Solvent nucleophilicities of hexafluoroisopropanol/water mixtures

First‐order rate constants k 1 for the trapping of various donor‐ and acceptor‐substituted benzhydrylium ions in mixtures of 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP) and water ranging from 50 to 99% HFIP ( w / w ) were determined by laser flash photolytic generation of benzhydrylium ions from benzhydryl triarylphosphonium salts in these solvents. From these rate constants, we derived the solvent‐specific reactivity parameters N 1 and s N for HFIP/water mixtures as defined by the linear free energy relationship lg k 1 (20 °C) = s N ( N 1 + E ). Copyright © 2012 John Wiley & Sons, Ltd.