The Sommelet–Hauser rearrangement (named after M. Sommelet and

Charles R. Hauser Charles Roy Hauser (March 8, 1900 – January 6, 1970) was an American chemist. Hauser was a member of the National Academy of SciencesBradsher, Charles KCharles Roy Hauser.Biographical Memoirs, National Academy of Sciences. National Academies Pr ...

''Rearrangements of Benzyltrimethylammonium Ion and Related Quaternary Ammonium Ions by Sodium Amide Involving Migration into the Ring'' Simon W. Kantor, Charles R. Hauser J. Am. Chem. Soc., 1951, 73 (9), pp 4122–4131 ) is a

rearrangement reaction In organic chemistry, 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 at ...

of certain

benzyl In organic chemistry, benzyl is the substituent or molecular fragment possessing the structure . Benzyl features a benzene ring () attached to a methylene group (). Nomenclature In IUPAC nomenclature, the prefix benzyl refers to a substituent ...

quaternary ammonium salt In organic chemistry, quaternary ammonium cations, also known as quats, are positively-charged polyatomic ions of the structure , where R is an alkyl group, an aryl group or organyl group. Unlike the ammonium ion () and the primary, secondary, ...

s. The reagent is

sodium amide Sodium amide, commonly called sodamide (systematic name sodium azanide), is the inorganic compound with the formula . It is a salt composed of the sodium cation and the azanide anion. This solid, which is dangerously reactive toward water, is whit ...

or another alkali metal amide and the reaction product a ''N'',''N''-dialkylbenzylamine with a new

alkyl In organic chemistry, an alkyl group is an alkane missing one hydrogen. The term ''alkyl'' is intentionally unspecific to include many possible substitutions. An acyclic alkyl has the general formula of . A cycloalkyl group is derived from a cy ...

group in the

aromatic ortho position Arene substitution patterns are part of organic chemistry IUPAC nomenclature and pinpoint the position of substituents other than hydrogen in relation to each other on an aromatic hydrocarbon. ''Ortho'', ''meta'', and ''para'' substitution * I ...

. For example, benzyltrimethylammonium iodide, C₆H₅CH₂)N(CH₃)₃, rearranges in the presence of sodium amide to yield the ''o''-methyl derivative of ''N'',''N''-dimethylbenzylamine. : SommeletHauserReaction

Mechanism

The benzylic methylene proton is acidic and deprotonation takes place to produce the benzylic

ylide An ylide () or ylid () is a neutral dipolar molecule containing a formally negatively charged atom (usually a carbanion) directly attached to a heteroatom with a formal positive charge (usually nitrogen, phosphorus or sulfur), and in which both ...

(1). This ylide is in equilibrium with a second ylide that is formed by deprotonation of one of the ammonium methyl groups (2). Though the second ylide is present in much smaller amounts, it undergoes a 2,3-sigmatropic rearrangement because it is more reactive than the first one and subsequent aromatization to form the final product (3).Ahluwalia, V. K., and R. K. Parashar. Organic Reaction Mechanisms. Harrow, U.K.: Alpha Science International, 2005. Print. : The Stevens rearrangement is a competing reaction.

References

{{DEFAULTSORT:Sommelet-Hauser rearrangement Rearrangement reactions Name reactions