Give the structure of gaseous $AlCl_3$.

(N/A) In the gaseous state,$AlCl_3$ exists as a dimer,$Al_2Cl_6$.
Structure: The two $Al$ atoms are bridged by two $Cl$ atoms. Each $Al$ atom is $sp^3$ hybridized and forms four bonds (two terminal $Al-Cl$ bonds and two bridging $Al-Cl$ bonds).
Use: Being a Lewis acid,it acts as a catalyst in Friedel-Crafts alkylation and acylation,and also in electrophilic aromatic substitution reactions.