' amino group protons and water molecules interacting with them played a distinctive role in protein thermal stabilization. The results brought us a step closer to the exact mechanism of protein stabilization by osmolytes.

18

The reaction mechanism of the [2+3] cycloaddition between α-phenylnitroethene and (Z)-C,N-diphenylnitrone in the light of a B3LYP/6-31G(d) computational study

88%

Jasiński R. , Mikulska M. , Barański A.

Open Chemistry

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2013

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tom 11

|

nr 3

404-412

EN

Abstract The analysis of reactivity indices suggests the polar nature of the [2+3] cycloaddition of a-phenylnitroethene to (Z)-C,N-diphenylnitrone. Similar conclusions can be drawn from the investigation of the reaction pathways using the B3LYP/6-31g(d) algorithm. This shows that the cycloaddition mechanism depends on the polarity of the reaction medium. A one-step mechanism is followed in the gas phase and toluene in all the theoretically possible pathways. In more polar media (nitromethane, water), a zwitterionic, two-step rather than a one-step mechanism occurs in the pathway leading to 3,4-trans-2,3,5-triphenyl-4-nitroisoxazolidine. Graphical abstract [...]

19

Structure-activity of chelating depressants for chalcopyrite/pyrite separation: DFT study and flotation experiment

88%

Li M. , Lian D. , Zhao F. , Tong X. , Wu C. , Gao X.

Physicochemical Problems of Mineral Processing

|

2021

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tom Vol. 57, iss. 6

102--112

EN

Three types of chelating depressants were studied for chalcopyrite/pyrite separation, including S-S, S-O, and O-O types, via density functional theory calculations and microflotation. The calculation results indicate that the depressant’s chelating atoms have large coefficient and great activity according to the molecular frontier orbital (HOMO and LUMO) and the orbital coefficients. For S-S type of depressant, S atom in both keto or enol forms won’t affect their HOMO and LUMO patterns and the orbital contributions. For S-O type, the presence of N atom in the ring structure of a molecular will increase the reactivity of O-Cu while weak S-Cu. For O-O type, the electron supply capacity of benzene ring is higher than strain chain, and atom N in strain chain increased their electron supply capacity. The microflotation results basically confirmed the prediction based on the calculation. The simulation results demonstrate that the interaction of a depressant with metals and minerals are affected obviously by the spatial structure and electronic structure of an atom in its molecular.

20

An experimental and theoretical study of the polar [2+3] cycloaddition reactions between 1-chloro-1-nitroethene and (Z)-C-aryl-N-phenylnitrones

88%

Jasiński R. , Mikulska M. , Barański A.

Open Chemistry

|

2013

|

tom 11

|

nr 9

1471-1480

EN

Abstract Kinetic studies and B3LYP/6-31g(d) calculations indicate the polar nature of [2+3] cycloadditions between 1-chloro-1-nitroethene to (Z)-C-aryl-N-phenylnitrones. This is clearly confirmed by the activation parameters and the substituent and solvent effects. Graphical abstract [...]