DIOXOLENIUM ION TRAPPING IN THE HYDROLYSIS OF CYCLIC ORTHO ESTERS - RATE-DETERMINING STEP

The dioxolenium ion formed during the acid-catalyzed hydrolysis of 2-(p-methoxyphenyl)-2-methoxy-l, 3-dioxolane in NH3OH+/NH2OH aqueous buffer solutions at 25°C is trapped efficiently by hydroxylamine without producing a corresponding increase in reaction rate; this indicates that trapping occurs after the rate-determining step and that dioxolenium ion formation is rate limiting in this hydrolysis reaction. Quantitative treatment of the data gives N+(NH2OH) = 1.44 ± 0.04, much lower than the standard value of 5.05, but this discrepancy could be due to reversibility of the hydroxylamine trapping reaction. © 1979, American Chemical Society. All rights reserved.