# Copper (II) Acetate from 5% vinegar + salt, electrochemically

I'm trying to create Copper (II) Acetate crystals, but in these times of Coronavirus it's difficult to come by hydrogen peroxide. I could be patient, but I'm not, so I'm trying to make it electrochemically. I have 5% vinegar and lots of copper scrap, and an adjustable power supply. Unfortunately I can't barely get any current going, so I've thought of adding salt, regular NaCl. I'm curious what effect this will have on the final outcome though. Balancing equations is something I struggle with, but I'd really like to learn the chemistry here. Will the salt interfere with or alter the growth of the copper acetate crystals? Ultimately I'm trying to make calcium copper acetate crystals, I've already made the calcium acetate.

• Another ways is to let time and aerial oxygen to oxidate cupper, leading to copper acetate. $$\ce{4 HAc + O2 + 2 Cu -> 2 H2O + 2 Cu(Ac)2}$$ I once performed vinegar decalcification of aged boiling kettle. Its heating spiral had exposed cupper, with the stainless coating already mostly stripped away. I have shortly boiled vinegar and forgot it to let stay overnight. The solution got pretty blue. – Poutnik Mar 20 at 9:52
• Interesting. I thought about using a small air pump to bubble air through. As it is it's stood on a "hot plate" (coffee maker base wired to 20V DC, gets to about 200°F), with my small copper scrap in the bottom (lots of small pieces of 12 gauge solid wire). It's been about 12 hours and it's very slightly more blue than it was. I am impatient. – HaLo2FrEeEk Mar 20 at 9:56
• With NaCl, there is danger copper would end bound in $\ce{CuCl4^2-}$ – Poutnik Mar 20 at 10:01
• Welllll, all I had was a cheap 12v tire pump and some silicone tubing. I closed one end of the tubing and poked a bunch of needle holes in that end, then stuffed the other end into the tire chuck and applied 5v, to make it run a little more slowly. It's chugging along pumping a bunch of small bubbles through the copper. Not quiet, I probably won't leave it running, but it works! – HaLo2FrEeEk Mar 20 at 10:47
• I suppose forcing air must be much more efficient than heating, as heating expels oxygen from solution. – Poutnik Mar 20 at 10:50

To prepare copper acetate absence H2O2, employ a known method from hydrometallurgy to process copper ore employing aqueous ammonia, air (a source of oxygen) and a small amount of salt (acting as an electrolyte for this, in part, spontaneous electrochemical reaction detailed below). This results in tetra-ammine copper hydroxide. The latter exists only in solution and upon evaporation yields CuO (and possibly some Cu2O also, see this old patent). Add an acid of choice (like vinegar, a source of acetate) to convert CuO into copper acetate.

Related copper chemistry with ammonia and oxygen:

Cited half-reactions:

$$\ce{1/2 O2 + H2O + 2 e- -> 2 OH-}$$ (cathodic reduction of O2 at surface of the Copper)

And, at the Copper anode, the formation of the complex:

$$\ce{Cu + 4 NH3 + 2 H2O -> [Cu(NH3)4(H2O)2](2+) + 2 e-}$$ (anodic dissolution of Cu by a complexing agent)

With an overall reaction:

$$\ce{Cu + 4 NH3 + 1/2 O2 + 3 H2O -> [Cu(NH3)4(H2O)2](2+) + 2 OH-}$$

Also, some interesting cited standard chemical reactions, where copper oscillates between cuprous and cupric states as noted by the source below:

$$\ce{2 Cu + 4 NH3 + 1/2 O2 + H2O -> 2 [Cu(NH3)2]OH}$$

$$\ce{2[Cu(NH3)2]OH + 4 NH3 (aq) + 1/2 O2 + H2O -> 2 [Cu(NH3)4](OH)2}$$

$$\ce{Cu + [Cu(NH3)4](OH)2 <--> 2 [Cu(NH3)2]OH}$$

Reference: "Kinetics and Mechanism of Copper Dissolution In Aqueous Ammonia" and a related work detailing reactions: ‘Copper Dissolution in Ammonia Solutions: Identification of the Mechanism at Low Overpotentials’, which is also a fully available PDF.

Some alternate preparations would be to follow paths to copper patina (see this site, which discusses three paths for the home chemists which includes an embodiment of the ammonia prep, and, with the addition of vinegar, would convert the basic copper carbonate to copper acetate.

• Thank you, that's an awesome answer. I'll read more closely when I get home and I'm not on my phone, I think I have some 10% ammonia left from making ammonium sulfate. Thank you for the detailed information! – HaLo2FrEeEk Mar 20 at 22:13