Abstract The mechanism of the B ECKMANN rearrangement and the fragmentation of ketoximes 1 has been studied by determining rate constants and products in «80%» ethanol of several anti-alkyl-,-cycloalkyl-,-aralkyl-and-phenyl-ketoxime tosylates with stationary syn- methyl and-phenyl substituents. The ratio of fragmentation to amide formation is not related to reaction rate, but increases with the stability of the carbonium ion R+ formed, as ...