Using electrophilic aromatic substitution, many functional groups are introduced onto the benzene framework.  Sulfonation of benzene involves the use of oleum, a mixture of sulfuric acid with sulfur trioxide. Sulfonated benzene derivatives are useful detergents.  In nitration, benzene reacts with nitronium ions (NO), which is a strong electrophile produced by combining sulfuric and nitric acids.  Nitrobenzene is the precursor to aniline.  Chlorination is achieved with chlorine to give chlorobenzene in the presence of a Lewis acid catalyst such as aluminium tri-chloride.