Use of Hydrogen Isotope Effects to Identify the Attacking Nucleophile in the Enolization of Ketones Catalyzed by Acetic Acid1-3
Use of Hydrogen Isotope Effects to Identify the Attacking Nucleophile in the Enolization of Ketones Catalyzed by Acetic Acid1-3
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利用氢同位素效应识别乙酸催化酮烯醇化反应中的攻击亲核试剂1-3
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发表时间：
1958
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通讯作者：
L. J. Schaad
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作者：
C. G. Swain;E. C. Stivers;J. F. Reuwer;L. J. Schaad
乙酸对烯醇化的催化不是由于乙酸分子作用于酮氧和水分子从碳上除去质子，而是由于氢离子作用于酮氧和乙酸离子从碳上除去质子。在α-苯基异己苯酮的情况下（具有一个α氢的酮）在具有8.4 M二氧六环（72体积%二氧六环）的水溶液中的溶液。碳原子上的氚同位素效应的大小是亲核试剂攻击的特征，随着亲核试剂的碱性和反应性的增加而增加。对于乙酸的催化作用，它的值（11.4）对于水的亲核攻击来说太高，但对于乙酸根离子的攻击来说是正确的。给出了氚的关系式，并与实验数据进行了比较。（auth）
Catalysis of enolizaiion by acetic acid is nnt due to an acetic acid molecule acting on the ketonic oxygen and a water molecule removing the proton from carbon, but instead to hydrogen ion acting on the ketonic oxygen and acetaie ion removing the proton from carbon, in the case of alpha -phenylisocaprophenone (a ketone with one alpha hydrogen) in aqueous solution with 8.4 M dioxane (72% dioxane by volume) at 100 . The magnitude of the protium/tritium isotope effect at the carbcn is diagnostic of the attacking nucleophile, increasing as the basicity and reactivity of the nucleophile increases. For catalysis by acetic acid, it has a value (11.4) which is too high for nucleophilic attack by water, but correct for attack by acetate ion. A relation between tritium ived and compared with experimental data. (auth)