Sommelet reaction

What is Sommelet reaction?

In 1913, Sommelet first reported a reaction that converts α-halomethyl aromatics, such as benzyl halides, into their corresponding aldehydes using hexamethylenetetramine (HMTA) treatment followed by mild acidic hydrolysis. This reaction is commonly known as the Sommelet reaction and is applicable to most aromatic compounds with an α-halomethyl group. It typically produces aldehydes in yields of 60-70 %, even in the presence of a small excess amount of water.

Sommelet reaction can also convert primary or secondary benzyl amines into aldehydes, but secondary amines are generally less reactive than primary amines.

Sommelet reaction - general reaction scheme
Sommelet reaction

X = Cl, Br, I, etc. (see list of acronyms)

However, there have been some unsuccessful attempts at using the Sommelet reaction, such as the preparation of 4,6-dimethoxy-s-triazine-2-aldehyde from 2-chloromethyl-4,6-dimethoxy-s-triazine, mesitaldehyde from α2-chloroisodurene, formyl poly[(methylphenyl) silanediyl] (PMPSi) from chloromethylated PMPSi, and benzaldehyde from N-methyl benzylamine. It should also be noted that aromatics with two chloromethyl groups ortho to each other generally yield a nitrogen-containing compound rather than the expected dialdehyde under the Sommelet reaction conditions.


Sommelet, M., Compt. Rend., 1913, 157, 852