- Kinetics and mechanism of monomolecular heterolysis of commercial organohalogen compounds: XXXII. Solvent effects on activation parameters of heterolysis of 1-chloro-1-methylcyclopentane. Correlation analysis of solvation effects
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Kinetics of heterolysis of 1-chloro-1-methylcyclopentane in MeOH, BuOH, cyclohexane, i-PrOH, t-BuOH, tert-C5H11OH, γ-butyrolactone, MeCN, PhCN, PhNO2, acetone, PhCOMe, cyclohexanone, and 1,2-dichloroethane at 25-50°C were studied by the verdazyl method. Correlation analysis of solvent effects on activation parameters of the reaction in 8 protic (additionally, AcOH and CF 3CH2OH) and 8 aprotic solvents together and separately in either group of solvents was performed. In all the solvents studied, two ΔH≠-ΔS≠ compensation effects were revealed.
- Dvorko,Koshchii,Prokopets,Ponomareva
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- Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXXIV. Solvent Effect on the Heterolysis Rate of 1-Chloro-1-methylcyclohexane. Correlation Analysis of Solvation Effects in Heterolysis of 1-Chloro-1-methylcyclohexane and 1-Chloro-1-methylcyclopentane
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The kinetics of heterolysis of 1-chloro-1-methylcyclohexane in 9 protic and 25 aprotic solvents at 25°C were studied by the verdazyl method. The kinetic equation is v = k[RCl] (El mechanism). The heterolysis rate of 1-chloro-1-methylcyclohexane in protic solvents is two orders of magnitude lower than that of 1-chloro-1-methylcyclopentane, whereas in low-polarity and nonpolar aprotic solvents the rates are close. A correlation analysis was made to reveal the solvation effects in heterolysis of both chlorides in a set of 9 protic and 25 aprotic solvents, and separately in protic and aprotic solvents.
- Dvorko,Koshchii,Ponomareva
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- Triarylverdazyl radicals as promising redox-active components of rechargeable organic batteries
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A novel design of electroactive components of rechargeable organic batteries based on stable verdazyl radicals bearing various substituents is proposed. 3-Positioned aromatic substituents at the verdazyl moiety affect the reduction potentials and almost do not affect the oxidation potential, while 1-positioned aromatic substituents affect contrariwise the oxidation potential of this radical without any influence on the reduction potential. The acquired electrochemical data allowed us to reveal the structure—potential relationship for the cathodic and anodic processes, which provided the design of triarylverdazyl radicals possessing record-breaking parameters of the “electrochemical gap”.
- Burtasov, A. A.,Chernyaeva, O. Yu.,Kostryukov, S. G.,Kozlov, A. Sh.,Pryanichnikova, M. K.,Tanaseichuk, B. S.
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p. 1321 - 1328
(2020/09/07)
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- Kinetics and mechanism of monomolecular heterolysis of commercial organohalogen compounds: XLIII. Solvent effect on activation parameters of dehydrochlorination of 3-chloro-3-methylbut-1-ene. Correlation analysis of solvation effects
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The influence of temperature on the rate of dehydrochlorination of 3-chloro-3-methylbut-1-ene in 17 aprotic and 13 protic solvents, ν = k[C 5H9Cl], was studied by the verdazyl method. In aprotic solvents, the electrophilicity, ionizing power, and cohesion of solvents decrease ΔG ≠ by increasing ΔS ≠. The nucleophilicity and polarizability increase both ΔH ≠ and ΔS ≠ to equal extent and therefore do not affect ΔG ≠. In protic solvents, the solvent nucleophilicity increases ΔH ≠ to a greater extent than ΔS ≠, and the overall effect of the nucleophilic solvation is small and negative.
