Why do we have to use anhydrous AlCl3 in Gatterman-Koch Reaction?

In reference to a Gattermann-Koch reaction, such as the one shown below:


[![enter image description here](https://i.stack.imgur.com/eySTV.jpg)](https://i.stack.imgur.com/eySTV.jpg)


* Why does $\ce{AlCl\_3}$ have to be anhydrous?
* Why can't we just use normal $\ce{AlCl\_3(H2O)\_6}$?
* What would the reaction look like if we use $\ce{AlCl\_3(H2O)\_6}$?




Anhydrous $\ce{AlCl3}$ is used because it reacts violently with water [details here](https://chem.libretexts.org/Bookshelves/Inorganic_Chemistry/Supplemental_Modules_and_Websites_(Inorganic_Chemistry)/Descriptive_Chemistry/Elements_Organized_by_Period/Period_3_Elements/Chlorides_of_Period_3_Elements) and you then no longer have an aluminium compound that will react.


$\ce{AlCl3}$-catalysed reactions occur because it is a Lewis acid [definition here](http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch11/lewis.php) and readily accepts electron pairs. Water readily donates an electron pair which stops any other molecule from combining with it. This stops the reaction.


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