Halogen mobility in S N2 reactions of carbonyl compounds. Comparisons with aromatic halogen mobility

Kinetic studies, using conductimetric techniques, have been carried out for isopropanolysis (solvolysis) reactions of some alkanoyl, benzoyl, and perfluoroalkanoyl halides, viz. butanoyl and benzoyl fluorides, chlorides, and bromides and perfluoropentanoyl fluoride and chloride. The halogen mobility orders, F Cl < Br, have been compared with mobility patterns recognised for SN reactions at saturated and aromatic carbon, and have been discussed in mechanistic terms. The substrate class reactivity order is perfluoroalkanoyl benzoyl, alkanoyl. The actual ratios depend on which halogen is displaced, the ratios being larger in displacement of fluorine.