Acetanilide

Preparation and properties

Acetanilide can be produced by reacting acetic anhydride with aniline: :

The preparation used to be a traditional experiment in introductory organic chemistry lab classes, but it has now been widely replaced by the preparation of either paracetamol or aspirin, both of which teach the same practical techniques (especially recrystallization of the product) but which avoid the use of aniline, a suspected carcinogen.

Acetanilide is slightly soluble in water, and stable under most conditions. Pure crystals are plate shaped and appear colorless, white, or in between.

Applications

Acetanilide is used as an inhibitor of hydrogen peroxide decomposition and is used to stabilize cellulose ester varnishes. Acetanilide is used for the production of 4-acetamidobenzenesulfonyl chloride, a key intermediate for the manufacture of the sulfa drugs.

In the 19th century acetanilide was one of a large number of compounds used as experimental photographic developers.

During the same period of time, acetanilide was introduced into medical practice as a fever-reducing agent under the name Antifebrin. It was one of the first aniline derivatives found to possess analgesic and antipyretic properties. However, its use was later discontinued due to toxic side effects, including methemoglobinemia, which led to cyanosis.

Acetanilide-derived herbicides have been used since the 1960s or earlier. These include alachlor, metolachlor and xylachlor.

Pharmaceutical use

Acetanilide was the first aniline derivative found to possess analgesic as well as antipyretic properties, and was quickly introduced into medical practice under the names of Antifebrin by A. Cahn and P. Hepp in 1886. prompted the search for supposedly less toxic aniline derivatives such as phenacetin. After several conflicting results over the ensuing fifty years, it was established in 1948 that acetanilide was mostly metabolized to paracetamol (acetaminophen) in the human body, and that it was this metabolite that was responsible for the analgesic and antipyretic properties. The observed methemoglobinemia after acetanilide administration was ascribed to the small proportion of acetanilide that is hydrolyzed to aniline in the body.

References

References

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