[Pico]

Why would a Friedal-Craft reaction be unsuitable for preparing benzene derivitaves with non-branched alkyl chains, such as butylbenzene or p-butylbenzene? How should these compounds be sythesised?

[kriggy]

Because once the first alkylation is finished, the monosubstitued benzene is more reactive towards another alkylation so you most likely end with mixture of mono, bi and trisubstitued benzene.

You can synthetize by using F-C acylation and then reduce the carbonyl function.

So its not entirely true that its not suitable.

[darkdevil]

Because rearrangement may occur for linear haloalkanes. For example when u react benzene with 1-bromopropane (a primary alkylhalide), one can seldom obtain n-propylbenzene, but a sec-propylbenzene. Since a 2^o carbocation is more stable than a 1^o one within the FC conditions.


More info here: http://chemwiki.ucdavis.edu/Organic_Chemistry/Organic_Chemistry_With_a_Biological_Emphasis/Chapter_15%3A_Electrophilic_reactions/Section_15.7%3A_Carbocation_rearrangements

[darkdevil]

The unbrached compounds can be synthesized with FC acylation, and then reduction if you must start with benzene.
Or, more simply using a halobenzene and make a grignard reagent and added the primary haloalkane.