Flash Photolysis of 2,2,6-Trimethyl-4<i>H</i>-1,3-dioxin-4-one in Aqueous Solution: Hydration of Acetylketene and Ketonization of Acetoacetic Acid Enol
作者:Y. Chiang、H.-X. Guo、A. J. Kresge、O. S. Tee
DOI:10.1021/ja9540435
日期:1996.1.1
subsequent ketonization of the enol were measured in this solvent across the acidity range [H+] = 1−10-13 M. Acetylketene proved to be a remarkably reactive substance, undergoing uncatalyzed hydration with the rate constant k = 1.5 × 106 s-1, some 104 times more rapidly than ketene itself; the acetylketene hydration reaction was also catalyzed weakly by hydroxide ion but not by hydrogen ion. Ketonization
乙酰乙烯酮是通过 2,2,6-三甲基-4H-1,3-二恶英-4-one 在水溶液中的闪光光解产生的,并且乙烯酮水合为乙酰乙酸烯醇和随后烯醇酮化的速率在这种溶剂的酸度范围 [H+] = 1-10-13 M。 乙炔被证明是一种非常活泼的物质,以速率常数 k = 1.5 × 106 s-1 进行未催化的水合,比乙烯酮本身快约 104 倍; 乙酰乙烯酮水合反应也被氢氧根离子弱催化,但不被氢离子催化。乙酰乙酸烯醇的酮化速度在毫秒到秒范围内要慢得多。该反应显示出复杂的速率曲线,可以解释为酸性区域中烯醇的羧酸根离子化形式的速率决定碳质子化和碱性区域中双离子化羧酸根-烯醇化物形式的速率决定碳质子化. 数据分析提供了酸度常数 pQa = 4.05...