Free accessResearch articleFirst published online 2007-8
Effects of Mixed Aqueous – Organic Cosolvents on the Rates of Cleavage of N-(2'-Hydroxyphenyl)Phthalimide (1) and N-(2'-Methoxyphenyl)-Phthalimide (2) in Alkaline Media
The effects of mixed H2O-OCS (where organic cosolvents (OCS) = methanol, ethanol, 1-propanol, 2-propanol, 1,4-dioxan and acetonitrile) on the first-order rate constants, kobs, for hydrolysis of 1 at 1.0 × 10−3 M NaOH and 2 at 2.0 × 10−3 M NaOH show a nonlinear decrease in kobs with increasing contents of OCS. The kobs - decreasing sensitivity of mixed H2O-OCS solvents within 5-X% v/v OCS, where X ranges from 50 to 90, is ca 2- to 9-fold larger for hydrolysis of 2 than that of 1. This observed characteristic difference is attributed to the occurrence of different rate laws in these reactions, i.e. rate = kw [1-][H2O] and rate = kOH [2][HO-] in the hydrolyses of 1 and 2, respectively.
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