Hydrogen Atom Reactivity toward Aqueous tert-Butyl Alcohol

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• 作者：Sergei V. Lymar ; Harold A. Schwarz
• 刊名：The Journal of Physical Chemistry A
• 出版年：2012
• 出版时间：February 9, 2012
• 年：2012
• 卷：116
• 期：5
• 页码：1383-1389
• 全文大小：382K
• 年卷期：v.116,no.5(February 9, 2012)
• ISSN：1520-5215

文摘

Through a combination of pulse radiolysis, purification, and analysis techniques, the rate constant for the H + (CH₃)₃COH 鈫?H₂ + ^{鈥?/sup>CH₂C(CH₃)₂OH reaction in aqueous solution is definitively determined to be (1.0 卤 0.15) 脳 105 M鈥? s鈥?, which is about half of the tabulated number and 10 times lower than the more recently suggested revision. Our value fits on the Polanyi-type, rate鈥揺nthalpy linear correlation ln(k/n) = (0.80 卤 0.05)螖H + (3.2 卤 0.8) that is found for the analogous reactions of other aqueous aliphatic alcohols with n equivalent abstractable H atoms. The existence of such a correlation and its large slope are interpreted as an indication of the mechanistic similarity of the H atom abstraction from 伪- and 尾-carbon atoms in alcohols occurring through the late, product-like transition state. tert-Butyl alcohol is commonly contaminated by much more reactive secondary and primary alcohols (2-propanol, 2-butanol, ethanol, and methanol), whose content can be sufficient for nearly quantitative scavenging of the H atoms, skewing the H atom reactivity pattern, and explaining the disparity of the literature data on the H + (CH₃)₃COH rate constant. The ubiquitous use of tert-butyl alcohol in pulse radiolysis for investigating H atom reactivity and the results of this work suggest that many other previously reported rate constants for the H atom, particularly the smaller ones, may be in jeopardy.}