The 4,4,4-Trifluoroacetoacetic Acid Keto−Enol System in Aqueous Solution. Generation of the Enol by Hydration of Trifluoroacetylketene
作者:Y. Chiang、A. J. Kresge、Q. Meng、Y. Morita、Y. Yamamoto
DOI:10.1021/ja991561x
日期:1999.9.1
Trifluoroacetylketene was generated in aqueous solution by flash photolysis of 2,2-dimethyl-6-trifluoromethyl-4H-1,3-dioxin-4-one and its spiro analogue, 4-trifluoromethyl-1,5-dioxaspiro[5.5]undec-3-en-2-one, and rates of hydration of the ketene to 4,4,4-trifluoroacetoacetic acid enol as well as subsequent ketonization of the enol were measured in this solvent across the acidity range [H+] = 10-1−10-12
通过 2,2-二甲基-6-三氟甲基-4H-1,3-二恶英-4-one 及其螺类似物 4-三氟甲基-1,5-二氧杂螺[5.5] 十一烷的闪光光解在水溶液中生成三氟乙酰乙烯酮在该溶剂中,在酸度范围 [H+] = 10-1− 内测量了 3-en-2-one 和乙烯酮水合为 4,4,4-三氟乙酰乙酸烯醇以及随后烯醇的酮化的速率10-12 M。对这些数据产生的速率曲线的分析提供了烯醇的羧酸基团的酸度常数 pQa,E = 1.85 和它的烯醇羟基基团的酸度常数 p = 9.95,这使得这些基团为 2 和 3 个数量级分别比母体未氟化乙酰乙酸烯醇中的相应基团酸性更强。还测量了 4,4,4-三氟乙酰乙酸的酮基的烯醇化率,