Tetrachloroaluminate
Tetrachloroaluminate − is an anion formed from aluminium and chlorine. The anion has a tetrahedral shape, similar to carbon tetrachloride where carbon is replaced with aluminium. Some tetrachloroaluminates are soluble in organic solvents, creating an ionic non-aqueous solution, making them suitable as component of electrolytes for batteries. E.g. lithium tetrachloroaluminate is used in some lithium batteries.Formation
Tetrachloroaluminate ions are formed as intermediaries in the Friedel–Crafts alkylation reaction, in which Aluminium chloride is used as a catalyst. The Friedel-Crafts alkylation reaction can be broken into three steps, as follows:
Step 1: The alkyl halide reacts with the strong Lewis acid to form an activated electrophile composed of the tetrachloroaluminate ion and the alkyl group.
Step 2: The aromatic ring reacts with the activated electrophile forming an alkyl-benzenonium carbocation.
Step 3: The alkyl-benzenonium carbocation reacts with a tetrachloroaluminate anion, regenerating the aromatic ring and the Lewis acid and forming hydrochloric acid.
