Sciencemadness Discussion Board

Organic copper salts

TheDude - 14-1-2019 at 20:36

I am a long timer lurker and citizen scientist, but lately I have gotten into something I figure might be of interest. I have been making copper salts with some organic acids that haven't been characterized well in literature as of late. I was making some salts to show to a friend's kids, and I realized that a lot of the easily made organic acid salts of copper weren't well documented.

Copper acetate was the first salt in my series of attempts and it is well documented, but when I moved on to citrate salts I was left with very little to go on. So I moved on to malic acid tonight and the solution took up a lovely blue color upon addition of basic copper carbonate. I don't know exactly what I formed but like previous compounds, I plan on attempting to crystallize it and testing dehydration and decomposition temperatures, as well as testing different stoichiometric mixtures to see if it changes the outcome.

If you guys are interested in the results or have any suggestions, I would love to know.

[Edited on 15-1-2019 by TheDude]

j_sum1 - 14-1-2019 at 21:05

Sounds like a great project. Please take photos and report back.

mayko - 14-1-2019 at 21:05

Welcome to the forum! It would be great to hear your experiences. I just bottled some copper formate, which has a really beautiful decomposition into copper metal. I also have a copper lactate solution which is drying.

There's some information about copper citrate in this thread:
http://www.sciencemadness.org/talk/viewthread.php?tid=62904

j_sum1 - 14-1-2019 at 21:40

https://www.sciencemadness.org/whisper/viewthread.php?tid=62...

This was the result of a copper chemistry competition. Not all of it is organic (obviously) but there are some good ideas in there as well as some results and photos. Copper aspirinate springs to mind but there are numerous others.

TheDude - 14-1-2019 at 22:35

Top is the arbitrary test mixture of malic acid and fairly crude basic copper carbonate.

The vials left to right are the dried but unheated precipitate from CuO being slowly added to slightly over 1M solution of citric acid and stirred until it dissolved. At ambient temperatures this took quite a while. An upscaled run which used heat, but below 100C to produce the product to the right, which was identical to the eye before I heated it in a dry beaker at ~120C based on a fairly cheap IR thermometer. I am assuming that the blue sample is anhydrous based on what I could find.

The next one is the CuO I used to make the previous two products. I first made Cu(OH)2 by reacting CuSO4 and NaOH in stoichiometric amounts, decanting off the supernate and washing the precipitate with stirring for just over 10min. I then decanted off the water and heated to dryness. I washed this with stirring in water overnight before filtering. I think this is as pure as I am likely to get for this given venture.

On the far right is my first attempt at copper(II) acetate from basic copper carbonate and acetic acid, I suspect it is somewhat contaminated or just finicky when it comes to growing larger crystals. I will repeat the process at a later date with more care.

I appreciate the links. I plan on repeating these under more controlled conditions shortly, my original plan was to make pretty colors for kids, I hadn't really planned on finding as much uncertainty as I have found. I will be trying to dehydrate and decompose at more well controlled temperatures first though.

Copper citrates oxide and acetate.jpg - 73kB

[Edited on 15-1-2019 by TheDude]

TheDude - 15-1-2019 at 00:28

Quote: Originally posted by j_sum1  
https://www.sciencemadness.org/whisper/viewthread.php?tid=62...

This was the result of a copper chemistry competition. Not all of it is organic (obviously) but there are some good ideas in there as well as some results and photos. Copper aspirinate springs to mind but there are numerous others.


I had planned on going to sleep after my previous post, but I fell down the rabbit hole reading through this. Much appreciated, I had missed this in my cursory searches before posting. Looks like I might have plenty to do until I get bored with copper.

j_sum1 - 15-1-2019 at 01:07

Haha.
That's what happens when you stop lurking.
Good luck getting back to normal life.

arkoma - 15-1-2019 at 15:47

Element 29 is my favorite

TheDude - 7-2-2019 at 21:04

So I have spent the past two weeks making a series of poor choices trying to purify my copper oxides. It would have been a much better idea to just buy some of known purity, but I am stubborn and was convinced that I could produce better than what was quickly and cheaply available, while I am certain that I did, it is still not as clean as I had hoped. In the end I ended up buying a pound of CuO just so that I would have two sources with different contaminants.

