Friedel-Crafts synthesis

A Friedel-Crafts synthesis occurs according to the scheme  

The recommended solvent is usually carbon disulfide, less often light petro--leum or nitromethane. A mixture of nitromethane and carbon disulfide has been introduced more recently and has the practical advantages of providing a homogeneous medium to the end of the reaction and of moderating the action of the aluminum chloride.506 

An excess of the aromatic hydrocarbon is generally used when it is cheap. 

When the condensation can lead to position isomers the relative amounts produced may be influenced by the nature of the solvent (e.g., for naphthalene, -derivatives in nitrobenzene, -derivatives in carbon disulfide, mixtures in light petroleum507). Aluminum chloride is the usual condensing agent. 

Care is needed when opening ampoules of aluminum chloride as there is usually an overpressure of hydrogen chloride inside. The coarse commercial material can generally be used without being powdered, since the reaction is usually of sufficient violence to require moderation and the coarse pieces still react smoothly. A finely powdered aluminum chloride should be used when the double compound formed in the reaction is first to be isolated or when the sluggishness of certain reactions necessitates stirring. 

---

Friedel-Crafts synthesis TALEIC ANHYDRIDE, MALEIC ACID AND FUMARIC ACID] (Vol 15)... 

They avoided the obvious Friedel-Crafts synthesis of (33), presumably to avoid the separation of o and p isomers, and used instead either Grignard route to (34),... 

By similar argument, bromoketone (36) is a good intermediate. There is no problem of o,p-isotners here, so the Friedel-Crafts synthesis is preferred. 

Durene, pentamethyl benzene and hexamethyl benzene have usually been prepared from benzene or one of its methylated derivatives by the Friedel-Crafts synthesis.1 Durene has been made from bromine derivatives of methylated benzenes by the Fittig reaction.2 It has also been obtained in 20 per cent yield by passing methyl alcohol and acetone vapors over heated alu-... 

B. The Phthaleins.—If two molecules of a phenol and one molecule of phthalic anhydride are caused to interact under the conditions which prevail during the Friedel-Crafts synthesis (Chap. IX. p. 342), the tendency of the ketone first formed to combine with a second molecule of the phenol outweighs condensation to the anthraquinone derivative in this way are formed the phthaleins, discovered by Baeyer in 1871. This process may be discussed by taking phenolphthalein as an example. 

Aluminium Chloride.—For the success of a Friedel-Crafts synthesis it is essential that the quality of the aluminium chloride used as catalyst should be beyond reproach. Commercial preparations are often partially decomposed and unfit for use in consequence of the entrance of moisture into insufficiently closed containers. In order to make sure, a small sample should be heated over a flame in a test tube held obliquely the whole, or at least the bulk, of the chloride should sublime. Preparations which are not too seriously decomposed can be made fit for use by resublimation. 

On account of the great reactivity of the substances taking part in the reaction, the choice of a solvent in the Friedel-Crafts synthesis is limited. The most important are carbon bisulphide, well purified petrol ether, chlorobenzene, and nitrobenzene. 

Often in the Friedel-Crafts synthesis the acid chloride can be replaced by the anhydride. The preparation of acetophenone (p. 346) is an example of this modification. 

A complete bibliography of the literature on the Friedel-Crafts synthesis is to be found in G. Krftnzlein, Aluminiumchlorid in der organischen Ghemie (Verlag Chemie, 1932). 

In addition to undergoing Friedel-Crafts arylations, cyanuric chloride has been used in the Friedel-Crafts synthesis of (67) from pyridine (equation 31) (68ZOB1368). 

Reaction XX. (6) Action of certain Anhydrous Metallic Halides (Aluminium Chloride, Aluminium Bromide, Aluminium and Hydrogen Chloride, Ferric Chloride) on a mixture of an Aromatic Hydrocarbon or certain Derivatives, and an Acyl Halide. (Friedel-Crafts.) (A. Ch., [6], 1, 518.)—This is an even more important application of the Friedel-Crafts synthesis than the methods of synthesising hydrocarbons (pp. 58, 60). The reactions involved are more readily controlled since the products, in presence of aluminium chloride, do not undergo further condensations. Usually these products have also the advantage of being more easily separated, for, as shown below in (iii.), the formation of isomers can be avoided. 

Friedel-Crafts Synthesis of Substituted Benzylidynetricobalt Nonacarbonyl Complexes from Chloromethylidynetricobalt Nonacarbonyl 1... 

At the time the chemistry of (OC)9Co3CCO+PF6 was being developed (27, SO), another route to this novel acylium ion was found in these laboratories (31, 32). This discovery was a result of our intention to adapt the Friedel-Crafts synthesis of benzylidynetricobalt nonacarbonyl complexes of Dolby and Robinson (15) to the preparation of alkyl derivatives of methylidynetricobalt nonacarbonyl, whose general preparation was not well in hand. The reaction chosen for investigation was the aluminum chloride-induced interaction of tetraalkyltin compounds with ClCCo3(CO)9 In analogy to a known ketone synthesis (33),... 

The first step in the Friedel-Crafts synthesis is formation of an electrophile capable of electrophilic substitution in the aromatic ring. Such an electrophile (or cation) is generated from an alkyl halide by its reaction with a Lewis acid, in this case boron trifluoride. Boron trifluoride... 

The Friedel-Crafts synthesis involves the union of a relatively active compound, like a halide, with a relatively stable hydrocarbon in the presence of an anhydrous halide of aluminum, iron or zinc. For example, when a mixture of benzyl chloride and benzene are treated in the cold with aluminum chloride, a vigorous reaction takes place with elimination of hydrogen chloride resulting in the union of the phenyl and benzyl radicals to form diphenylmethane ... 

---