the 1,2-shift can be high (up to 60 kcal/mol or 250 kJ/mol) but much less than that required for a proton abstraction to an aryne (82 kcal/mol or 340 kJ/mol). In alkene radicals proton abstraction to an alkyne is preferred. 1,2-Rearrangements The following mechanisms involve a 1,2-rearrangement: 1,2-Wittig rearrangement Alpha-ketol rearrangement Beckmann rearrangement Benzilic acid rearrangement Brook rearrangement Criegee rearrangement Curtius rearrangement Dowd–Beckwith ring expansion reaction Favorskii rearrangement Friedel–Crafts reaction Fritsch–Buttenberg–Wiechell rearrangement Halogen dance rearrangement Hofmann rearrangement Lossen rearrangement Pinacol rearrangement Seyferth–Gilbert homologation SN1 reaction (generally) Stevens rearrangement Stieglitz rearrangement Wagner–Meerwein rearrangement Westphalen–Lettré rearrangement Wolff rearrangement 1,3-rearrangements 1,3-rearrangements take place over 3 carbon atoms. Examples: the Fries rearrangement a 1,3-alkyl shift of verbenone to chrysanthenone References Rearrangement reactions