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 |
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Authors: | G F Dvorko A I Vasil’kevich I V Koshchii K V Mikhal’chuk |
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Institution: | 1.“Kiev Polytechnical Institute” Ukrainian National Technical University,Kiev,Ukraine |
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Abstract: | 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. |
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Keywords: | |
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