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Author: Subject: zinc-copper couple
chemrox
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[*] posted on 9-3-2016 at 16:04
zinc-copper couple


zinc-copper couple
How is this made?
I found a synth on acs but I don't have cupric acetate. I'm thinking this last is a pain to make

Attachment: jo01030a529Zn-Cu.pdf (403kB)
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ziqquratu
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[*] posted on 9-3-2016 at 17:04


That method makes a fairly active couple, but there are other simpler methods that work quite well. My favourite preparation, which I used extensively throughout my PhD work (for debromination of alpha-bromoketones), can be found in Org. Synth. 1961, 41, 72 (DOI: 10.15227/orgsyn.041.0072). It's not quite as reactive as the material made via the method you posted, but it's easier to prepare and is also better for large-scale preparations. The method below is my version based on that reference:

Zinc dust (9.81 g, 150mmol) was stirred vigorously for 1 min each with the following solutions: 1 M HCl (8mL × 4); water (20mL × 5); 2 % CuSO4(aq) (15mL × 2); water (20mL × 5); EtOH (20mL × 4); Et2O (20mL × 5). Following the final wash, the suspension was filtered, the solids washed with Et2O, collected and dried in vacuo.

Just to be clear, that's four successive washes of 1 minute each with 1 M HCl, and so on.

This method is quite easy, if a little tedious. Whilst you will lose some, take care not too pour off too much zinc when you decant the solutions (and also don't go to crazy extremes in decanting - you don't have to get every last drop, because you're washing it multiple times). When you put it in HCl, it should "fluff up"; once you start washing it goes back to being a fine powder. Once you get to the EtOH washes, it's a good idea to decant the solvent directly into a Buchner funnel, since it gets difficult to avoid pouring out quite a bit of the zinc dust at that point.

I stored my zinc-copper couple under inert gas, and it was usable for at least a month (I never made a batch big enough to last longer than that).
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DJF90
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[*] posted on 10-3-2016 at 05:00


If suitable you may be able to activate your zinc in situ using ethylene bromide and/or TMS-chloride. Use of an ultrasonic bath is also said to provide good results for activating zinc.

There are also other zinc couples that may be used (depending on your requirements). Please find excerpts from EROS attached.

Attachment: Zinc-Copper couple.pdf (114kB)
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Attachment: Zinc-Nickel couple.pdf (53kB)
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Attachment: Zinc-Silver couple.pdf (64kB)
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[Edited on 10-3-2016 by DJF90]
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chemrox
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[*] posted on 10-3-2016 at 13:14


Thank you both for these excellent refs!
@zig: is denatured EtOH acceptable for these washes? (EtAcO in EtOH)




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[*] posted on 14-3-2016 at 14:34


Sorry for the delayed reply chemrox.

I never tried it with denatured EtOH, but I can't see any major issues - if the denaturant is EtOAc I'd be quite confident that it would be fine (and fairly confident thinking of the other commonly used denaturants). The water is doing the main washing - removing excess copper or zinc salts or acid - whilst the EtOH is largely just displacing the water (then the ether displaces the EtOH and whatever residual water remains), so as long as the denaturant doesn't react it shouldn't interfere.
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