Friedel-Crafts reaction bromobenzene

What is an immediate precursor of toluene " Benzene, which could be methylated in a Friedel-Crafts reaction. Alternatively, "What is an immediate precursor of bromobenzene " Benzene, which could be brominated. 

Next ask yourself, What is an immediate precursor ofp-bromotolueneT Perhaps toluene is an immediate precursor because the methyl group would direct bromination to the ortho and para positions, and the isomeric products could be separated. Alternatively, bromobenzene might be an imme ate precursor because we could carry out a Friedel-Crafts methylation li obtain para product. Both answers are satisfactory, although, in view of 1 difficulties often observed with polyalkylation in Friedel-Crafts reactions, bromination of toluene may be the better route. ... 

The best results were obtained when the less activated substrate was used in the initial acylation and the more activated arene was used as the subsequent acceptor. With less activated substrates, such as diloro- and bromobenzenes, the chlorocarbonylation required a longer time and higher temperatures. Yields of 54-77% were obtained (Table 4.43) using 1.0 equiv. of each arene, rather than the several fold excess of one or the other often previously employed [950], Moreover, the conditions of the second Friedel-Crafts reaction are sufficiently mild that even an 0-... 

There are a great many aspects to the Friedel-Crafts method that Strike does not have the space to go into. Friedel-Crafts works better if chloro or bromobenzene and their X counterparts are used in place of plain old benzene. Also, there is a significant amount of unwanted byproducts and molecular rearrangements that accompany this sort of reaction. Strike strongly suggests that people read more about this method before they attempt any such reaction. 

Partial rate factors may be used to estimate product distributions in disubstituted benzene derivatives. The reactivity of a particular position in o-bromotoluene, for example, is given by the product of the partial rate factors for the corresponding position in toluene and bromobenzene. On the basis of the partial rate factor data given here for Friedel-Crafts acylation, predict the major product of the reaction of o-bromotoluene with acetyl chloride and aluminum chloride. 

For the synthesis of orfbo-bromotoluene we use a sulphonic acid. o-Bromotoluene could be synthesised by bromination of toluene or by Friedel-Crafts alkylation of bromobenzene (Fig. T). However, the reaction would also give the para substitution product and this is more likely if the electrophile is hindered from approaching the ortho position by unfavourable steric interactions. Alternatively we can substitute a group at the para position before carrying out the bromination. 

Preparation by reaction of o-methoxybenzoyl chloride with bromobenzene in the presence of aluminium chloride (Friedel-Crafts) [910]. 

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