The kinetics of the reactions of carbanions, carboxylate anions, and primary and secondary amines with acylating agents were studied in acetonitrile and dimethyl sulfoxide (DMSO) under first-order conditions by UV/Vis spectrophotometry and conductimetry. Whereas reactions of a large variety of nucleophiles with ordinary carbanions and Michael acceptors generally follow the linear free energy relationship lg k₂ (20 °C) = s_N(N + E), separate correlation lines for different types of nucleophiles were found when (lg k₂)/s_N was plotted against N for the reactions with acyl derivatives 2–5. Even when nucleophilic attack is rate determining, the reactivities of acylating agents towards nucleophiles cannot be described by a single set of nucleophile-independent electrophilicity parameters.