Carbon kinetic isotope effects on the hydrolysis of aryl carbonates

Article abstract of DOI:10.1021/ja00172a013

Carbon kinetic isotope effects on the hydrolysis of aryl carbonates in 1:1 (v/v) dioxane-water at 25 °C at various pHs were used to calculate isotope effects on the reactions with hydroxide ion and with water. For diphenyl carbonate k_OH¹²/k_OH¹³ = 1.0482 and k_w¹²/k_w¹³ = 1.0509. For bis(p-methoxyphenyl)carbonate k_OH¹²/k_OH¹³= 1.0493 and k_w¹²/k_w¹³ = 1.0518. For bis(p-nitrophenyl)carbonate k_OH¹²/K_OH¹³ = 1.0476. The small change in the isotope effect with substituent group for both alkaline and neutral hydrolysis is in contrast to the large substituent effect on the rate constants for both reactions. The nearly constant isotope effect indicates that transition-state structures arc similar for all substrates.