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Why do we have to use anhydrous AlCl3 in Gatterman-Koch Reaction?
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Adam Moss
Why do we have to use anhydrous AlCl3 in Gatterman-Koch Reaction?
Anhydrous $\ce{AlCl3}$ is used because it reacts violently with water details here 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 and readily accepts electron pairs. Water readily donates an electron pair which stops any other molecule from combining with it. This stops the reaction.
Anhydrous $\ce{AlCl3}$ is used because it reacts violently with water details here 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 and readily accepts electron pairs. Water readily donates an electron pair which stops any other molecule from combining with it. This stops the reaction.
@TooTea True. Equally, neither solvent nor reagents may posses hydrogens easily abstracted by the Lewis catalyst. Thus careful with amines, alcohols, phenols etc. which may (if not protected) additional Lewis acid ...More
@Buttonwood Oh, I see I should have worded that better. What I meant to say is that for any Friedel-Crafts-like reaction (not just Gatterman-Koch),the Lewis acid needs to be anhydrous (no matter if its AlCl₃ or something else, but the question was about AlCl₃).More
@TooTea The purpose of $\ce{AlCl3}$ is to act as a Lewis acid catalyst. Depending on the electron density of the aromatic system (Lewis basicity), the group to introduce to this ring by subsitution, reaction parameters (solvent, temperature, etc) it may be way too powerful (pyrroles, thiophenes) for a selective reaction and is replaced by less strong ones (e.g., $\ce{FeCl3} > \ce{SnCl4} > \ce{BF3} > \ce{TiCl4} > \ce{ZnCl2}$) to mention a few examples.More
Anhydrous $\ce{AlCl3}$ is used because it reacts violently with water details here 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 and readily accepts electron pairs. Water readily donates an electron pair which stops any other molecule from combining with it. This stops the reaction.
Anhydrous $\ce{AlCl3}$ is used because it reacts violently with water details here 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 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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