Transition-State Structures for the Hydrolysis of Cyclic and Acyclic Carbonates

Article abstract of DOI:10.1021/jo00191a022

The hydrolysis of o-(4-nitrophenylene) carbonate (1) is third order in water while the hydrolysis of bis(4-nitrophenyl) carbonate (2) is second order in water.Proton inventories for both are downwardly curved indicating contributions by more than one proton to the observed kinetic solvent deuterium isotope effects of k_H2O/k_D2O = 2.46 and 2.20 for 1 and 2, respectively.The transition-state structure appears to involve a cyclic array of three water molecules in the case of 1, the cyclic carbonate.The transition-state structure for hydrolysis of the acyclic carbonate 2 involves only two water molecules with one acting as a general base to remove a proton from the nucleophilic water molecule.This has been referred to as a catalytic proton bridge transition state.Deslongchamp's theory of stereoelectronic control has been applied to an analysis of the proton inventories for the water-catalyzed hydrolysis of a cyclic and an acyclic carbonate ester.