Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXXV.1 Solvation Effects on the Activation Parameters of Heterolysis of 1-Bromo-1-methylcyclopentane and 1-Bromo-1-methylcyclohexane. Correlation Analysis of Solvation Effects

Kinetics of heterolysis of 1-bromo-1-methylcyclopentane and -cyclohexane in protic and aprotic solvents were studied. Correlation analysis of the effect of solvent parameters on G , H , and S was performed.     

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

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] (E1 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.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXXII.1 Solvent Effects on Activation Parameters of Heterolysis of 1-Chloro-1-methylcyclopentane. Correlation Analysis of Solvation Effects

Kinetics of heterolysis of 1-chloro-1-methylcyclopentane in MeOH, BuOH, cyclohexane, i-PrOH, t-BuOH, tert-C₅H₁₁OH, -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 CF₃CH₂OH) and 8 aprotic solvents together and separately in either group of solvents was performed. In all the solvents studied, two H -S compensation effects were revealed.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXX.1 Correlation Analysis of Solvation Effects in Heterolysis of tert-Butyl Chloride

Quantitative analysis of the effect of solvent parameters on the rate of heterolysis of tert-butyl chloride was performed; the reaction rate is fairly described by the polarity, polarizability, and electrophilicity parameters or by the ionizing ability parameter, while the nucleophilicity of the solvent has no rate effect. A negative effect of nucleophilic solvation was revealed in protic solvents.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXXI. Solvent Effect on the Rate of 1-Methyl-1-chlorocyclopentane Heterolysis. Correlation Analysis of Solvation Effects

Heterolysis of 1-methyl-1-chlorocyclopentane in protic and aprotic solvents occurs by the E1 mechanism. The reaction rate in aprotic solvents or in a set of protic and aprotic solvents is satisfactorily described by the parameters of the polarity and electrophilicity or ionizing power of the solvents. In protic solvents, the reaction rate grows with increasing polarity or ionizing power of the solvent and decreases with increasing nucleophilicity.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXXVI.1 Solvent Effect on the Activation Parameters of Heterolysis of 1-Methyl-1-chlorocyclohexane. Correlation Analysis of Solvation Effects in Heterolysis of 1-Methyl-1-chlorocyclohexane and 1-Methyl-1-chlorocyclopentane

The kinetics of heterolysis of 1-methyl-1-chlorocyclohexane in six protic and eight aprotic solvents at 25-50°C was studied by the verdazyl method; v = k[RCl], E1 mechanism. The correlation analysis of the solvent effects on the activation free energy G , enthalpy H , and entropy S of heterolysis of 1-methyl-1-chlorocyclohexane and 1-methyl-1-chlorocyclopentane was performed for the same sets of solvents.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXXVII.1 Effect of Nucleofuge and Solvent of the Relative Rates of Heterolysis of 1-Halo-1-methylcyclopentanes and 1-Halo-1-methylcyclohexanes. Correlation Analysis of Solvation Effects

The effect of solvent ionizing ability on heterolysis rate enhances in the series 1-chloro-1-methylcyclohexane < 1-bromo-1-methylcyclohexane 1-chloro-1-methylcyclopentane < 1-bromo-1-methyl- cyclopentane. The lower sensitivity of cyclohexyl substrates compared with cyclopentyl is determined by conformational effects. Bromides are more sensitive to solvent effects than chlorides because of the stronger polarizability of the C-Br bond.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXIX. Solvent Effects on the Activation Parameters of Heterolysis of tert-Butyl Chloride

The kinetics of heterolysis of t-BuCl in sulfolane, PhCN, PhNO₂, acetophenone, cyclohexanone, chloroform, and 1,2-dichloroethane at 30-50°C were studied by the verdazyl method. Quantitative analysis of the effect of solvent parameters on the G , H , S , and log k _{2 5} values for heterolysis of t-BuCl in a set of 15 protic and 16 aprotic solvents and separately in either group of solvents was performed. In the above set of solvents, three H -S compensation effects are observed, associated with jump changes in the potential energy of the reaction.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XLII. Effect of Aprotic Solvent on the Rate of 3-Methyl-3-chloro-1-butene Dehydrochlorination. Correlation Analysis of Solvation Effects

