Sciencemadness Discussion Board

Chlorination of DCM

Hexavalent - 23-3-2012 at 14:30

Could not find any information on this anywhere, so here goes. Would it be possible, under the right conditions, to chlorinate dichloromethane to chloroform and that to carbon tetrachloride?

barley81 - 23-3-2012 at 15:29

http://en.wikipedia.org/wiki/Chloroform#Industrial_routes

That is how chloroform is made. Methylene chloride, chloroform, and carbon tet are all produced by the chlorination of methane or methyl chloride (DCM should also work because it is an intermediate in the reaction) at 400˚C (according to Wikipedia). Doing that is not very practical for anything but industry. Luckily, chloroform can be made easily using the haloform reaction.

Edit:
Under UV light it may be feasible. You would need to regulate flow carefully, and have a strong UV source. Why do that when you can just buy chloroform and carbon tetrachloride (although it's hard to get carbon tet)?

[Edited on 23-3-2012 by barley81]

weiming1998 - 23-3-2012 at 15:29

Yes it would be possible, as in the reaction between methane and chlorine, chloroform and carbon tetrachloride is formed, instead of just methyl chloride and dichloromethane. But to chlorinate dichloromethane, the reactants must be either
.Heated to several hundred degrees
.Under strong UV light

BromicAcid - 23-3-2012 at 17:00

Did some work several years ago chlorinating tetrachloroethylene and trichloroethylene in an attempt to make carbon tetrachloride (which or course involved scission of the C-C bond). I attached a photo of the apparatus made by using a wooden salad bowl with UV LEDs inserted into it in regular intervals. The hole in the top was the prefect size for the neck of the flask into which I was leading my chlorine gas. It worked better than I expected despite the propensity of Pyrex glass for blocking UV as well as the low output of LED UV lights (there is a separate post on this forum regarding this). Part of the efficacy however was likely due to a small amount of catalytic iodine added at the start of each reaction forming the iodine monochloride insitu which is more aggressive in chlorination.

Just a word of advice, if you make such an apparatus resist the desire to look directly at it. Despite its beauty it will work hard to kill your vision just as it works hard to form radicals from your diatomic chlorine.

uv.jpg - 51kB

peach - 23-3-2012 at 18:44

:D Love it bromic!

Hex, you may want to make chloroform via the haloform instead, which is the way a lot of people do it. There are many videos on youtube, some of which are from the members here.

Magpie - 23-3-2012 at 19:06

This should be helpful:

http://www.sciencemadness.org/talk/viewthread.php?tid=1424&a...

Hexavalent - 24-3-2012 at 04:16

Yes, yes . . .I always make my chloroform via the haloform reaction, as it is much cheaper, I was just speculating about the reaction. The thing is, my dad doesn't like bottles of potential anaesthetics in the garage, so I always label it 'trichloromethane' and my diethyl ether as 'Et2O':)

garage chemist - 24-3-2012 at 04:31

Bromic, did that apparatus ever produce any isolatable CCl4?
I would think that adding chlorine to C2Cl4 would first make hexachloroethane and solidify the reaction mixture before further reaction. What were your observations?

Hexavalent, I'd recommend that you try out chlorination of DCM with chlorine in sunlight using catalytic iodine and a reflux setup.
An old german chemistry book gives a preparation of CCl4 from CHCl3 and chlorine under these conditions.

Hexavalent - 24-3-2012 at 05:05

Thanks, I will try that. Can you provide a link to the book with the instructions in it?

I cannot read German, but can get my teacher at school to translate:)

garage chemist - 24-3-2012 at 05:20

I posted that preparation here:
http://www.sciencemadness.org/talk/viewthread.php?tid=14927#...
Nobody on this board has attempted it properly before. You can be the first to do so.

Hexavalent - 24-3-2012 at 05:33

Thanks, I assume that with the correct stiochiometry you could make the chloroform from the DCM as opposed to going straight to the carb.tet. . . ??

garage chemist - 24-3-2012 at 05:37

That probably won't work well, you will always get a mixture of products. If you pass 1 mole of Cl2 into 1 mole of DCM and ensure that all of it reacts (which is most likely impossible) you will get a mixture of DCM, CHCl3 and CCl4.
Don't try to use stochiometric amounts of chlorine, you will need an excess since the evolving HCl gas will invariably carry a large amount of unreacted chlorine with it.

