Phenylacetone

Structural formula
General
Surname	Phenylacetone
other names	1-phenyl-2-propanone Benzyl methyl ketone P2P
Molecular formula	C 9 H 10 O
Brief description	colorless liquid
External identifiers / databases
CAS number 103-79-7 EC number 203-144-4 ECHA InfoCard 100,002,859 PubChem 7678 ChemSpider 21106366 Wikidata Q418831
properties
Molar mass	134.18 g mol −1
Physical state	liquid
density	1.01 g cm −3 (20 ° C)
Melting point	−15 ° C
boiling point	216 ° C
solubility	practically insoluble in water soluble in ethanol , diethyl ether , benzene and xylene
Refractive index	1.5165
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Phenylacetone is a colorless to slightly yellow liquid with a strong, characteristic odor that is used in the chemical and pharmaceutical industries.

presentation

Phenylacetone ( 4 ) can be prepared in a wide variety of ways. The most economical is the Dakin-West reaction of phenylacetic acid ( 1 ) and acetic anhydride ( 2 ) with base catalysis. The enolate of the mixed anhydride attacks another molecule 2 , splits off acetate and the resulting β-keto acid 3 decarboxylates to 4 .

Another method (II) uses the acetates of divalent metals, especially lead , as the source of acetyl .

The reaction of methyllithium with the lithium salt of phenylacetic acid represents a further elegant route to 4 , even if half of the MeLi has to be used for the deprotonation of 1 .

Further syntheses that manage without the monitored substance phenylacetic acid are possible, but due to the price or the toxicity of individual starting materials or due to low yields, they can only be carried out on a laboratory scale. I.a. it is possible to react benzene with chloroacetone in a Friedel-Crafts alkylation (a) or to combine acetone itself with benzene in a radical manner (b); the manganese (III) acetate required for this is the limiting reagent.

Ketones can be prepared by the reaction of organometallic reagents with nitriles : In our case, this means that either trimethylaluminum (or methylmagnesium halide) can be allowed to act on benzyl cyanide (a) or, on the other hand, benzyl magnesium bromide can act on acetonitrile (b); in both cases hydrolysis of the intermediate imine gives ketone 4 .

The oxidation of α-methylstyrene with thallium (III) salts in methanol (VI) is also of interest : After the addition to the double bond, Tl (I) is split off and a sigmatropic rearrangement occurs at the intermediate carbocation . The resulting dimethyl ketal is then acid catalysis hydrolyzed .

Another way is the condensation of benzaldehyde and nitroethane , which gives phenyl-2-nitropropene , which can be reduced to phenylacetone via an oxime as an intermediate.

use

Phenylacetone is used for the synthesis of pesticides and pharmaceuticals . Examples are diphacinone (a rat poison ) or amphetamine (by reductive amination ). Due to their potential use in the synthesis of various amphetamines, both manufacture and sale require a permit.

Legal

Due to its suitability as a starting material in methamphetamine synthesis , phenylacetone belongs to category I of the monitored chemicals in the EU and Switzerland according to the Basic Substance Monitoring Act . This means that manufacturing, trading and importing and exporting without a permit are punishable by law.

Individual evidence

1. ↑ ^{a b c} Entry on 1-phenylpropan-2-one. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.
2. ↑ ^{a b c d e} Entry on phenylacetone in the GESTIS substance database of the IFA , accessed on May 10, 2018(JavaScript required) .