Industrial Friedel-Crafts alkylation

Friedel-Crafts alkylation using alkenes has important industrial appHcations. The ethylation of benzene with ethylene to ethylbenzene used in the manufacture of styrene, is one of the largest scale industrial processes. The reaction is done under the catalysis of AlCl in the presence of a proton source, ie, H2O, HCl, etc, although other catalysts have also gained significance. 

Despite the use of new catalys.s for manufacturing some industrial organic chemicals, many well-known classical reactions still abound. The Friedel-Crafts alkylation is one of the first reactions studied in electrophilic aromatic substitution. It is used on a large scale for making ethylbenzene. 

One of the most common examples of an electrophilic aromatic substitution is Friedel-Crafts alkylation [40], These days, many important industrial processes are based on this type of Friedel-Crafts-chemistry [41]. The manufacture of high-octane gasoline, ethylbenzene, synthetic rubber, plastics and detergent alkylates are examples. Moreover, the Friedel-Crafts alkylation is among the most fundamental and convenient processes for C—C bond formation on arenes, especially for the synthesis of fine chemicals and agrochemicals containing functionalized arenes and heteroarenes. 

Two of the reactions that are used in the industrial preparation of detergents are electrophilic aromatic substitution reactions. First, a large hydrocarbon group is attached to a benzene ring by a Friedel-Crafts alkylation reaction employing tetrapropene as the source of the carbocation electrophile. The resulting alkylbenzene is then sulfonated by reaction with sulfuric acid. Deprotonation of the sulfonic acid with sodium hydroxide produces the detergent. 

Another catalytic methodology that is widely used for C-C bond formation is the Heck and related coupling reactions [86, 87]. The Heck reaction [88] involves the palladium-catalysed arylation of olefinic double bonds (Fig. 1.31) and provides an alternative to Friedel-Crafts alkylations or acylations for attaching carbon fragments to aromatic rings. The reaction has broad scope and is currently being widely applied in the pharmaceutical and fine chemical industries. For example, Albemarle has developed a new process for the synthesis of the anti-in-... 

One very important alkylation reaction is the Friedel-Crafts alkylation reaction, used for the alkylation of aromatic species, which was discovered in 1877. Alkylation is used industrially to produce basic building blocks for the synthesis of more elaborate materials. One commonly used application is in the production of antiknock gasoline. In medicine, alkylation of deoxyribonucleic acid (DNA) is used in chemotherapy to damage the DNA of cancer cells. In this section, the three principle types... 

To convert these reactions into efficient industrial processes an important requisite is that they are catalytic. Friedel-Crafts alkylations meet this requirement and in some cases are still carried out today with conventional catalysts such as AICI3. Many acid- and base-catalyzed C-C bond-forming reactions are practised on a small scale. We shall not treat these reactions except to introduce... 

Friedel-Crafts alkylation processes were traditionally operated at 65-70°C with AICI3 and at 40-60°C with HF. A variety of solid acid catalysts have been developed at the laboratory level, mainly based on zeolites, heteropolyacids or sulfated zirconia (zirconia treated with sulfuric acid). The most recent industrial achievement is the Detal process (UOP-CEPSA) which is based on silica-alumina impregnated with HF. The selectivity towards linear alkylbenzenes exceeds 95%. The cymene processes use AICI3 in the liquid phase or supported phosphoric acid as catalysts. 

Despite their seemingly wide variety, Friedel-Crafts reactions can be divided into two general categories alkylations and acylations. Within these two broad areas, there is considerable diversity. Friedel-Crafts alkylations allow C—C bond formation in both aromatic and aliphatic systems, and are of substantial synthetic and industrial significance. 

The synthetic detergents industry originated in the 1940s, when it was found that a new anionic surfactant type—alkylbenzene sulfonate—had detergent characteristics superior to those of natural soaps. The first surfactant of this kind was sodium dodecylbenzene sulfonate (SDBS). This material was produced by the Friedel-Crafts alkylation reaction of benzene with propylene tetramer (a mixture of Co olefin isomers), followed by sulfonation with oleum or sulfur trioxide and then neutralization, usually with sodium hydroxide. The alkylation was typically performed using homogenous acid catalysts, such as HF or sulfuric acid. 

The Friedel-Crafts alkylation of aromatic compounds is of great importance in laboratory synthesis and industrial production. For example, the industrial processes for ethylbenzene, cumene and linear alkylbenzenes, etc., are on the base of this kind of reaction. It is well known that the drawbacks of the traditional acid catalysts such as A1Q3, H SO, and HF do great harm to the equipment and the environment, and these catalysts cannot be reused after the usual aqueous work-up besides, most of the reactions are carried out in the harmful and volatile organic solvents which can cause the environmental pollution aU of these problems need the replacement of the solvents or the acid catalysts. In this context, room-temperature ionic liquids have been iuCTeasingly employed as green solvents. 

Friedel-Crafts acylation is related to Friedel-Crafts alkylation, with an acylium cation acting as the electrophile. However, in industrial aromatic chemistry, because of the high consumption of catalyst, this reaction is of much less importance than Friedel-Crafts alkylation. Nonetheless, it has been used, for example, in the manufacture of anthraquinone from phthalic anhydride and benzene. 

Moreover, starting from n-decane or n-dodecane, this protocol resulted in the formation of non-branched n-alkylarenes which are not accessible via the classical industrial route involving Friedel-Crafts alkylation of arenes with linear olefins. For example, when the dehydroaromatization of n-decane was catalyzed by 14a,... 

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