AlCl3 + NH3 reaction?

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Does anyone know what the products would be if aluminum trichloride is mixed with ammonia gas?
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AlCl2NH2 + HCl(g). Or AlCl(NH2)2 + 2HCl(g). I have used this many times in organic synthesis in converting esters to primary amides in toluene (similar to using trimethylaluminum, which works better). There is not a ton of real lit. out there as to what species is actually present but it works. The only reason I had to use it was because when I used the trimethylaluminum variation, AlMeClNH2, I got a Friedel-Crafts alkylation on a halide which was surprising (and unwelcome). Using this solved the problem but the yields were not a good.


a MS in org chem and a job in Pharma R&D
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  • α-SiO2 answered 3 years ago
    I thought Facts Matter's answer was reasonable (and certainly didn't deserve a thumb down). I knew with Me3N you get the crystalline adduct Me3N:→AlCl3. Jon's answer also seemed reasonable so I decided to do some research on the topic.
    N. N. Greenwood, A. Earnshaw, Chemistry of the Elements 2nd ed. (1997) p 234:
    "The adduct AlCl3.3NH3 has been shown by X-ray diffraction analysis to consist of elongated ovtahedra [AlCl2(NH3)4]^+ and compressed octahedra [AlCl4(NH3)2]^- ....."
    F. A. Cotton, G. Wilkinson, C. A. Murillo, M. Bochmann Advanced Inorganic Chemistry 6th ed (1999).
    p 185:
    " The ammonia complex AlCl3(NH3)2 has the structure [AlCl2(NH3)4]^+[AlCl4]^-.
    It is highly probable based on Co(III)(H2O) chem (conjugate base mechanism) and liq NH3 and amides in general that the following equilbrium exists:
    [AlCl2(NH3)4]^+ + NH3 ⇋ [AlCl2(NH3)3(NH2)] + NH4^+
    and it is [AlCl2(NH3)3(NH2)] that is the active reagent in the amidation rxn. I suspect AlCl3/NH3/toluene is a bit of a dog's breakfast that you can't study easily (no nice NMR handles).
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  • Facts Matter answered 3 years ago
    A simple Lewis acid - Lewis base reaction:

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  • Wendell Berry answered 3 years ago
    (I think) :)


    A guess from my GCSE level understanding of chemistry
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