STOICHIOMETRIC SOLVATION EFFECTS - PRODUCT-RATE CORRELATION FOR SOLVOLYSES OF PHENYL CHLOROFORMATE IN ALCOHOL-WATER MIXTURES

Solvolyses of phenyl chloroformate in water, D2O, CH3OD, 50% D2O-CH3OD , and in aqueous binary mixtures of acetone, ethanol and methanol are investigated at 25.0 degrees C. Product selectivities are reported at 25 degrees C for a wide range of ethanol-water and methanol-water solv ent compositions. The Grunwald-Winstein plots of first-order rate cons tants for phenyl chloroformate with Y-Cl (based on 2-adamantyl chlorid e) show marked dispersions into three separate lines for the three aqu eous mixtures with a small m value (m<0.2) and a rate maximum for aque ous alcohol solvents. Third-order rate constants, k(ww), k(aw), k(wa) and k(aa) were calculated from the observed k(kk) and k(ua) values tog ether with k(aw) and k(wa) calculated from the intercept and slope of the plot of 1/S vs. [alcohol]/[water]. The calculated rate constants, k(role) and mol % of ester agree satisfactorily with those of the obse rved rate constants, k(abs) and mol % of ester, supporting the stoichi ometric solvation effect analysis. The kinetic solvent isotope effects determined in water and methanol are consistent with the proposed mec hanism of the general base catalyzed and/or carbonyl addition for phen yl chloroformate solvolyses based on mass lau and stoichiometric solva tion effect studies.