piogun
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reaction Cu/CCl4/DMSO (or DMF)
I came across the following description of an experiment (I translated it from Polish and it maight be a bit imprecise, but please be understanding):
Put 2-3g of Cu cut in small pieces( e.g. filings) and then pour 4-5ml of mixture of DMSO - (CH3)2SO and CCl4 1:1(V/V).
After several hours Cu is dissolved. If the mixture is heated up to around 50 Celsius degrees, the reaction becomes "stormy": the mixture
heates itself to boiling, the solution gets dark and during the reaction certain amount of gas is secreted (flammable, without smell). If the clear,
darkolive solution is left to cool down, greenish sediment appears consistiong of small cristals.If the mixture is poured into a considerable amount
of water, white sediment appears and the water solution gets greenish. This solution is strongly acidic and contains Cl- (reaction with AgNO3). White
sediment after trickling is gradually getting green during drying (CuCl?). White sediment is dissolved in water consisting ammonia, the solution is
dark and in the air is oxided to dark blue product - [Cu(NH3)4]2+.
Using DMF instead of DMSO gives the same result, but using CHCl3, CH2Cl2 instead of CCl4 gives negative result. The reaction with CCl4 is so intense
that the oxidation of Cu with oxygen from air and then complexing product of the oxidation, as it happens during "working" of water
containing ammonia on Cu with the access to air, may be ruled out. At first fromation of dichlorocarben (:CCl2) seems to be likely, but carbens
don't come into existence in such conditions. Such a great reactivity of CCl4 is also puzzling, as it's usually far less reactive than other
chloroderivatives of methane. And this with Cu which is also not very reactiove in similar processes. The role of DMSO or DMF may only be connected
with their great polarity which may make formation of appriopriate oxidating factor from CCl4 easier.
The author of this text asks at the end a few question which are also my questions. Here are they:
-What is this oxidating factor?
-Why don't the rest of chloroderivatives of methane react like CCl4?
-What is the role of polar solvent?
-What is the gas forming in the reaction?
-What is the product of reduction?
I hope it's understandable. Please answer as soon as possible.
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BromicAcid
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I would think that carbon tet would be necessary in that the other halogenated deivatives of methane CH3Cl, etc. Would react along different pathways
before they could react in an anologous manner due to their less sterically hinderedness.
Being that the gas has no smell I would think it would automatically point to hydrogen from reaction with the solvent, I would not believe that the
solvent is inert in these proceedings.
Possibly one of the oxidizing agents could be carbonyl chloride?
It does sound like a fun reaction though, too bad I don't have any CCl4 due to enviormental constraints 
Edit: I was thinking about it some more and analogous reactions. The reaction of carbon tetrachloride with H2O at high temp with transition metal
catalysts yeild COCl2 and HCl. Possibly heating CCl4 w/ the =O bond ruptures this, partially as a result of the transition metal catalyst. This
leads to the aforementioned carbonyl chloride which acts as an oxidizing agent leading to either CuCl or CuCl2 and CO (your odorless flammable gas).
The molecule that looses the oxygen either DMSO or DMF becomes chlorinated and might further act as an oxidizing agent or posses different properties.
Just some thoughts.
[Edited on 7/18/2004 by BromicAcid]
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piogun
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The reaction could also be the reaction of dehydrohalogenation of CCl4 which is recently being researched by lots of scientist. The most commonly
named catalysyt of the reaction is Pt on MgO, but it is said that metals like Ni or Cu may also catalyse the reaction. It also saays in the net that
the products of the reaction are CHCl3, CH4 and 1,1,2-trichloreethane and the more Pt was used the less 1,1,2-trichloroethane yielded.
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unionised
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How do you dehydrohalogenate something with no hydrogen in it?
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piogun
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You're right. Sorry, it should be dehalogenation.
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