- Ponomarev,Zaliznyi,Dvorko
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p. 1204 - 1214
(2008/02/12)
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- Kinetics and mechanism of monomolecular heterolysis of commercial halogenated organic compounds: XXVI. Correlation analysis of solvation effects in dehydrobromination of 1-bromo-1-methylcyclohexane and tert-butyl bromide
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The dehydrobromination rate of 1-bromo-1-methylcyclohexane and tert-butyl bromide increases with increasing polarity, electrophilicity, and cohesiveness of a solvent, and decreases with increasing solvent nucleophilicity and polarizability; a negative effect of nucleophilic solvation is observed.
- Dvorko,Vasil'kevich,Ponomareva,Koshchii
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p. 724 - 731
(2007/10/03)
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- A direct one-step preparation of triarylverdazylium salts from the corresponding triarylformazans
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6-(4-Substituted-phenyl)-2,4-diphenylverdazylium salts 2 (8 examples, 55-93%) were prepared by the reaction of 3-(4-substituted-phenyl)-1,5-diphenylformazans 1 with formaldehyde and different organic and inorganic acids in a two-phase chloroform/water med
- Katritzky, Alan R.,Belyakov, Sergei A.
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- Comparison of Spectroscopic and Electrochemical Studies of Disproportionation Equilibria of 1,3,5-Triphenylverdazyl Radical in DMF Containing Carboxylic Acids
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Stoichiometry and equilibrium constants for the disproportionation of the title radicals in N,N-dimethylformamide containing salicilic, chloroacetic, and phenylacetic acids were determined on the basis of absorption spectra.On the other hand, only apparent equilibrium constants depending on concentrations of an acid and a radical could be obtained from electrochemical measurements at a mercury electrode.Significant differences in reaction stoichiometry and in order of magnitudes of disproportionation constants found under spectroscopic and electrochemical conditionswere discussed in terms of an influence of the electric field in the double layer on the distribution of different associates formed by verdazyl species with acids.Keywords: Disproportionation equilibrium; Effect of the electrode field.
- Jaworski, Jan S.,Krawczyk, Irena
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- DISSOCIATION ENERGY OF THE N-H BOND IN 2,6-DIARYL-4-PHENYL-1,2,3,4-TETRAHYDRO-SYM-TETRAZINES AND THE COMPARATIVE REACTIVITY OF SYM-TETRAZINYLS IN DEHYDROGENATION OF HYDRAZOBENZENE
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The equilibrium constants in the reactions of 2,6-diaryl-4-phenyl-1,2,3,4-tetrahydro-sym-tetrazines with 2,2,6,6-tetramethyl-4-oxopiperidin-1-oxyl in heptane were determined by spectrophotometric and ESR methods.The dissociation energies of the N-H bond is the sym-tetrazines were determined.Results are given which indicate that the substituents in the phenyl ring at the C6 and N2 atoms have effects substantially different and opposite in sign on the thermochemical value of the dissociation energy of the N-H bond in sym-tetrazines.The sym-tetrazines with donatingsubstituents at the C6 atom and accepting substituents at the nitrogen atom are characterized by the largest dissociation energy for the N-H bond.The kinetics of the dehydrogenation of hydrazobenzene by sym-tetrazinyls in acetonitrile were investigated.It was found that there is an inverse relationship between the activation energies of the reaction and the dissociation energy of N-H bond in sym-tetrazines.The reaction mechanism is discused.
- Misyura, A. V.,Polumbrik, O. M.,Markovskii, L. N.
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p. 381 - 387
(2007/10/02)
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- KINETICS AND MECHANISM OF MONOMOLECULAR HETEROLYSIS OF FRAMEWORK COMPOUNS. VI. DEHYDROBROMINATION OF 2-BROMO-2-METHYLADAMANTANE IN ACETONITRILE
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The kinetics of the dehydrobromination of 2-bromo-2-methyladamantane in acetonitrile were studied in the presence of triphenylverdazyl as internal indicator; k25 = 8.57E-5 sec-1, ΔH% 79 kJ/mole, ΔS% -58 kJ/mole°Additions of water, phenols ,lithium perchlorate, and bromides increase the reaction rate, and additions of nitrates and picrates reduce it.A similar pattern is observed in the dehydrobromination of tert-butyl bromide in acetonitrile.In the presence of tetraethylammonium chloride the heterolysis rate of 2-bromo-2-methyladamantane decreases, while that of tert-butyl bromide increases.The positive salt effect is explained by stabilization of the transition state by the salt, and the negative salt effect is explained by the reaction of the anion with the sterically separated or solvent-separated ion pair of the substrate.
