頁籤選單縮合
題 名 | Solvolysis of 1-Aryl-1-tert-butylmethyl Bromides. Hammett-type Correlation Analysis and Revised Y Scale |
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作 者 | 劉廣定; 秦建譜; 俞德淦; 段葉芳; | 書刊名 | Journal of the Chinese Chemical Society |
卷 期 | 46:5 1999.10[民88.10] |
頁 次 | 頁789-796 |
分類號 | 341.34 |
關鍵詞 | 溶劑分解反應; Solvolysis; Hammett-type correlation analysis; Solvent effect; Y scale; |
語 文 | 英文(English) |
英文摘要 | The solvolysis of a series of 1-aryl-1-tert-butylmethyl bromides (1a-1g) in a variety of solvents were carried out. Linear relationships were observed from Hammett-type analysis of logarithm of rate constants using single-parameter Brown-Okamoto equation (Eqn. 1) and dual-parameter Yukawa-Tsuno equation (Eqn. 2), respectively. The ρ values and the γ values were found to depend mainly on the range of substituents and not the type of solvents employed. The observation of an upward deviation for the data points of strongly deactivating substrates 1f and 1g could be interpreted by an electrophilic acceleration owing to the solvation of leaving group. It is likely an additional example of overshadowed solvent effect in the dual-parameter treatment of rate data. Moreover, the variation of γ values was found contradicting the general consideration of resonance contribution. The observed excellent linear correlations with Y □ and the good solubility in aqueous solution with high percentage of water made 1c a better reference standard than 2-bromo-2-(4-trifluormethyl)adamantane(3) for obtaining revised and extended Y □ values. Correlation analysis using the single-parameter Grunwald-Winstein equation (Eqn. 3) with Y □ was found to be superior over the dual-parameter equation containing Y □ and I (Eqn. 5). |
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