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: XXXIII.1 Correlation Analysis of Solvation Effects in Monomolecular Heterolysis of 1-Bromo-1-methylcyclopentane, 1-Bromo-1-methylcyclohexane, and 2-Bromo-2-methyladamantane

The rate of heterolysis of 1-bromo-1-methylcyclopentane and 1-bromo-1-methylcyclohexane is determined by the equation v = k[RBr], mechanism E1. Comparative correlation analysis of solvation effects in heterolysis of these substrates and 2-brom-2-methyladamantane was performed.     

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: 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.     

Nature of solvation effects and mechanism of heterolysis of <Emphasis Type="Italic">tert</Emphasis>-alkyl halides

Specificities of heterolysis of tert-alkyl halides in protic and aprotic solvents were analyzed. Values of log k ₂₅ for heterolysis of tert-butyl chloride, tert-butyl bromide, tert-butyl iodiede, 1-chloro-1-methylcyclopentane, 1-chloro-1-methylcyclohexane, 1-bromo-1-methylcyclopentane, 1-bromo-1-methylcyclohexane, 2-chloro-2-phenylpropane, 1-iodoadamantane, and 2-bromo-2-methyladamantane in 19 to 44 solvents, determined mostly by the verdazyl technique were collected. Correlation analysis of solvation effects was performed in terms of multiparameter equations based on the linear free energy relationship principle, as well as in the logk-E _T coordinates. The nature of solvation effects and mechanism of heterolysis of a covalent C-Hlg bond were discussed.     

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 unimolecular heterolysis of cage-like compounds: XXI. Solvent effect on the realtive rate of heterolysis of 2-methyland 2-phenyl-2-haloadamantanes. Role of activation parameters

The kinetics of heterolysis of 2-chloro-2-methyladamantane, 2-bromo-2-methyladamantane, 2-chloro-2-phenyladamantane, and 2-bromo-2-phenyladamantane in isopropyl alcohol, tert-butyl alcohol, acetonitrile, nitromethane, cyclohexanone, and γ-butyrolactone were studied using the verdazyl technique. The rate constant ratio k _Ph/k _Me decreases from three orders of magnitude to unity in the solvent series BuOH > i-PrOH > t-BuOH > MeCN > PhNO₂ > cyclohexanone > γ-butyrolactone > sulfolane, which results from weakening of conjugation between the phenyl group and emerging carbocationic center. The effect of solvent on the entropy and enthalpy of heterolysis in going from 2-methyl-substituted 2-haloadamantanes to their 2-phenyl analogs is discussed.     

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 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.