When n-Hexane is heated with anhydrous ${\mathrm{AlCl}}_3$ and $\mathrm{HCl}$ gas at $573\mathrm{K}$ under a pressure of about $30-35\mathrm{atm}$ it Isomerises to give a branched chain alkanes.

${\mathrm{CH}}_3{\left({\mathrm{CH}}_2\right)}_4{\mathrm{CH}}_3\underset{\underset{△}{\mathrm{HCl}}}{\overset{\mathrm{Anhy}.{\mathrm{AlCl}}_3}{\to }}\underset{2-\mathrm{methylpentane}}{{\left({\mathrm{CH}}_3\right)}_2{\mathrm{CHCH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_3}+3-\mathrm{methylpentane}$

Major product in the above reaction is 2-methylpentane.