Newton2.0
Hazard to Self
Posts: 63
Registered: 12-8-2019
Member Is Offline
|
|
Activating metals post-addition
I am performing a reduction of benzoin to deoxybenzoin using Zn grains in GAA. The issue I am facing is that I have forgotten to activate the Zn
grains. I fear the oxide layer prevents the reduction from occurring so I am wondering if it is possible to activate the Zn in situ.
I am wondering if I can add a small amount of HCl to the reaction without damaging the product.
Has anyone had this problem?
|
|
|
njl
National Hazard
Posts: 609
Registered: 26-11-2019
Location: under the sycamore tree
Member Is Offline
Mood: ambivalent
|
|
I would first take a smaple of your reaction mixture, add HCl, and look for any change. Some reactions like this are sensitive to different acids. To
address your question, yes, HCl is added sometimes to activate metals in situ. However I would expect the GAA to attack the oxide just as well albeit
more slowly.
Reflux condenser?? I barely know her!
|
|
|
Newton2.0
Hazard to Self
Posts: 63
Registered: 12-8-2019
Member Is Offline
|
|
I do worry that the HCl might attack any deoxybenzoin that forms, either lowering the yield or forming unwanted side products.
Normally the Zn is consumed within 1.5 hours or so when it is properly activated.
I will follow your suggestion and see how the reaction mixture reacts in small amounts. Based on that, I might add more HCl in dropwise. I may also
just have to run the reaction longer or perhaps add additional GAA? So much to learn from this!
Thanks for responding!
|
|
|
zed
International Hazard
Posts: 2284
Registered: 6-9-2008
Location: Great State of Jefferson, City of Portland
Member Is Offline
Mood: Semi-repentant Sith Lord
|
|
A crystal of Iodine?
|
|
|
njl
National Hazard
Posts: 609
Registered: 26-11-2019
Location: under the sycamore tree
Member Is Offline
Mood: ambivalent
|
|
Zed I was thinking that too but I'm not sure by what mechanism it would help here. In Grignard reactions it's just turning the aklyl halide reagent
into a more active alkyl iodide, right? When forming aluminum alkoxides it produces AlI3.
Reflux condenser?? I barely know her!
|
|
|
digga
Harmless
Posts: 44
Registered: 11-6-2018
Member Is Offline
|
|
I have seen people use a tiny amount of iodine or a mercury salt to remove passivation in situ. Would use the former before the latter.
|
|
|
zed
International Hazard
Posts: 2284
Registered: 6-9-2008
Location: Great State of Jefferson, City of Portland
Member Is Offline
Mood: Semi-repentant Sith Lord
|
|
Mechanisms are not always certain. We often do things, because they work. Why they work, is subject to debate.
|
|
|
FragranceLover89
Hazard to Self
Posts: 72
Registered: 13-8-2019
Member Is Offline
|
|
Have you tried using ammonium chloride with tetrahydrofuran? Tetrahydrofuran forms a unique complex with Zn that allows it to reduce Diketones.
|
|
|
mr_bovinejony
Hazard to Others
Posts: 130
Registered: 20-4-2018
Member Is Offline
Mood: ASS
|
|
Hcl won't do anything to the reaction. I reduced benzlin with tin and hcl and it worked just fine
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
