Acetophenone is the organic compound with the formula C6H5C(O)CH3. It is the simplest aromatic ketone. This colorless, viscous liquid is a precursor to useful resins and fragrances.[2]
Production
Acetophenone is formed as a byproduct of the cumene process, the industrial route for the synthesis of phenol and acetone. In the Hock rearrangement of isopropylbenzene hydroperoxide, migration of a methyl group rather than the phenyl group gives acetophenone and methanol as a result of an alternate rearrangement 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 from ethylbenzene hydroperoxide. Ethylbenzene hydroperoxide is primarily converted to 1-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]
Uses
Precursor to resins
Commercially significant resins are produced from treatment of acetophenone with formaldehyde and a base. The resulting copolymers are conventionally described with the formula [(C6H5COCH)x(CH2)x]n, resulting from aldol condensation. These substances are components of coatings and inks. Modified acetophenone-formaldehyde resins are produced by the hydrogenation of the aforementioned ketone-containing resins. The resulting polyol can be further crosslinked with diisocyanates.[2] The modified resins are found in coatings, inks and adhesives.
In instructional laboratories,[6] acetophenone is converted to styrene in a two-step process that illustrates the reduction of carbonyls using sodium borohydride and the dehydration of alcohols:
In the late 19th and early 20th centuries, acetophenone was used in medicine.[11] It was marketed as a hypnotic and anticonvulsant under brand name Hypnone. The typical dosage was 0.12 to 0.3 milliliters.[12] It was considered to have superior sedative effects to both paraldehyde and chloral hydrate.[13] In humans, acetophenone is metabolized to benzoic acid, carbonic acid, and acetone.[14]Hippuric acid occurs as an indirect metabolite and its quantity in urine may be used to confirm acetophenone exposure,[15] although other substances, like toluene, also induce hippuric acid in urine.[16]
Toxicity
The LD50 is 815mg/kg (oral, rats).[2] Acetophenone is currently listed as a Group D carcinogen 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.
↑Engels, W.J.M.; Dekker, R.; De Jong, C.; Neeter, R.; Visser, S. (1997). "A comparative study of volatile compounds in the water-soluble fraction of various types of ripened cheese". International Dairy Journal. 7 (4): 255–263. Bibcode:1997IntDJ...7..255E. doi:10.1016/S0958-6946(97)00003-4.
