woelen
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Separation of CHCl=CCl2 and CCl4
Some time ago, I received two very old and dirty bottles of chlorinated solvents. One of these bottles contains impure CCl4 and the other contains
CHCl=CCl2. The CCl4 was yellow and had a sweet smell, but also an unpleasant sharp smell was associated with it. The CHCl=CCl2 was colorless, but
contained a lot of flocculent solid matter, suspended in the liquid. I decided to clean up these chemicals and use distillation. The yellow color must
be some non-volatile organic contamination and the sharp smell could be some sulphurous compound (CCl4 in the past was made from CS2). I have no idea
what the flocculent solid is, it might be some stabilizer, which has deteriorated after so many years of storage in a dirty warm and dusty place.
I distilled both liquids, discarding the first 5% or so and left appr. 5% of the final volume, which has a deep yellow/brown color. This process gave
me a nice colorless and sweet smelling liquid, but I made a really stupid mistake  , I mixed up distilled CCl4 with distilled CHCl=CCl2. I poured the distilled CHCl=CCl2 in the bottle which already contained the distilled CCl4  . I now have around 400 ml of clear colorless liquid with a sweet smell and this liquid
is a mix of CCl4 and CHCl=CCl2. Their boiling points are really close and I see no way of separating them.
Any ideas what to do with this? I was really angry with myself, this is sooo stupid.
If no separation is possible, what interesting things can be done with the mix of these two chemicals? Is it still useful for anything chemistry
related, or is its only use reduced to degreasing and maybe as a non-selective general chlorinated solvent?
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Magpie
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Sorry to hear that you made such a mistake. This is easily done and I did the same when separating some coconut oil derived esters by distillation.
It seems the bp's are about 10C apart. A highly efficient fractionating column and a lot of patience should be able to separate them, assuming they
don't form an azeotrope, which is not likely I think.
Whether you want to do this or not depends on how badly you want to - CCl4 being rather rare and all.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Nicodem
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Quote: Originally posted by woelen  | | If no separation is possible, what interesting things can be done with the mix of these two chemicals? Is it still useful for anything chemistry
related, or is its only use reduced to degreasing and maybe as a non-selective general chlorinated solvent? |
I should check the literature, but perhaps it might be possible to use it for an acid catalysed alkylation analogously to what garage chemist
describes in his Synthesis of unsym.-heptachloropropane and hexachloropropene. Do you have any aluminium chloride?
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Magpie
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A more drastic approach might be to brominate or oxidize the alkene sacrificially, thereby allowing a more facile recovery of the CCl4.
The single most important condition for a successful synthesis is good mixing - Nicodem
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woelen
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I have AlCl3 anhydrous, but does that help in making heptachloropropane. The synth of Garage chemist is based on CCl2=CCl2 and CHCl3. I have a mix of
CHCl=CCl2 and CCl4. Indeed quite similar (an hydrogen atom is exchanged between the molecules), so I could give it a try, but I do not really expect
any results, because CCl4 is much less reactive than any of the other chemicals mentioned here.
Brominating the CHCl=CCl2 to make its boiling point much higher indeed is an option, but I doubt whether I am willing to sacrifice my precious bromine
for this. A lot of bromine is needed to do this bromination and from experience I know that bromination of CHCl=CCl2 is not that easy. It is a slow
reaction and may be hard to bring to completion.
Most likely I take my loss and try to find an application for this mix of chemicals.
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unionised
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Just a thought: Carbon tet will freeze in dry ice ( by quite a margin). Trike won't.
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Nicodem
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| Quote: Originally posted by woelen | | I have AlCl3 anhydrous, but does that help in making heptachloropropane. The synth of Garage chemist is based on CCl2=CCl2 and CHCl3. I have a mix of
CHCl=CCl2 and CCl4. Indeed quite similar (an hydrogen atom is exchanged between the molecules), so I could give it a try, but I do not really expect
any results, because CCl4 is much less reactive than any of the other chemicals mentioned here. |
Friedel-Crafts alkylations with CCl4 are known. I did a cursory literature search on the analogous reaction between CCl4 and
trichloroethene and found no conclusive evidence of what the major product would be. US3268603 describes the electrophilic addition to occur from the
less substituted side:
Cl2C=CHCl + CCl4 <=> Cl3C-CHCl-CCl3
It explicitly lists CCl4 as a suitable electrophile for this addition reaction on polyhaloethenes, but gives no example. Similarly, some
Japonese patents also claim the possibility of this reaction, but from the little I could understand from the schemes, the examples do not mention
this specific reaction (see JP4193841, JP4305542, JP4253928). In the examples, however, there are described the related reactions of CFCl3
on chlorofluoroethenes.
Edit: Nevermind. I found a reference where the reaction is described to give sym-heptachloropropane:
Journal fuer Praktische Chemie 1914, 89, 414-424; DOI: 10.1002/prac.19140890126
I believe you probably understand German enough to understand the article. I would have to struggle trough it to comprehend. Quoting from its CA:
| Quote: | | The following syntheses were carried out: CHCl3 + CHCl:CCl2 = CHCl2CHClCCl3; CCl4 + CHCl:CCl2 = CCl3CHClCCl3; CHCl3 + CHCl:CHCl = CHCl2CHClCHCl3; CCl4
+ CHCl:CHCl = CHCl2CHCl2CC; CHCl3 + CHCl:CH2 = C3Cl4H4; CHBr3 + CHBr:CHBr = CHBr2CHBrCHBr2. |
And here is another one:
J. Am. Chem. Soc. 1938, 60, 2491–2495; DOI: 10.1021/ja01277a059
Quoting from its CA:
| Quote: | | Cl2C:CHCl and CCl4 with AlCl3 at 20-30° for 48 h. give 49% of Cl3CCHClCCl3, b20 126-32°. |
A ratio of 520 g trichloroethene vs. 1220 g CCl4 was used (with 50 g aluminium chloride). After the workup, distillation at 20 torr is used
for the isolation of the product, so you can use an aspirator.
[Edited on 21/8/2012 by Nicodem]
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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woelen
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Thanks for these references. This looks very promising and I am willing to try this. I read the thread from Garage chemist and this heptachloro
compound would be a nice addition to my lab.
I can read German without any problems, but I cannot access the article. Is it possible for you to access them and make them available in the
references section?
This is a general problem for me. In the past (e.g. before the year 2000) many interesting articles were available from university websites as
postscript document, but nowadays you have to pay outrageous amounts of money for just a single article (e.g. EUR 30 or so) and sometimes the access
only is for two days or even one day. This is really bad.
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Nicodem
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| Quote: Originally posted by woelen | | I can read German without any problems, but I cannot access the article. Is it possible for you to access them and make them available in the
references section? |
Get them here.
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woelen
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Thanks very much!
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Formatik
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| Quote: Originally posted by woelen | I can read German without any problems, but I cannot access the article. Is it possible for you to access them and make them available in the
references section?
This is a general problem for me. In the past (e.g. before the year 2000) many interesting articles were available from university websites as
postscript document, but nowadays you have to pay outrageous amounts of money for just a single article (e.g. EUR 30 or so) and sometimes the access
only is for two days or even one day. This is really bad. |
Many volumes including that reference of Praktische Chemie is available at Gallica bnf for free. Check also hathitrust and archive.org, sometimes you
can find what you need there when it comes to old references.
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