| 摘要: | The solvolysis of 2-bromo-2-methylpropane (1B), 2-bromo-2-methylbutane (2B), 2-bromo-2,3-dimethylbutane (3B), 2-bromo-2,3,3-trimethylbutane (4B), 3-bromo-3-methylpentane (5B), 3-bromo-2,3-dimethylpentane (6B), 3-bromo-2,2,3-trimethylpentane (7B), 3-bromo-3-ethylpentane (8B), 3-bromo-3-ethyl-2-methylpentane (9B) and 2-bromo-2,4,4-trimethylpentane (11B) in 15 to 21 solvents was studied, and correlation analyses by using the single- and dual-parameter Grunwald-Winstein equations (Eqns 1 and 2) were examined. Substrates 7B, 9B and 11B showed excellent linear relationship (R >= 0.997) in the logk - Y-Br plots and indicated limiting S(N)1 Mechanism for the solvolysis. On the other hand, bromides 1B-6B and 8B gave linear correlations (R = 0.987-0.996) with the dual-parameter (Y-Br and N-OTs) equation (2) only, which indicated the presence of significant nucleophilic solvent participation. Normal trends of reactivity due to the relief of B-strain could be found in the poorly nucleophilic trifluoroethanol. Similar to the corresponding chlorides, the overwhelming influence of nucleophilic solvent assistance results in the observed inverse order of reactivity: k(2B) > k(3B), k(5B) > k(6B) and k(8B) > k(9B). |