The kinetics of 3-methyl-3-chloro-1-butene dehydrochlorination in propylene carbonate, γ-butyrolactone, sulfolane, acetone, MeCN, PhNO₂, PhCN, PhCOMe, MeCOEt, cyclohexanone, o-dichlorobenzene, PhCl, PhBr, 1,2-dichloroethane, dioxane, and AcOEt were studied; v = k[C₅H₉Cl], E1 mechanism. The reaction rate is satisfactorily described by the parameters of the polarity, electrophilicity, and cohesion of the solvent; the solvent nucleophilicity and polarizability exert no effect on the reaction rate.     

Kinetics and Mechanism of Monomolecular Heterolysis of Cage-Like Compounds: XVIII. Solvent Effect on the Rate of Heterolysis of 3-Bromocyclohexene. Correlation Analysis of Solvation Effects

The kinetics of E1 dehydrobromination of 3-bromocyclohexene in 23 aprotic and 9 protic solvents were studied by the verdazyl technique. The reaction rate is described by the polarity, electrophilicity, and ionizing power parameters of the solvent. Nucleophilicity, polarizability, and cohesion parameters of the solvent do not affect the reaction rate. The effects of equilibrium and nonequilibrium solvation of the transition state are discussed.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XLI. Solvent Effect on the Rate of 3-Methyl-3-chloro-1-butene Solvolysis. Correlation Analysis of Solvation Effects and Role of Solvent Nucleophilicity

The kinetics of 3-methyl-3-chloro-1-butene solvolysis at 25°C in MeOH, EtOH, BuOH, i-BuOH, PentOH, 2-PrOH, 2-BuOH, HexOH, OctOH, t-BuOH, t-PentOH, cyclohexanol, and allyl alcohol was studied by the verdazyl method; v = k[C₅H₉Cl], SN1 + E1 mechanism. The reaction rate shows a satisfactory correlation with the parameter of the solvent ionizing power E _T and is independent of the solvent nucleophilicity.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XL. Nature of Salt Effects in Dehydrobromination of 3-Bromocyclohexene in γ-Butyrolactone. Role of Solvation Effects of Dipolar Aprotic Solvents

The influence of neutral salts on the rate of heterolysis of 3-bromocyclohexene at 31°C in γ-butyrolactone was studied by the verdazyl method; ν = k[C₆H₉Br], E1 mechanism. Additions of lithium picrate do not affect the reaction rate; those of LiClO₄ and Et₄NClO₄ increase it; and those of LiCl, Et₄NCl, and KNCS decelerate the reaction. The nature of salt and solvation effects in the heterolysis of 3-bromocyclohexene in γ-butyrolactone, MeCN, and PhNO₂ is discussed.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 6, 2005, pp. 937–944.Original Russian Text Copyright © 2005 by Ponomarev, Stambirskii, Dvorko.     

Kinetics and Mechanism of Unimolecular Heterolysis of Framework Compounds: XVII. Solvation Effects in Dehydrobromination of <Emphasis Type="Italic">tert</Emphasis>-Butyl Bromide, 1-Bromo-1-Methylcyclohexane,and 2-Bromo-2-methyladamantane in Dipolar Aprotic Solvents

Dehydrobromination rate of tert-butyl bromide, 1-bromo-1-methylcyclohexane, and 2-bromo-2-methyladamantane grows with increasing polarity and dipole moment of solvents. No correlation was found between rate constants of the process and electrophilicity or ionizing power of the solvents. The observed solvation effects are due mainly to dispersion interactions.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXVIII. Effect of the Nature of the Verdazyl Indicator on Salt Effects in Dehydrobromination of 3-Bromocyclohexene in Nitrobenzene

