Dehydration of alcohol with Lewis acid aluminum trichloride
In the reaction $\ce{{}^{$i$}Pr-OH + H2O -&gt;[\ce{AlCl3}] C3H6 + 2H2O}$ the $\ce{H2O}$ on the reactant side and one of the $\ce{H2O}$s on the product side cancel, so you get $\ce{{}^{$i$}Pr-OH -&gt;[\ce{AlCl3}] C3H6 + H2O}$.

I think the reaction would also work with other Lewis acids. But it will rather proceed through the $\mathrm{E}1$ mechanism in any case. And it is likely that you'll get $\mathrm{S}_\mathrm{N}1$ side reactions.