Correlation of the Rates of Solvolysis of 4-Morpholinecarbonyl Chloride Using the Extended Grunwald-Winstein Equation

The rates of solvolysis of 4-morpholinecarbonyl chloride (MPC) have measured at 35.0 degrees C in water, D2O, CH3OD, and in aqueous binary mixtures of acetone, ethanol, methanol, and 2,2,2-trifluoroethanol. An extended (two-term) Grunwald-Winstein equation correlation gave sensitivities towards changes in solvent nucleophilicity and solvent ionizing power as expected for a dissociative S(N)2 and/or S(N)1 (ionization) pathway. For nine solvents specific rates were determined at two additional temperatures and higher enthalpies and smaller negative entropies of activation were observed, consistent with the typical dissociative S(N)2 or S(N)1 (ionization) pathway. The solvent deuterium isotope effect values for the hydrolysis of MPC of k(H2O)/k(D2O) = 1.27 and for the methanolysis of MPC of k(MeOH)/k(MeOD) = 1.22 are typical magnitudes of the S(N)1 or ionization mechanism.