What Friedel and Crafts discovered
in 1877 was that halogenoalkanes can react with benzene in the presence
of AlCl3 to give alkylbenzenes. Alcohols and alkenes
can also be used.
Perhaps the single most important Friedel
Crafts reaction is the production of ethylbenzene from benzene,
the first stage in the manufacture of poly(phenylethene) or poly(styrene).Over
8 million tonnes is manufactured annually.
Benzene vapour and ethene pass over
heated aluminium chloride.
There is a serious problem, common
to Friedel-Crafts alkylations. Ethylbenzene is more reactive than
benzene. So it is difficult to stop more ethyl groups attaching
to the ring leading to a complicated mixture of substances.
The mixture of products which can result from Friedel Crafts alkylation
On a very different scale another useful product of Friedel -Crafts