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The Duff reaction or hexamine aromatic formylation is a
The natural product 
Unlike other formylation reactions the Duff reaction is able to attach multiple aldehyde groups. If both ''ortho'' positions are vacant then a diformylation is possible, as in the formation of diformylcresol from ''p''-cresol. Conversion of phenol to the corresponding 1,3,5-trialdehyde has also been reported
formylation reaction
Formylation refers to any chemical processes in which a compound is functionalized with a formyl group (-CH=O). In organic chemistry, the term is most commonly used with regards to aromatic compounds (for example the conversion of benzene to benz ...
used in organic chemistry
Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic matter, organic materials, i.e., matter in its various forms that contain ...
for the synthesis of benzaldehyde
Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is among the simplest aromatic aldehydes and one of the most industrially useful.
It is a colorless liquid with a characteristic almond-li ...
s with hexamine
Hexamethylenetetramine (HMTA), also known as 1,3,5,7-tetraazaadamantane, is a heterocyclic organic compound with diverse applications. It has the chemical formula (CH2)6N4 and is a white crystalline compound that is highly soluble in water and p ...
as the formyl carbon source. The method is generally inefficient. The reaction is named after James Cooper Duff.
The reaction requires strongly electron donating substituents on the aromatic ring such as in a phenol
Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire.
The molecule consists of a phenyl group () ...
. Formylation occurs '' ortho'' to the electron donating substituent preferentially, unless the ''ortho'' positions are blocked, in which case the formylation occurs at the ''para'' position.
Examples
The modifiedsalicylaldehyde
Salicylic aldehyde (2-hydroxybenzaldehyde) is an organic compound with the formula . Along with 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde, it is one of the three isomers of hydroxybenzaldehyde. This colorless oily liquid has a bitter almo ...
3,5-di-''tert''-butylsalicylaldehyde is prepared by the Duff reaction:
The natural product syringaldehyde
Syringaldehyde is an organic compound that occurs in trace amounts widely in nature. Some species of insects use syringaldehyde in their chemical communication systems. ''Scolytus multistriatus'' uses it as a signal to find a host tree during ovip ...
can also be prepared by the Duff reaction. In this example, formylation occurs at the position para to the phenol
Phenol (also known as carbolic acid, phenolic acid, or benzenol) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile and can catch fire.
The molecule consists of a phenyl group () ...
ic OH.
Unlike other formylation reactions the Duff reaction is able to attach multiple aldehyde groups. If both ''ortho'' positions are vacant then a diformylation is possible, as in the formation of diformylcresol from ''p''-cresol. Conversion of phenol to the corresponding 1,3,5-trialdehyde has also been reported
Reaction mechanism
Thereaction mechanism
In chemistry, a reaction mechanism is the step by step sequence of elementary reactions by which overall chemical reaction occurs.
A chemical mechanism is a theoretical conjecture that tries to describe in detail what takes place at each stage ...
is related to that for the Reimer–Tiemann reaction, which uses chloroform as the formylating agent. Protonated hexamine ring-opens to expose an iminium group. Addition to the aromatic ring results in an intermediate at the oxidation state of a benzylamine. An intramolecular redox reaction then ensues, raising the benzylic carbon to the oxidation state of an aldehyde. The oxygen atom is provided by water on acid hydrolysis in the final step.
Historical references
Duff was a chemist at the College of Technology, Birmingham, around 1920–1950. who * * * * *See also
*Bouveault aldehyde synthesis
The Bouveault aldehyde synthesis (also known as the Bouveault reaction) is a one-pot substitution reaction that replaces an alkyl or aryl halide
In organic chemistry, an aryl halide (also known as a haloarene) is an aromatic compound in which one ...
* Bodroux-Chichibabin aldehyde synthesis
* Reimer-Tiemann reaction
* Sommelet reaction
The Sommelet reaction is an organic reaction in which a benzyl halide is converted to an aldehyde by action of hexamine and water. It is named after the French chemist Marcel Sommelet, who first reported the reaction in 1913.
:
One example, thi ...
* Vilsmeier-Haack reaction
References
{{DEFAULTSORT:Duff Reaction Addition reactions Name reactions Formylation reactions