Acetophenone is theorganic compound with theformula C6H5C(O)CH3. It is the simplest aromaticketone. This colorless, viscous liquid is a precursor to usefulresins and fragrances.[2]
Acetophenone is formed as a byproduct of thecumene process, the industrial route for the synthesis ofphenol andacetone. In the Hock rearrangement ofisopropylbenzene hydroperoxide, migration of a methyl group rather than the phenyl group gives acetophenone and methanol as a result of an alternaterearrangement of the intermediate:
C6H5C(CH3)2O2H → C6H5C(O)CH3 + CH3OH
The cumene process is conducted on such a large scale that even the small amount of acetophenone by-product can be recovered in commercially useful quantities.[2]
Acetophenone is also generated fromethylbenzene hydroperoxide. Ethylbenzene hydroperoxide is primarily converted to1-phenylethanol (α-methylbenzyl alcohol) in the process with a small amount of by-product acetophenone. Acetophenone is recovered or hydrogenated to 1-phenylethanol which is then dehydrated to produce styrene.[2]
Commercially significantresins are produced from treatment of acetophenone withformaldehyde and abase. The resultingcopolymers are conventionally described with the formula[(C6H5COCH)x(CH2)x]n, resulting fromaldol condensation. These substances are components ofcoatings andinks. Modified acetophenone-formaldehyde resins are produced by the hydrogenation of the aforementioned ketone-containing resins. The resultingpolyol can be further crosslinked withdiisocyanates.[2] The modified resins are found in coatings, inks andadhesives.
In instructional laboratories,[5] acetophenone is converted tostyrene in a two-step process that illustrates the reduction of carbonyls usingsodium borohydride and thedehydration of alcohols:
In the late 19th and early 20th centuries, acetophenone was used in medicine.[9] It was marketed as ahypnotic andanticonvulsant under brand name Hypnone. The typical dosage was 0.12 to 0.3 milliliters.[10] It was considered to have superior sedative effects to bothparaldehyde andchloral hydrate.[11] In humans, acetophenone is metabolized tobenzoic acid,carbonic acid, andacetone.[12]Hippuric acid occurs as an indirect metabolite and its quantity in urine may be used to confirm acetophenone exposure,[13] although other substances, liketoluene, also induce hippuric acid in urine.[14]
TheLD50 is 815 mg/kg (oral, rats).[2] Acetophenone is currently listed as a Group Dcarcinogen indicating that there is no evidence at present that it causes cancer in humans.
^Gadamasetti, Kumar; Tamim Braish (2007).Process Chemistry in the Pharmaceutical Industry, Volume 2. Taylor & Francis. pp. 142–145.ISBN978-0-8493-9051-7.