Answer:
Step-by-step explanation:
Following are the problems to mono-alkylate the aromatic ring .
1 ) The carbocations formed in the process undergo rearrangement when the number of carbon to be added in the alkylation process is more than two .
2 ) The formed monoalkylated product is more reactive than reactant so reaction does not stop after monoalkylation . Dialkylation and tri alkylation product too are simultaneously formed . This can be controlled by using benzene in excess as reactant . Monohalo benzene or nitrobenzene are too weak to undergo Friedel craft reaction because of presence of deactivating
group .