作者:David S. Shipley、Angela M. Ross、Ram S. Mohan、Dale L. Whalen、Jane M. Sayer、Paul M. Serve、Donald M. Jerina
DOI:10.1021/jo00084a012
日期:1994.3
(4-Nitrophenoxy)ethylene oxide (1a) (2-chloro-4-nitrophenoxy)ethylene oxide (1b), and (4-phenylphenoxy) ethylene oxide (1c) were synthesized. Rates of acid-catalyzed, noncatalyzed, and hydroxide ion-catalyzed reactions for is and Ib and rates of acid-catalyzed and noncatalyzed hydrolysis of 1c were measured in 0.1 M NaClO4 solutions. Acid-catalyzed hydrolysis of 1a is ca. 6200 times faster than that of 4-nitrostyrene oxide, and that of 1c is 57 times faster than that of styrene oxide. These increased rates are attributed to stabilization of developing positive charge on the acetal carbon by the phenoxy oxygen that is present in the substituted phenoxyethylene oxides but not in the styrene oxides. The pH-rate profiles for reaction of 1a and 1b in 1.0 M KCl solutions over the pH range 2-14 were determined. At intermediate pH, the rates of reaction of 1a and 1b in 1.0 M KCl solutions are ca. 6-8 times faster than the corresponding rates in 0.1 M NaClO4 solutions. From rate and product studies, these increased reaction rates in KCl solutions were attributed to bimolecular attack of chloride ion at the methylene carbon of the epoxide moiety, The reactivity of 1a is greater than that of 1b toward acid-catalyzed hydrolysis but less than that of 1b in both noncatalyzed and hydroxide ion-catalyzed hydrolysis. Compound 1c reacts about 73-fold faster than 1a in acid and about 11-fold faster in the noncatalyzed reaction. From reactivity considerations, it is proposed that H2O and HO- also add as nucleophiles to the methylene carbon of the epoxide moieties of 1a and 1b, whereas H2O adds to the acetal carbon of 1c.
(4-硝基苯氧基)环氧乙烷(1a)、(2-氯-4-硝基苯氧基)环氧乙烷(1b)以及(4-苯基苯氧基)环氧乙烷(1c)被合成出来。在0.1 M NaClO4溶液中,测定了1a和1b在酸催化、无催化和氢氧化物离子催化条件下的反应速率,以及1c在酸催化和无催化条件下的水解速率。酸催化下,1a的水解速率比4-硝基邻苯二甲酰乙烷快约6200倍,1c的水解速率比苯基乙基砜快57倍。这些增加的速率归因于在取代的苯氧基环氧乙烷中存在、但在苯基乙基砜中不存在的苯氧基氧对乙酰碳上正在形成的正电荷的稳定作用。
在pH范围为2-14的1.0 M KCl溶液中,测定了1a和1b的pH-速率曲线。在中等pH下,1a和1b在1.0 M KCl溶液中的反应速率约为在0.1 M NaClO4溶液中相应速率的6-8倍。根据速率和产物研究表明,在KCl溶液中反应速率的增加是由于氯离子对环氧乙烷部分的甲基碳的双分子攻击所致。1a对酸催化水解的反应性大于1b,但在无催化和氢氧化物离子催化水解中,1a的反应性小于1b。化合物1c在酸水中解反应中比1a快约73倍,在无催化反应中则快约11倍。根据反应活性考虑,提出H2O和HO-作为亲核剂添加到1a和1b的环氧部分的甲基碳上,而H2O添加到1c的乙酰碳上。