Benzene is a nucleophile due to its π electrons, but its reactions are slow relative to those of alkenes with the same electrophile (Br2 for example). Thus reagents for the aromatic electrophilic substitutions shown below are a combination of the source of the substitituent group (electrophile) and a catalyst which activates the electrophile.
| forming a benzene-carbon bond | |||
 | CH3COCl AlCl3 |  | |
| CH3Cl AlCl3 |  | ||
| forming a benzene-nitrogen bond | |||
| HNO3 conc H2SO4 |  | |
| forming a benzene-halogen bond | ||
| Br2 FeBr3 |  |
| Cl2 FeCl3 |  | |