Extended Grunwald-Winstein Analysis - LFER Used to Gauge Solvent Effects in p-Nitrophenyl Chloroformate Solvolysis

摘要

Specific rates of solvolysis at 25 °C for p-nitrophenyl chloroformate (>1) are analyzed using the extended (two-term) Grunwald-Winstein equation. For 39 solvents, the sensitivities (l = 1.68±0.06 and m = 0.46±0.04) towards changes in solvent nucleophilicity (l) and solvent ionizing power (m) obtained, are similar to those previously observed for phenyl chloroformate (>2) and p-methoxyphenyl chloroformate (>3). The observations incorporating new kinetic data in several fluoroalcohol-containing mixtures, are rationalized in terms of the reaction being sensitive to substituent effects and the mechanism of reaction involving the addition (association) step of an addition-elimination (association-dissociation) pathway being rate-determining. The l/m ratios obtained for >1, >2, and >3, are also compared to the previously published l/m ratios for benzyl chloroformate (>4) and p-nitrobenzyl chloroformate (>5).