Aluminium chloride (AlCl₃) is a compound of aluminium and chlorine. The solid has a low melting and boiling point, and is covalently bonded. It sublimes at 178 °C. Molten AlCl₃ conducts electricity poorly,[1] unlike more ionic halides such as sodium chloride. It exists in the solid state as a six-coordinate layer lattice. AlCl₃ adopts the "YCl₃" structure, featuring Al₃+ cubic close packed layered structure.[2] In contrast, AlBr₃ has a more molecular structure, with the Al₃+ centers occupying adjacent tetrahedral holes of the close-packed framework of Br− ions. Upon melting AlCl3 gives the dimer Al₂Cl₆, which can vaporise. At higher temperatures this Al₂Cl₆ dimer dissociates into trigonal planar AlCl₃, which is structurally analogous to BF₃.

The Friedel-Crafts reaction is the major use for aluminium chloride, for example in the preparation of anthraquinone (for the dyestuffs industry) from benzene and phosgene .

AlCl₃ is also widely used for polymerization and isomerization reactions of hydrocarbons . Important examples [1] include the manufacture of ethylbenzene , which used to make styrene and thus polystyrene , and also production of dodecylbenzene , which is used for making detergents .