Solvolysis of (4-Nitrophenoxy)ethylene Oxides

Article abstract of DOI:10.1021/jo00084a012

(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 1a and 1b 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 attact of chloride ion at the methylene carbon of the epoxy 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(1-) 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.