Propionyl chloride, reaction with benzen

Propiophenone. Propiophenone [93-55-0] (ethyl phenyl ketone) is a colorless Hquid with a flowery odor. It can be prepared by the Friedel-Crafts reaction of benzene and propionyl chloride in the presence of aluminum chloride (346), or by the catalytic reaction of benzoic acid and propionic acid in the presence of water (347). Propiophenone is commercially available (348), and is sold in Japan at 2700 Y/kg (349). It is used in the production of ephedrine, as a fragrance enhancer, and as a polymerization sensitizer. 

Phenylethyl Ketone. 200 g of finely powdered anhydrous aluminum chloride is suspended in 300 g of dry benzene in a flask that is cooled and equipped with a good stirring device. A mixture of 126 g of propionyl chloride and 105 g of benzene is added dropwise, with stirring, over 3 hours. After the 3 hours, the reaction mixture temp is kept at 50°. The contents of the flask are cooled and poured over crushed ice. Add 50 cc of coned HCl acid and remove the phenylethyl ketone and benzene by distillation with steam at 200-220° to yield 152 g of the ketone. 

We can kill two birds with one stone here both problems common to the Friedel-Crafts alkylation are solved when the acylation is used instead. Firstly, the product of the acylation is a ketone the reaction introduces a deactivating, electron-withdrawing, conjugating carbonyl group to the ring, so the product is less reactive than the starting material. Reaction will stop cleanly after one acylation. Here s benzene reacting with propionyl chloride. 

Obtained by reaction of propionyl chloride with catechol diethyl ether in the presence of aluminium chloride in refluxing benzene for 40 min (49%) [6850]. Also refer to [6851-6854]. 

Also obtained (by-product) by reaction of propionyl chloride with p-dimethoxy-benzene in methylene chloride in the presence of aluminium chloride at r.t. [7146,7147],... 

One preparative procedure for achieving this reaction involves the acylation of the magnesium enolate of diethyl malonate with an acid chloride in benzene solution (cf. Expt 5.96), and the resulting aclymalonic ester is then heated to 200 °C with an arylsulphonic acid to effect the decarbethoxylation step. An illustrative example is the preparation of ethyl 3-oxopentanoate (ethyl propionyl-acetate, Expt 5.177). 

Obtained by reaction of sodium azide with 4-[(4-propionyl-2-propyl-3-hydroxyphenyl)methoxy] benzene-acetonitrile in the presence of anunonium chloride in DMF at 105° for 20 h (32%) [7564]. 

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