BromicAcid - 24-3-2012 at 06:27

Garage Chemist,

When I tried to distill the mixture I did get a small fraction coming over at the proper boiling point for carbon tetrachloride. However the experiment overall was a failure. After the fact I realized I had been too aggressive with how much material I was trying to chlorinate and I had added too little chlorine. Still, being a radical reaction it was all over the place giving all the products of the rainbow. The mixture did not become thick but did begin to precipitate crystals. Attached is a picture of the mixture after I filtered it and before distilling it. Crystals again precipitated out after filtering so the liquid must have been saturated with the hexachloroethane.



hexachloro.jpg - 41kB Setup.jpg - 110kB

Edit: Wow... this was 7 years ago...

[Edited on 3/24/2012 by BromicAcid]

Hexavalent - 24-3-2012 at 07:35

Thanks for that, I might try it soon, modified based on your experiences. Where can one acquire UV LEDs cheaply?

Sedit - 24-3-2012 at 07:51

What about using something like TCCA as the Chlorine source as it should be easier to handle the gaseous Chlorine.

barley81 - 24-3-2012 at 08:02

@Hexavalent:
Radioshack sells 'em. Alternatively you can buy some from eBay.
<a href="http://www.ebay.com/itm/100-x-5mm-Bright-UV-Purple-5000-mcd-LED-Bulb-Light-/150784833665?pt=LH_DefaultDomain_0&hash=item231b79f881">Prett y good deal.</a> A hundred of them for five dollars. Shipping might be slow from Hong Kong.

BromicAcid - 24-3-2012 at 08:37

There is an interesting article on light and chlorination here:

http://www.faizkaskar.8k.com/light1.html

Magpie - 24-3-2012 at 08:48

And here is some more experience for your perusal:

http://www.sciencemadness.org/talk/viewthread.php?tid=1305&a...

Agecer - 27-9-2012 at 03:21

Quote: Originally posted by BromicAcid  
Did some work several years ago chlorinating tetrachloroethylene and trichloroethylene in an attempt to make carbon tetrachloride (which or course involved scission of the C-C bond). I attached a photo of the apparatus made by using a wooden salad bowl with UV led tube inserted into it in regular intervals. The hole in the top was the prefect size for the neck of the flask into which I was leading my chlorine gas. It worked better than I expected despite the propensity of Pyrex glass for blocking UV as well as the low output of LED UV lights (there is a separate post on this forum regarding this). Part of the efficacy however was likely due to a small amount of catalytic iodine added at the start of each reaction forming the iodine monochloride insitu which is more aggressive in chlorination.

Just a word of advice, if you make such an apparatus resist the desire to look directly at it. Despite its beauty it will work hard to kill your vision just as it works hard to form radicals from your diatomic chlorine.



Will they not cause any harm?

[Edited on 28-9-2012 by Agecer]

kristofvagyok - 27-9-2012 at 09:41

Wow, this thead looks like an awesome project.

The lab where I work some cubane have been produced and one of the step were made under UV light, with an UV reactor. It was simple, a mercury vapor lamp was placed in a reactor and the borosilicate glass was removed from it, the inner quartz tube was shining in the mixture. It produced a lot heat (more than 100W), so the reactor was cooled with a lot water but it worked.

I would think that a reactor designed similarly to this would work great for this reaction also. A few mW LEDs are not so powerful...

Is there anyone who want to buy something from quarts glass? We've got a lot and they are currently used for... Nothing.

P.S: CCl4 is toxic as hell, don't forget it.

mr.crow - 27-9-2012 at 10:52

I don't think LEDs are going to cut it. They are more like blacklights for glow-in-the-dark minigolf

Putting the bulb in the flask is a good idea (despite the heat). Glass blocks a portion of the UV, that's why they use it for the outer envelope of high power bulbs

Check out Prepublications for a UV chlorination done by len1

Also watch out for phosgene