Benzene, alkylation discovery

They subsequently performed a reaction of 1-chloropentane with aluminum chloride using benzene as the solvent. Once again, they observed evolution of hydrogen chloride, but this time they found that 1-pentylbenzene ( amylbenzene ) was a major product In describing their discovery to the Chemical Society of France in 1877, they reported, With a mixture of [alkyl] chloride and hydrocarbon [an arene], the formation is established, in good yield, of hydrocarbons from the residues of the hydrocarbon less H and from the chloride less Cl. It is thus that ethylbenzene, amylbenzene, benzophenone, etc., are obtained. A general representation of the transformation is shown in the following equation. 

As demand for phenol started to grow owing to the increased use of phenolie resins and the advent of polycarbonates, more eompanies looked for proeess improvements which gave economie benefits. Although avoidanee of waste was not a prime target it became a faetor in the overall production costs. With the discovery of the cumene route (Seheme 2.3) for the co-production of phenol and acetone (propanone), the benzene sulfonation route quickly became obsolete in developed countries. Today the most modem phenol plants produce very little waste, the initial alkylation step being carried out using zeolite eatalysts, and overall yields based on benzene are almost 90%. 

In 1877, Charles Friedel and James Mason Crafts [30a, b] corporately discovered that treatment of amyl chloride with aluminum strips in benzene led to the formation of amylben-zene. This type of transformation was found to be general for alkyl halides and aromatics under the catalysis of Lewis acid. Along with the discovery of the closely related acylation [30c, d], these two men are best remembered by Friedel-Crafts reaction that bears their names. With various modem modifications that appeared in the Uterature, including enan-tioselective variants [31], Friedel-Crafts alkylation and acylation have already become one of the most powerful C—C bond forming reactions in organic chemistry [32]. These methods are recognized to date as of fundamental importance not only in acadania but also in industry [33]. As shown in Scheme 10.18, some heteroaromatics, instead of the aryl component or alcohol, and alkenes instead of halides can be used as suitable substrates. Also, other common Lewis acids like BFj, TiCl, SnCl, ScfOTOj, etc., and Brpnsted acids snch as HF, H SO, and superacids (e.g., HF SbFj, HS03-SbFj) can also used as catalysts. 

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