:Sommelet reaction
{{Short description|Chemical reaction}}
{{Use dmy dates|date=December 2023}}
The Sommelet reaction is an organic reaction in which a benzyl halide is converted to an aldehyde by action of hexamine and water.{{JerryMarch}}{{cite journal |last1=Angyal |first1=S. J. |title=The Sommelet Reaction |journal=Organic Reactions |date=15 March 2011 |pages=197–217 |doi=10.1002/0471264180.or008.04|isbn=978-0-471-26418-7 }} It is named after the French chemist Marcel Sommelet, who first reported the reaction in 1913.{{cite journal | journal = Compt. Rend. | title = Sur un mode de décomposition des halogénoalcoylates d'hexaméthylène – tétramine | author = Marcel Sommelet | volume = 157 | pages = 852–854
| year = 1913 | url = http://gallica.bnf.fr/ark:/12148/bpt6k31103/f852.table}}
One example, thiophene-2-carboxaldehyde is prepared by the reaction of hexamine with 2-chloromethylthiophene.{{cite journal|title=2-Thiophenealdehyde|author=Kenneth B. Wiberg|journal=Org. Synth.|volume= 3|page=811|doi=10.15227/orgsyn.000.0005}} The reaction is formally an oxidation of the carbon.
Reaction mechanism and scope
The benzyl halide 1 reacts with hexamine to a quaternary ammonium salt 3, each time just alkylating one nitrogen atom. Then the benzylammonium undergoes an acid-catalyzed hydrolysis process.
Depending on the hydrolysis conditions, the hexamine unit might instead break apart, leaving a benzyl amine (the Delépine reaction).
The reaction can also be applied to the oxidation of benzylic amines. In this way, m-xylylenediamine can be converted to isophthalaldehyde.{{cite journal|first1=J. H. |last1=Ackerman|first2=A. R. |last2=Surrey|doi=10.15227/orgsyn.047.0076|title=Isophthalaldehyde|journal=Organic Syntheses|year=1967|volume=47|pages=76}}