SOLVOLYSIS IN HYDROGEN AND DEUTERIUM OXIDE: II. STRONGLY SOLVATED SUBSTRATES

Rates of solvolysis are presented for a number of polar substrates in light and heavy water from which the rate ratios k/sub /D/sub 2/O/k/sub /H/sub 2/ O may be obtained. Compounds studied in clude methyl, o-methyl-, p-methyl-, p- methoxy-, and pfluoro-benzenesulfonate, the alpha - and beta -methylation series of alkyl methanesulfonates, methyl and isopropyl nitrate, methyl phosphate and sulfate, methane- and benzenesulfonyl chloride, and t-butyldimethylsulfonium iodide. The oxyanion esters, despite wide variation in reactivities, show very small variation in the rate ratios which lie near 0.9. The values for the chlorides are 0.61, and for the sulfonium salt, 0.95. The failure of the rate ratios to reflect the mechanistic changes required by variation in the alkyl groups and oxyanions is attributed to the structure of initial state solvation and the easy saturation of ratioaffecting structural changes by small charge development in the transition state. (auth)