STOICHIOMETRIC SOLVATION EFFECTS .4. PRODUCT-RATE CORRELATIONS FOR SOLVOLYSES OF P-METHOXYPHENYL CHLOROFORMATE IN ALCOHOL-WATER MIXTURES

Solvolyses of p-methoxyphenyl chloroformate in water, D2O, CH3OD, 50% D2O-CH3OD, and in aqueous binary mixtures of acetone, ethanol and meth anol are investigated at 25.0 degrees C. Product selectivities are rep orted at 25 degrees C for a wide range of ethanol-water and methanol-w ater solvent compositions. The Grunwald-Winstein plots of first-order rate constants for p-methoxyphenyl chloroformate with Y-C1 (based on 1 -adamantyl chloride) show marked dispersions into three separate curve s for the three aqueous mixtures with a small m value and a rate maxim um for aqueous alcohol solvents. Third-order rate constants, k(ww), k( aw), k(wa), and k(aa) were calculated from the observed k(ww) and k(aa ) values together with k(aw) and k(wa) calculated from the intercept a nd slope of the plot of 1/S vs. [alcohol]/[water]. The calculated rate constants, k(calc), and mol % of ester agree satisfactorily with thos e of the observed rate constants, k(obs) and mol % of ester, supportin g the stoichiometric solvation effect analysis. The kinetic solvent is otope effects determined in water and methanol are consistent with the proposed mechanism of the general base catalyzed carbonyl addition-el imination.