The salt effect on the rate of dehydrobromination of 3-bromocyclohexene in PhNO2 depends on the nature of the verdazyl indicator. With triphenylverdazyl and its chloro and nitro derivatives in the presence of Et₄NClO₄, a normal salt effect is observed, in the presence of bromides, a superposition of normal and special salt effects, while in the presence of chlorides, a superposition of normal and special negative salt effects. With the dimethoxy verdazyl derivative, a normal salt effect is always observed.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXXIX. Salt Effect of LiClO<Subscript>4</Subscript>in Heterolysis of Ph<Subscript>2</Subscript>CHCl in γ-Butyrolactone

Additions of LiClO₄ accelerate the heterolysis of Ph₂CHCl in γ-butyrolactone; v = k[Ph₂CHCl], SN1 mechanism. The salt effect increases with an increase in the electron-acceptor properties of the verdazyl indicator. A superposition of three salt effects (normal, special, and negative special) is observed.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 105–110.Original Russian Text Copyright © 2005 by Dvorko, Ponomareva, Golovko, Pervishko.     

Solvation and Conformational Effects in Heterolysis of 1-Methylcycloalkyl Halides

In the series of substrates 1-bromo-1-methylcyclopentane, 1-bromo-1-methylcyclohexane, 1-methyl-1-chlorocyclopentane, 1-methyl-1-chlorocyclohexane, the heterolysis rate in acetone at 25 °C is reduced by four orders of magnitude; v = k[RX], E1 mechanism. The decrease in reaction rate as we go from a cyclopentyl compound to a cyclohexyl compound is due to the decrease in entropy of activation as a result of rapid solvation of the transition state as the conformational barrier is overcome.     

Methane Pyrolysis Stimulated by Admixture of Atomic Hydrogen: 2. Mechanism Analysis and Kinetics Calculation

The kinetics of methane pyrolysis stimulated by the introduction of atomic hydrogen into the reaction medium from an arcjet plasma source was analyzed. Numerical simulation of the reaction kinetics demonstrated that the thermal pyrolysis at lower temperatures (1800 K or lower) followed the radical chain mechanism with short chains (a chain length of 2 or 3), and the addition of atomic hydrogen considerably increased the rate of the process. An analysis of the kinetics of pyrolysis in a stirred reactor showed that acetylene was formed immediately after methane degradation without the buildup of by-products in the reaction medium.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 4, 2005, pp. 312–316.Original Russian Text Copyright © 2005 by Baranov, Demkin, Zhivotov, Nikolaev, Rusanov, Fedotov.     

Photodissociation of Halonaphthalenes in Solution: Comparative Photochemistry of 1-Iodo-, 1-Bromo-, and 1-Chloronaphthalenes

Fluorescence measurements have been used to follow the build-up of photoproducts during the direct and benzophenone-sensitized irradiation of the title compounds 1-IN, 1-BrN, and 1-ClN (HN = naphthalene). Compounds 1-IN and 1-BrN react by homolytic dissociation through their lowest triplet and singlet excited states, respectively. Compound 1-ClN does not undergo C–Cl bond fission, except through electron transfer in the presence of an amine A, In the absence of this electron transfer, 1-ClN reacts only through substitution and oxidation processes.     

Kinetics and mechanism of unimolecular heterolysis of framework compounds: XX. Solvation and steric effects in heterolysis of 2-halo-2-alkyladamantanes in sulfolane and butanol

Hetrolysis rate of 2-halo-2-phenyladamantanes in BuOH is 1000 times higher than the heterolysis rate of 2-halo-2-methyladamantanes. The heterolysis rate in sulfolane does not depend on the substituent, but the phenyl group exhibits a negative steric effect.     

Solvation and solvatochromism in CO2-expanded liquids. 1. Simulations of the solvent systems CO2 + cyclohexane, acetonitrile, and methanol

Molecular dynamics simulations of CO(2)-expanded cyclohexane, acetonitrile, and methanol are reported at various compositions along the experimental bubble-point curve at 298 K. Simulated properties include energies, local compositions, viscosities, diffusion coefficients, and dielectric constants and relaxation times. On the basis of the limited comparisons to experimental data currently available, the results indicate that simple intermolecular potential models previously developed for simulating the pure components provide reasonable representations of the energetics and dynamics of these gas-expanded liquids.