ABSTRACT
The substituent groups are divided in two different categories: electron withdrawing group (EWG) or electron donating group (EDG), and EWG/EDG by resonance or inductive effect. The electron donating groups by inductive effect are alkyl groups and sylanyl groups. There is one feature associated with EWGs and EDGs, which is specifically related to the regiochemistry/regioselectivity of the electrophilic aromatic substitution involving a monosubstituted aromatic compound. The aromatic nitration is the cusing nitronium ion as an electrophile. Two mechanisms are proposed for the aromatic nitration in gas phase: the polar mechanism and the SET mechanism. The aromatic sulfonation has many industrial applications and the most important sulfonating agents are sulfur trioxide and fuming sulfuric acid. The alkylation or aromatic compounds have been widely applied before Friedel-Crafts. The halogens, such as chlorine and bromine, can also be activated by Friedel-Crafts catalysts, such as aluminum chloride and iron bromide for aromatic halogenation.
