redfish
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Copper Acetate Synthesis
Hello, everybody. This is my first post on the forum, so I will begin with an introduction.
I am a high school student with extremely limited access to... well, everything. While it is true that this is mostly due to the fact that I am too
lazy to go out and get anything, I accept the challenge that absolute DIY presents. By "absolute DIY", I mean that I make EVERYTHING myself out of
what is available, usually for culinary, first-aid, or general purposes. I own no labware- I salvage model paint jars, perfume tubes, pizza sauce
jars, tin cans, tabasco sauce bottles, etc. for use in my chemical endeavors. I use a gas range and candles as heat sources. I don't even have any
pipettes. Sure, I could buy some stuff, but I enjoy this challenge.
Now that you know where I'm coming from, I can explain WHY anybody would want to synthesize the target chemical, in this case Copper (II) Acetate. For
me, this chemical is an important starting point, as it is one of the only soluble chemicals I can easily synthesize without appreciably large
quantities of impurities such as sodium ions. Beyond that, it is a good source of Copper (II) ions and is a moderately strong oxidizing agent. This
was one of the first chemicals I synthesized, and is very easy for beginners to synthesize.
There are two ways to approach this. The first, my original method, is more roundabout and less efficient, but it works and offers more practice for
beginners. It is a three-part process. The second is more efficient and therefore should theoretically have a higher yield, although yields are fairly
high in general; it is a two-part process.
First method, part 1
You will need a copper anode (pipe works, I used foil from a Li-ion battery), a copper or graphite cathode, batteries and wire, a container that can
hold water, and water.
This part is pretty straightforward. Place the anode and cathode in the water, then hook up the battery's positive terminal to the anode and the
negative terminal to the cathode. The greater the surface area of the anode, the better; also, the closer the electrodes are, the faster the process
will occur.
You should see bubbles forming at the cathode. (Yes, this is Hydrogen gas, which is highly flammable and can be explosive but will generally only be
produced in small quantities during this procedure.) This procedure is almost virtually identical to hydrolysis, with a single minor difference. The
simplified equation for hydrolysis is:
2H2O(l)->2H2(g)+O2(g)
The simplified equation for hydrolysis with a copper anode is:
2H2O(l)+Cu(s)->H2(g)+Cu(OH)2(s)
The desired product from this reaction is the Copper Hydroxide, a light blue substance that forms on the anode and settles on the bottom of the
container. If you use foil like I did, bits may break off in the water as the metal is oxidized; these can be filtered off in part 2. Over time, the
hydroxide blackens as it decomposes into the oxide, CuO; this is also useable, so do not remove the black that forms. Some black CuO may also form on
the cathode, if a copper cathode is used; since this is a useable chemical, shake this off into the water if you want maximum yield.
You can let this evaporate, boil it down, or carefully drain off the water to obtain the hydroxide, or you could just leave it in the water if you
don't mind working with a more dilute solution in part 2.
First method, part 2
For this part, you will need the compounds formed in part 1, a sealable bottle or jar (an empty plastic disposable water bottle works fine), distilled
white vinegar (other vinegars could work, but would include more impurities), filters (optional), and a sink.
To begin this part, transfer the compounds formed in part 1 to a sealable container, and fill with vinegar. (It should be safe to use excess vinegar,
as it will evaporate with the water in the final concentration process.) The vinegar alone will not dissolve the hydroxide at room temperature; to
form the acetate, the mixture must be heated. A convenient way to do this is to run the hot water in a sink, fill the sink in hot water, and immerse
the container for a long time, changing the water occasionally. You should notice the solution becoming blue as you do this. Continue heating until
all of the copper hydroxide and oxide has dissolved, and the solution is clear when agitated. If this is not the case after an hour of heating, add
more vinegar if possible; if not possible, drain the solution (liquid) into another container and save, and then add more vinegar and continue
heating. If solid metal flakes remain, they can be filtered off using coffee filters; impurities introduced by the vinegar can be minimized by passing
the solution through an activated carbon filter.
Chemical equation for the reaction:
Cu(OH)2(s)+2CH3COOH(l)->2H2O(l)+Cu(CH3COO)2(aq)
and
CuO(s)+2CH3COOH(l)->H2O(l)+Cu(CH3COO)2(aq)
First method, part 3
This is the final part of the first method. For this part, you will need sealable plastic containers such as disposable water bottles and a freezer
and/or an evaporating dish or large shallow bowl and/or a heat-safe dish and heat source.
This part concentrates on concentration (please pardon the pun). There are three methods that can be utilized here: freeze concentration, evaporation,
and boiling. You may combine methods as you wish, but if a solid product is desired, I would recommend evaporation as a final step. Keep in mind that
copper acetate is not very soluble in water, so a surprisingly small amount of solid will crystallize out of solution.
Boiling and evaporation are fairly straightforward. I often use the clear flexible plastic that some things are packaged in as evaporating dishes.
When heating objects, make sure that you use a heat-safe container- I have broken many glass containers by heat contact, even if the heat source is
only a candle. When boiling or evaporating, just use common sense.
Freeze concentration is another method that I would like to point out to budding chemists. It is often neater and easier than boiling and evaporation,
and all you need is a freezer (or a cold climate) and a plastic bottle (water expands when frozen, so glass could shatter if used for this purpose).
You also need another container with a mouth wider than the plastic bottle, to transfer the concentrated liquid into. All you have to do is, fill the
plastic bottle about 3/4th's full of the solution, cap it, and stick it into the freezer. After a few hours, when it is completely frozen, take it
out, unscrew the cap (this can be difficult, so feel free to use as much force as necessary), invert it, and stick it into the larger-mouthed
container. The solution will melt faster than the water, and will drip into the container. This is the same method used when concentrating vinegar.
Note, however, that this does not work due to a lower melting point of the solute, but rather because of the nature of hydrogen bonds in aqueous
solutions of ionic or semi-ionic compounds.
Note that if you used excess vinegar in the creation of the copper acetate, it will likely be concentrated along with the salt after this part.
Therefore, be careful when handling the final product, as it can be quite acidic.
Second method, part 1
For this method, you will need distilled white vinegar, a copper anode, a copper or graphite cathode, a battery and wires for hookup, and a container
for the vinegar.
This part is nearly identical to part 1 of the first method, replacing water with vinegar. This is a much more efficient process. I noticed that more
CuO formed on the cathode when electrolysing vinegar than water, so you may want to obtain max yield by scraping this off and heating it in the
product solution, as in part 2 of method 1. However, this is not necessary, and will only slightly increase yield.
Second method, part 2
The final part of the second method is concentration. See part 3 of the first method.
Again, this is my first post so I could use some feedback.
Questions? Comments? Criticism?
[Edited on 1-1-2012 by redfish]
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Megak
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interesting, in my experience i've found electrolysis with copper electrodes to be tricky (with few exceptions).
What about this:
CuSO4 + 2CH3COOH -> Cu(CH3COO)2 + H2SO4
Though I doubt acetic acid would ever give up for sulfuric acid
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redfish
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Quote: Originally posted by Megak  | interesting, in my experience i've found electrolysis with copper electrodes to be tricky (with few exceptions).
What about this:
CuSO4 + 2CH3COOH -> Cu(CH3COO)2 + H2SO4
Though I doubt acetic acid would ever give up for sulfuric acid |
What do you mean by "tricky"? It's no different from electrolysis using any other metallic anode.
And although that seems like it would make sense on first glance, remember that we are talking about ions in aqueous solution, so it's not that
straightforward. You would just end up with Copper (II) ions, Hydrogen ions, Sulfate ions, and Acetate ions in solution. Besides, as I stated in my
"introduction", I wouldn't have any copper sulfate to begin with. It would, however, increase the acidity of the solution. If there aren't any threads
discussing why, I'd like to make one as it seems to be a topic of confusion (especially amongst high school chemistry students).
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theflickkk
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I've placed copper strips in a jar of acetic acid to make copper acetate. This method results in some small crystals of copper acetate forming around
the copper strips that are partially submerged in the solution. Easy way to make copper acetate albeit rather slowly.
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redfish
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| Quote: Originally posted by theflickkk |
I've placed copper strips in a jar of acetic acid to make copper acetate. This method results in some small crystals of copper acetate forming around
the copper strips that are partially submerged in the solution. Easy way to make copper acetate albeit rather slowly. |
Was the acetic acid you used glacial? I doubt this could happen using household vinegar, as copper is less reactive than hydrogen and therefore would
not be easily oxidized by a 5% solution of acetic acid.
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theflickkk
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Nope it was plain dilute acetic acid. Basically, artificial vinegar. I'm sure it works because i've done this many times. It takes a really long time
to get a good crop of crystals though. With this method, you can just leave the entire container somewhere safe and return to "harvest" the crystals
after some time (a long time actually).
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Chemistry Alchemist
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Ive got 2 videos of Copper Acetate Synthesis, both wih good yields... links are down below if you wanna check them out
Acetic acid, Copper, H2O2
http://www.youtube.com/watch?v=-aSaSe9x2E0&feature=plcp&...
Acetic Acid, Copper Carbonate
http://www.youtube.com/watch?v=znYJO7xa06s&feature=plcp&...
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redfish
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Thanks for the links, CA. The H2O2 and acetic acid method makes more sense to me, as the peroxide would aid in the oxidation of the copper, but I
suppose you could get the same result from just the acetic acid if you let it sit for long enough. I'll have to try it myself sometime.
As for the carbonate, that's a more basic acid-base reaction. How do you make the carbonate, though? (I could do it in reverse, by adding copper
acetate to a solution of sodium carbonate and collecting the precipitate, also producing the useful sodium acetate. But to use this to make more
copper acetate would be redundant.)
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Chemistry Alchemist
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I made my Copper Carbonate by adding Sodium Bicarbonate to Copper Chloride or Copper Sulfate... Link below
Copper Sulfate, Sodium Bicarbonate
http://www.youtube.com/watch?v=4_z0pZe9eWg
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entropy51
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Must you start a redundant thread instead of searching for, finding, and adding to one of the existing threads?
For example http://www.sciencemadness.org/whisper/viewthread.php?tid=111...
in which Woelen gives a very simple synthesis from copper sulfate, available in hardware stores as root killer.
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redfish
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Apparently you did not understand the purpose of this experiment. At the beginning of my post I explained that this procedure was designed so that any
lazy bum (like myself) could perform it without making any purchases, owning any equipment not found in a 1/2 bath, or using any chemicals that could
not be found in at least 90% of households.
I must admit that given this basis for this thread, it may have been more aptly created in the beginnings forum. However, since it deals with basic
learning techniques and complete reagent synthesis, I believe that a separate thread is merited.
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entropy51
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Well of course you did.
Better to remain silent and appear a fool than to open your mouth and remove all doubt.
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redfish
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Haha yeah, you probably could have taken that for granted. I've got two books to read and a chemistry lab to finish for school tomorrow, so I need to
redirect my attention towards my studies for now.
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Sciencevamos
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You also can pass an electric current threw an aqueous solution of calcium acetate(Vinegar+egg shells or chalk) with 2 copper electrodes.
A second alternative would be to mix an equal ratio of H202 and vinegar and add copper metal
Here is a link to a video:
http://www.youtube.com/watch?v=mOpxpoOemN0
Good luck!
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bfesser
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Thread Moved
8-2-2014 at 07:54 |
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