Do general nucleophilicity scales exist?

Abstract Comprehensive nucleophilicity scales including π ‐, n ‐ and σ ‐nucleophiles have been constructed using benzhydrylium ions and structurally related quinone methides as reference electrophiles. It is shown how the correlation (Eqn (1)) log k 20°C = s ( E + N ), where s and N are nucleophile‐specific parameters and E is an electrophile‐specific parameter, has recently been employed to characterize further classes of nucleophiles (phosphines, amines, isonitriles, trifluoromethanesulfonyl‐substituted carbanions) and electrophiles (2‐benzylideneindan‐1,3‐diones and benzylidenebarbituric acids). Practical applications of the reactivity parameters E , N and s for developing Friedel–Crafts alkylations in neutral alcoholic or aqueous solution and for characterizing nucleophilic organocatalysts will be discussed. Eventually, a new correlation equation will be presented, which includes Eqn (1), the Ritchie equation (nucleophilic additions to stabilized carbocations), and the Swain–Scott equation (nucleophilic substitutions of methyl halides) as special cases. Copyright © 2008 John Wiley & Sons, Ltd.