Now that I have quite a bit of CuO and basic copper carbonate, with a smaller amount of Cu2O, I am working on assembling some acids to test. I have some glacial acetic acid, malic acid, citric acid, tartaric acid, and acetylsalicylic acid on hand currently. I am in the process of making some salicylic acid as well. Barring the acetic acid, I plan on attempting to make new clean salts of each of these, but I have spent far too much time on this already to stop there. Do you guys have any suggestions for other organic acids to try to make salts from?

Any input would be appreciated.

Sigmatropic - 7-2-2019 at 22:20

I recently found out about copper salts of amino acids and their urea Complexes, I will give them a shot when the other two I'm working on are finished. Some pretty pictures, which got me on to the alaninate urea Complex https://m.imgur.com/gallery/5n2fyCn

Perhaps you could also try the amino version of copper salicylate, copper anthranilate.
Also have you considered double salts such as copper calcium acetate, I wouldn't be suprised if double salts form from other organic acids too.

j_sum1 - 8-2-2019 at 02:10

Love the imgur posts Sigma.

Sigmatropic - 8-2-2019 at 03:53

I should point out that those are not my pictures, unfortunately.

TheDude - 8-2-2019 at 08:26

Quote: Originally posted by Sigmatropic  
I recently found out about copper salts of amino acids and their urea Complexes, I will give them a shot when the other two I'm working on are finished. Some pretty pictures, which got me on to the alaninate urea Complex https://m.imgur.com/gallery/5n2fyCn

Perhaps you could also try the amino version of copper salicylate, copper anthranilate.
Also have you considered double salts such as copper calcium acetate, I wouldn't be suprised if double salts form from other organic acids too.


Thank you, I will definitely look into the amino acids, they hadn't even crossed my mind. I will look into double salts in greater detail, this is becoming a rather good learning experience.

Sigmatropic - 8-2-2019 at 09:07

Don't bother with copper anthranilate, it is simply too insoluble. Or at least for what I intend to use it for, growing a large single crystal.

I prepared it today by an adaptation of a procedure for the manufacture of anthranilic acid page 206-207

1 g of anthranilic acid acid was dissolved in 10 mL of 1 M NaOH, then carefully neutralized with acetic acid (note). There was then added a stoichiometric (half an equivalent) amount copper nitrate solution. A fine pale blue ppt formed immediately. The suspension was further acidified with acetic acid to dissolve possible copper hydroxides before the solids were filtered off. The filter cake was washed with water, then MeOH, then Ether to obtain copper anthranilate as a free flowing pale blue powder. This proved to be insoluble in boiling water and in boiling methanol. It did dissolve slowly in 1M HCl, presumably due to hydrolysis.

Note: pH 6-7, when the mixture is acidified with too much acetic acid, anthranilic acid starts to crystallize out of the mixture.

Suggestions as to check that this product is not in fact copper hydroxide or contains copper hydroxides? I believe that copper hydroxides form black copper oxide in boiling water, which I did not observe.

On heating over (not in) an open flame the product gives off some fumes, turns black and some embers form, suggesting to me the presence of carbon.

Also if there is a procedure where I'm unaware of by which to grow large single crystals of copper anthranilate, I'd be very interested in hearing.

[Edited on 8-2-2019 by Sigmatropic]

TheDude - 8-2-2019 at 10:00

Quote: Originally posted by Sigmatropic  
Don't bother with copper anthranilate, it is simply too insoluble. Or at least for what I intend to use it for, growing a large single crystal.


For my purposes this doesn't matter, unfortunately this project is my first attempt at piecing together a process of my own from literature, so I am probably not going to be very helpful to solve your problem.

I did however run a quick test of basic copper carbonate and glutamine, and something definitely happened, so I am going to clean out the magnesium stearate and do a more controlled attempt at getting something.

Sigmatropic - 8-2-2019 at 11:13

It seems they are generally prepared by buffering a solution of amino acid with an alkali acetate and treating it with a soluble copper salt (nitrate, sulphate, chloride and I presume acetate) (see attachment). Followed by slow evaporation,although I don't see why you can't precipitate them directly when you employ concentrated solutions.

It would be interesting to see how lysine and glutamic acid are different, need more buffering or less? Perhaps lysine and glutamic acid can form complexes in 1:1 ratio due to participation of the side chain residues.

Attachment: synthesis-characterization-of-some-complexes-of-copper-ii-with-lasparginine-lhistidine-llysine.pdf (596kB)
This file has been downloaded 380 times

DraconicAcid - 8-2-2019 at 11:24

Copper anthranilate is pretty insoluble- it's a good way to do quantitative analysis for copper. I've tried doing slow diffusion of the two reactants, and it hasn't worked to grow crystals. I did get some small crystals of it once- I think it was by reacting copper acetate and methyl anthranilate in a solution with copious amounts of acetic acid (which slowly hydrolyzed the ester). But it also turned black and crappy, so I didn't get much.

