Acetophenone
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.<ref name=Ullmann>Template:Ullmann</ref>
Production
[edit]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:
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.<ref name=Ullmann/>
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.<ref name=Ullmann/>
Uses
[edit]Precursor to resins
[edit]Commercially significant resins are produced from treatment of acetophenone with formaldehyde and a base. The resulting copolymers are conventionally described with the formula Template:Chem2, 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.<ref name=Ullmann/> The modified resins are found in coatings, inks and adhesives.
Niche uses
[edit]Acetophenone is an ingredient in fragrances that resemble almond, cherry, honeysuckle, jasmine, and strawberry. It is used in chewing gum.<ref>Template:Citation</ref> It is also listed as an approved excipient by the U.S. FDA.<ref>Template:Cite web</ref>
Laboratory reagent
[edit]In instructional laboratories,<ref>Template:Cite journal</ref> acetophenone is converted to styrene in a two-step process that illustrates the reduction of carbonyls using sodium borohydride and the dehydration of alcohols:
A similar two-step process is used industrially, but reduction step is performed by hydrogenation over a copper chromite catalyst:<ref name=Ullmann/>
Being prochiral, acetophenone is also a popular test substrate for asymmetric hydrogenation experiments.
Drugs
[edit]Acetophenone is used for the synthesis of many pharmaceuticals.<ref> Template:Cite book</ref><ref> Template:Cite book</ref>
Natural occurrence
[edit]Acetophenone occurs naturally in many foods including apple, cheese, apricot, banana, beef, and cauliflower. It is also a component of castoreum, the exudate from the castor sacs of the mature beaver.<ref>Template:Cite journal</ref>
Pharmacology
[edit]In the late 19th and early 20th centuries, acetophenone was used in medicine.<ref>Template:Merck12th</ref> It was marketed as a hypnotic and anticonvulsant under brand name Hypnone. The typical dosage was 0.12 to 0.3 milliliters.<ref>Template:Cite book</ref> It was considered to have superior sedative effects to both paraldehyde and chloral hydrate.<ref>Template:Cite journal</ref> In humans, acetophenone is metabolized to benzoic acid, carbonic acid, and acetone.<ref>Template:Cite journal</ref> Hippuric acid occurs as an indirect metabolite and its quantity in urine may be used to confirm acetophenone exposure,<ref name=pubchem>Template:PubChem</ref> although other substances, like toluene, also induce hippuric acid in urine.<ref>Template:Cite web</ref>
Toxicity
[edit]The Template:LD50 is 815 mg/kg (oral, rats).<ref name=Ullmann/> Acetophenone is currently listed as a Group D carcinogen indicating that there is no evidence at present that it causes cancer in humans.