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Topic: Why use AlCl3?  (Read 3350 times)

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Offline zsinger

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Why use AlCl3?
« on: March 16, 2014, 01:15:09 PM »
All,
I am about to perform a Reduction by iron metal and hydrochloric acid.  I am wondering what the point of the Ferrous Chloride, which the paper calls for, is?  I see no need for it, as FeCl2 is generated in situ……I have examined several suggested mechanisms, drawn them all out by hand, and STILL cannot find where the 1g of FeCl3 comes into play….Any help appreciated.  I know it is prob. a Lewis Acid catalyst to kickstart things, however I just do not see what it coordinates with? 
                -Zack
« Last Edit: March 16, 2014, 01:28:03 PM by zsinger »
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Offline zsinger

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Re: Why use AlCl3?
« Reply #1 on: March 19, 2014, 08:34:37 PM »
Any help appreciated?  I cannot find it after checking literature.
         -Zack
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Offline zsinger

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Re: Why use AlCl3?
« Reply #2 on: March 22, 2014, 12:57:05 PM »
OK……This is what I have come to figure, so somebody please correct me if I am wrong.  I believe that this is a catalyst.
I have reviewed the most advanced literature I can on this reaction, and it is lacking on that last explanation.  Anyways, Im going to use it, as I have it at hand and the paper calls for it, so why mess with what is said to work like a charm :).

FeCl3 is a Lewis Acid Catalyst in FCA, and Ring reactions, however I see nothing that this LA accepts extra electrons from?  In Fact, the extra electrons are contained in the reactive metal itself and need NO LA to donate them, but can rather donate them directly to a Nitro Group for instance.
           -Zack
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Offline discodermolide

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Re: Why use AlCl3?
« Reply #3 on: March 22, 2014, 01:15:10 PM »
This may well be a redox system where the Fe complexes to the nitro group and electrons start jumping about, eventually reducing it to the amine.
It usually works well.
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Offline zsinger

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Re: Why use AlCl3?
« Reply #4 on: March 22, 2014, 03:21:25 PM »
That is precisely what it is.  Just can't see where the FeCl3 fits it :).  Im running the reduction tonight, so I will post conditions, and results.
       -Z
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Offline zsinger

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Re: Why use AlCl3?
« Reply #5 on: March 22, 2014, 03:24:23 PM »
GOT IT!  How about this:  I'll bet it is a catalyst by keeping the [HCl] higher than it normally would be by shifting the equation to the left (I.E. making HCl for reductive purposes).  :)
         -Z
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Offline orgopete

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Re: Why use AlCl3?
« Reply #6 on: March 23, 2014, 11:18:32 PM »
GOT IT!  How about this:  I'll bet it is a catalyst by keeping the [HCl] higher than it normally would be by shifting the equation to the left (I.E. making HCl for reductive purposes).  :)
         -Z

This is unlikely as HCl is consumed in the reaction to form FeCl3 and H2O.

This is a difficult post to answer as it is confusing. The title is, "Why use AlCl3", but nothing in the post refers to AlCl3. The post refers to ferrous chloride, a reductant, but also the addition of one gram of ferric chloride. Okay, I'm confused.

We don't know the scale or anything further about the reaction, but I can imagine ferrous chloride being added because it would be soluble while metallic iron is not. For the purposes of increasing the initial rate, I can see why this might be added. Indeed, the iron will react and dissolve, including forming ferrous chloride. An addition of ferrous chloride may speed up that process.
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Offline zsinger

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Re: Why use FeCl3?
« Reply #7 on: March 24, 2014, 01:28:45 AM »
I know, I could not change it.  I figured it out.
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