A Wagner–Meerwein rearrangement is a class of carbocation

Carbocation

A carbocation is an ion with a positively-charged carbon atom. The charged carbon atom in a carbocation is a "sextet", i.e. it has only six electrons in its outer valence shell instead of the eight valence electrons that ensures maximum stability . Therefore carbocations are often reactive,...

 1,2-rearrangement

1,2-rearrangement

A 1,2-rearrangement or 1,2-migration or 1,2-shift or Whitmore 1,2-shift 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...

 reaction

Rearrangement reaction

A rearrangement reaction is a broad class of organic reactions where the carbon skeleton of a molecule is rearranged to give a structural isomer of the original molecule. Often a substituent moves from one atom to another atom in the same molecule...

s in which a hydrogen

Hydrogen

Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

, alkyl or aryl

Aryl

In the context of organic molecules, aryl refers to any functional group or substituent derived from an aromatic ring, be it phenyl, naphthyl, thienyl, indolyl, etc....

 group migrates from one carbon to a neighboring carbon.

Several reviews have been published.

The rearrangement was first discovered in bicyclic terpene

Terpene

Terpenes are a large and diverse class of organic compounds, produced by a variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium. They are often strong smelling and thus may have had a protective...

s for example the conversion of isoborneol to camphene

Camphene

Camphene is bicyclic monoterpene. It is nearly insoluble in water, but very soluble in common organic solvents. It volatilizes readily at room temperature and has a pungent smell. It is a minor constituent of many essential oils such as turpentine, cypress oil, camphor oil, citronella oil,...

 :



The story of the rearrangement reveals that many scientists were puzzled with this and related reactions and its close relationship to the discovery of carbocations as intermediates.

In a simple demonstration reaction of 1,4-dimethoxybenzene

1,4-Dimethoxybenzene

1,4-Dimethoxybenzene is the para form of dimethoxybenzene, a volatile aromatic ether with a sweet floral odor. It occurs naturally in willow and zucchini . It appears to attract bees as it has a powerful response in their antenna.-Uses:Dimethoxybenzene is useful as an intermediate in synthesis...

 with either 2-methyl-2-butanol

2-Methyl-2-butanol

2-Methyl-2-butanol, also known as tert-amyl alcohol or amylene hydrate, is one of the isomers of amyl alcohol. It is a clear, colorless liquid with a strong odor of peppermint or camphor. In humans it possesses sedative, hypnotic, and anticonvulsant effects similar to ethanol through ingestion or...

 or 3-methyl-2-butanol

3-Methyl-2-butanol

3-Methyl-2-butanol is an organic chemical compound. It is used as a solvent and an intermediate in the manufacture of other chemicals....

 in sulfuric acid

Sulfuric acid

Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...

 and acetic acid

Acetic acid

Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...

 yields the same disubstituted product, the latter via a hydride shift of the cationic intermediate:

Currently, there are works relating to the use of skeletal rearrangement in the synthesis of bridged azaheterocycles.