Rearrangement reaction

$${\displaystyle -\underset{\genfrac{}{}{0ex}{}{|}{{\displaystyle \text{R}}}}{\text{C}}-\text{C}-\text{C}-⟶-\text{C}-\underset{\genfrac{}{}{0ex}{}{|}{{\displaystyle \text{R}}}}{\text{C}}-\text{C}-}$$

A rearrangement is not well represented by simple and discrete electron transfers (represented by curved arrows in organic chemistry texts). The actual mechanism of alkyl groups moving, as in Wagner–Meerwein rearrangement, probably involves transfer of the moving alkyl group fluidly along a bond, not ionic bond-breaking and forming. In pericyclic reactions, explanation by orbital interactions give a better picture than simple discrete electron transfers. It is, nevertheless, possible to draw the curved arrows for a sequence of discrete electron transfers that give the same result as a rearrangement reaction, although these are not necessarily realistic. In allylic rearrangement, the reaction is indeed ionic.

1,2-rearrangements

A 1,2-rearrangement is an organic reaction where a substituent moves from one atom to another atom in a chemical compound. In a 1,2 shift the movement involves two adjacent atoms but moves over larger distances are possible. Skeletal isomerization is not normally encountered in the laboratory, but is the basis of large applications in oil refineries. In general, straight-chain alkanes are converted to branched isomers by heating in the presence of a catalyst. Examples include isomerisation of n-butane to isobutane and pentane to isopentane. Highly branched alkanes have favorable combustion characteristics for internal combustion engines.

Further examples are the Wagner–Meerwein rearrangement:

and the Beckmann rearrangement, which is relevant to the production of certain nylons: