TheNerdyFarmer
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Brown copper (II) chloride solution?
I have run into a bit of a weird discovery about the mixture of acetone and cupric chloride solution. I was initially making copper chloride via HCl
and H2O2 method and when I went to wash the beakers something interesting happened. I squirted some acetone in a beaker with a little cupric chloride
solution left in it and the results were interesting. It formed a quite turbid liquid and then quickly turned brown.
This may be a super common thing to happen among chemists but this has never happened to me before. Normally I rinse my beakers with water
first and then Finnish them with acetone.
Anyone know what is happening here? Is it a reaction taking place or is cupric chloride/acetone solution just inherently brown, if so, why?
I should also note that after this happened, I added water and it went nearly clear. Why does this happen? I cannot find anything online
about a reaction between copper chloride and acetone although I did find that cupric chloride is soluble in acetone and other alcohols. Did not see
anything about a color change though.
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JJay
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I've dissolved anhydrous copper (ii) chloride in dry acetone before... the solution was brown. I couldn't get the solution to react with aluminum,
though. I'm not sure if this was due to the passivating layer of aluminum oxide or some other reason, but I read a post a while back that mentioned a
copper (ii) chloride complex with acetone....
I didn't keep the solution around very long, but supposedly the acetone slowly reduces the copper (ii) chloride to copper (i) chloride, creating
chloroacetone in the process. Chloroacetone is a strong lachrymator and has been used as a war gas (although exposure is not usually fatal), so do be
careful. Lithium chloride is said to accelerate the chlorination of acetone by copper (ii) chloride... I'm not sure how water would affect it.
[Edited on 19-6-2017 by JJay]
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Σldritch
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The brown color is from anhydrous copper chloride. I guess the acetone dehydrates it.
It does not react with aluminium without water (at room temprature; thank you JJay  ) since it is needed for the reaction: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3565164/
[Edited on 18-6-2017 by Σldritch]
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JJay
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False. When you mix anhydrous copper (ii) chloride and aluminum and heat it, a reaction takes place: https://www.youtube.com/watch?v=0jHl2jVmR_g
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TheNerdyFarmer
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I kind of guessed that it was anhydrous cupric chloride due to the brown color but I did not think that acetone absorbed water that readily. Also, I
preformed this again. As I added more water, the solution turns a very light blue. Perhaps it rehydrates it? Thanks for the replies thus far!
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DraconicAcid
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I suspect that in the solvent of low polarity, the chloride displaces the water from the coordination sphere of the copper, and you get a tetrahedral
[Cu(H2O)2Cl2] complex, which is brown. Adding more water, either through Le Chatty's Principle or increasing the polarity of the solvent, favours
octahedral blue [Cu(H2O)5Cl]+ or [Cu(H2O)6]++ ions.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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