- Ponomareva, E. A.,Vasil'kevich, A. I.,Tarasenko, P. V.,Dvorko, G. F.
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p. 490 - 497
(2007/10/02)
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- FREE RADICALS. XXIV. REACTION OF TRIPHENYLVERDAZYL WITH CH ACIDS
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Triphenylverdazyl is capable of dehydrogenating β-dicarbonyl compounds with a high content of the enolic form.The rate of this reaction is described by a third-order equation (second in the radical and first in the CH acid).
- Tanaseichuk, B. S.,Belozerov, A. I.,Pryanichnikova, M. K.,Butin, K. P.
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p. 1480 - 1484
(2007/10/02)
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- REACTIVITY OF PERFLUOROPHENYL-CONTAINING VERDAZYLS. II. DEHYDROGENATION OF THIOPHENOL
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The kinetics of the dehydrogenation of thiophenol by perfluorophenyl-containing verdazyls in acetonitrile were studied by UV and ESR spectroscopy.The reaction rate depends substantially on the position and the number of perfluorophenyl substituents in the radical.The dependence of the activation energies on the thermal effects of the reactions is described by the Polanyi-Semenov equation.
- Polumbrik, O. M.,Ryabokon', I. G.
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p. 1809 - 1813
(2007/10/02)
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- KINETICS AND MECHANISM OF MONOMOLECULAR HETEROLYSIS OF FRAMEWORK COMPOUNDS. I. IONIZATION OF 1-ADAMANTYL p-TOLUENESULFONATE IN ACETONITRILE
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The heterolysis of 1-adamantyl p-toluenesulfonate in acetonitrile was investigated preparatively and kinetically (in the presence of triphenylverdazyl as internal indicator) ( v = k, k25 = 1.97E-6 sec-1, ΔH = 88.8 kJ/mole, ΔS25 = -57.3 J/mole*deg).Additions of tetraethylammonium bromide, tetraethylammonium perchlorate, tetraethylammonium p-toluenesulfonate, and N-butylquinolinium p-toluenesulfonate ( 0.05 - 0.005 M ) do not affect the reaction rate, and the normal salt effect and the effect of the law of mass action do not appear.The reaction rate is increased a little by the addition of water and phenol, and is increased greatly by the addition of sodium perchlorate, lithium perchlorate, and lithium bromide.The salt effect increases with decrease in the size of the cation ( electrophilic catalysis ).The addition of the cation was confirmed by additions of dibenzo-18-crown-6.It is suggested that the controlling stage of the reaction involves conversion of an intimate ion pair of the substrate into a solvent-separated ion pair.
- Ponomareva, E. A.,Tarasenko, P. V.,Yurchenko, A. G.,Dvorko, G. F.
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p. 481 - 493
(2007/10/02)
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- REACTIVITY OF PERFLUOROPHENYL-CONTAINING VERDAZYLS. I. DEHYDROGENATION OF HYDRAZOBENZENE
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The kinetics of the dehydrogenation of hydrazobenzene by perfluorophenyl-containing verdazyls in dioxane, benzene, and acetonitrile was investigated by electronic and ESR spectroscopy.The reaction rate is described by a second-order kinetic equation and d
- Polumbrik, O.M.,Ryabokon', I.G.,Markovskii, L.N.
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p. 917 - 921
(2007/10/02)
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