[Edited on 8-2-2019 by DraconicAcid]

DraconicAcid - 8-2-2019 at 14:21

Quote: Originally posted by Sigmatropic  
It seems they are generally prepared by buffering a solution of amino acid with an alkali acetate and treating it with a soluble copper salt (nitrate, sulphate, chloride and I presume acetate) (see attachment). Followed by slow evaporation,although I don't see why you can't precipitate them directly when you employ concentrated solutions.

It would be interesting to see how lysine and glutamic acid are different, need more buffering or less? Perhaps lysine and glutamic acid can form complexes in 1:1 ratio due to participation of the side chain residues.

This kind of paper bugs me, because I find it hard to believe that these amino acids will coordinate as neutral molecules rather than being deprotonated. I think they need to back up their structural claims better than they do.

A slightly older paper: http://www.jbc.org/content/13/1/1.full.pdf

[Edited on 8-2-2019 by DraconicAcid]

Lex - 8-2-2019 at 15:21

If you're not interested in growing crystals, mixing stoichiometric solutions of copper sulfate and oxalic acid results in a beautiful sky-blue precipitate of copper (II) oxalate.

Best of all you can do it in half an hour!

DraconicAcid - 8-2-2019 at 15:36

Quote: Originally posted by Lex  
If you're not interested in growing crystals, mixing stoichiometric solutions of copper sulfate and oxalic acid results in a beautiful sky-blue precipitate of copper (II) oxalate.

Best of all you can do it in half an hour!

You can add an extra equivalent of sodium or potassium oxalate and get the alkali bis(oxalato)cuprate, which would probably crystallize nicely with very slow cooling. (Although I usually get needles.)

TheDude - 8-2-2019 at 21:09

Sorry about the double post, not sure what happened.

[Edited on 9-2-2019 by TheDude]

[Edited on 9-2-2019 by TheDude]

TheDude - 10-2-2019 at 18:32

I ran across something I didn't expect when mixing basic copper carbonate and glutamine, a purple precipitate (pics below.) I initially just dumped capsules of a glutamine supplement into the beaker with a bit of water and basic copper carbonate in it, I noticed the precipitate but the magnesium stearate in the capsules made an absolute mess of things. I ended up making a saturated glutamine solution and filtering the scum off to make the sample I bothered to recover. Interestingly the supernate is colored similarly to what you would get if you had added aqueous ammonia instead of glutamine, it boils down to thick, very blue syrupy liquid.

https://imgur.com/v5UsLuk
https://imgur.com/6VX5VZS

The second image shows it next to the result of CuO and citric acid as seen in an earlier post, my phone seems to make things a bit more blue than they actually are. The precipitate is a rather rich lilac.

I have attempted to form a complex using copper(II) sulfate and glutamine and then raising the pH using sodium carbonate and bicarbonate, separately, but what precipitated was blue and not purple.

I also made fresh basic copper carbonate and without processing added my saturated glutamine solution to it and was able to get the purple precipitate again.

Lastly, I made up some copper(II) hydroxide, using a slight excess of sodium hydroxide, and without any further processing added a freshly prepared glutamine solution but only a tiny amount of solid appears to be present, and from what I can see it seems to be blue.

From what I can tell this seems to work reliably with basic copper carbonate, but I am unable to get it to work under other conditions where copper(II) ions are present. I tried to hunt down some literature on purple copper compounds and I did find a paper stating that "Sometimes Copper and amino acids form oxo complexes, which also feature copper(III) [1].
With di- and tripeptides, purple-colored copper(III) complexes are stabilized by the deprotonated amide ligands [2]."

https://www.researchgate.net/profile/Mohammad_Hakimi/publica...

Adding dilute HBr to a suspension of the purple substance in water resulted in a clear solution, similarly the same things happened with dilute and concentrated sulfuric acid. Sodium hydroxide had little or no effect.

I don't really know where to go from here. Is there any reasonable way to figure out what I have? Any advice would be greatly appreciated.

Edit: The glutamine added to copper hydroxide did precipitate a purple powder but it is very fine and took much longer to settle out.

[Edited on 11-2-2019 by TheDude]