Sciencemadness Discussion Board

Reaction between iodoform and chlorine

hkparker - 8-6-2011 at 14:39

I'm considering doing a YouTube video on Iodoform (synthesis, properties, etc). I've got the synthesis down but I was thinking about possible reactions and I'm wondering what would happen with chlorine. I would imagine chlorine would strip the iodines to make CHCl3 but wouldn't it also remove the hydrogen to make CCl4? Could be useful if it does! I'll be trying this by experimentation soon but I was wondering if anyone knew.

plante1999 - 8-6-2011 at 14:48

I dont think this will work , but it need a try . Take notte that the I2 will disolve in the chlorinated solvent.

hkparker - 9-6-2011 at 14:03

I did it. The reaction was quite exothermic and iodine was produced as well as a solvent. I would imagine this is CCl4. The iodine partly dissolved in the solvent and it was very very volatile.

Rogeryermaw - 9-6-2011 at 14:06

the extreme volatility certainly sounds like carbon tetrachloride. did it give off a sweet odor?

hkparker - 9-6-2011 at 14:10

I tried to smell it and I got a big wiff of extra chlorine, so I couldn't tell. By the time I got back it was all gone (it was sitting in the sun and I didn't make much). I will try this again and get a more accurate smell of it and idea of its physical properties.

So if this is CCl4 and I want to save it distillation would be hard as its contaminated with iodine. Im thinking I could add some mossy tin and react to form SnI4, that way when I distill there will be no more volatile products, sound good?

AndersHoveland - 9-6-2011 at 14:19

Quote: Originally posted by hkparker  

I was thinking about possible reactions with iodoform and I'm wondering what would happen with chlorine. I would imagine chlorine would strip the iodines to make CHCl3 but wouldn't it also remove the hydrogen to make CCl4?
I did it. The reaction was quite exothermic and iodine was produced as well as a solvent. I would imagine this is CCl4. The iodine partly dissolved in the solvent and it was very very volatile.


Did you do the reaction in water? That could greatly affect the outcome of the reaction. The chlorine disassociates in water to form hypochlorous acid and hydrochloric acid.
The iodine atoms would easily be substituted with hypochlorite. The intermediate would not be chemically stable, so likely formic acid would be the oxidation product.
Because iodine atoms have a larger diameter, they substitute out easily, whereas it is generally not feasible to substitute out chlorine atoms from an alkane because the reaction is so slow (months at room temperature, or an hour of refluxing with aqueous base)

You might try reacting dry chlorine gas with iodoform dissolved in chloroform, I would be somewhat surprised if there is a reaction (if there is a reaction I think you would only get chloroform and iodine chloride)
One interesting aspect of iodine chemistry, however, is that iodine is surprisingly reactive when it acts as a reducing agent. However, since iodine is itself generally an oxidizer, we generally do not encounter reactions were iodine acts as the reducing agent.

One suggestion, keep the reaction out of direct sunlight and do not leave the chlorine or iodine to stand with the other reactants for more than an hour. Alkanes can be halogenated by a free radical cascade mechanism, and this can obscure your results.

[Edited on 9-6-2011 by AndersHoveland]

Jor - 9-6-2011 at 15:03

You can test if it is CHCl3 or CCl4 by adding the liquid to warm sodium hydroxide solution, and let it stand. I don't know how long the reaction generally takes, but the chloroform will be hydrolysed to formate, and CCl4 will not react and will remain as the lower layer in the liquid. I however think you made chloroform, and not CCl4.

hkparker - 9-6-2011 at 15:06

thats a good test Jor, thanks. why don't you think the hydrogen was replaced with chlorine? just not enough reaction time/chlorine?

Jor - 9-6-2011 at 15:28

Because the radical reaction between chloroform and chlorine is very slow at RT AFAIK. I think it is possible to make CCl4 by bubbling chlorine into boiling chloroform under strong UV-irradiation, but the reaction is probably slow and unefficient. In industry it is done at high temperatures in the gas phase. When exchanging the halogens, I don't see why that hydrogen would somehow become 'activated'. But again I'm not sure so you should test it.
Did you simply lead chlorine over solid iodoform?
Also be sure to use a large excess of Cl2 or you might get partly chlorinated products (like iododichloromethane?).
And this would be a very expensive way to make CCl4, unless you can constantly recycle the I2 very efficiently and have loads of time.
But then I would try bubbling chlorine through strongly irradiated (blacklight) boiling chloroform. Or if you can get CS2, chlorinate and reduce that.
But I think this is purely an experiment to see what's happening and not to actually wanting to prepare CCl4 for later use? :P

hkparker - 9-6-2011 at 15:33

ok, that makes sense. I have read about making CCl4 from chloroform and chlorine but didn't realize it was at such extereme conditions. I led an excess of dry chlorine over solid iodoform and did consider that some partially chlorinated products could have formed so I was sure to use an excess. thanks for the help!

AndersHoveland - 9-6-2011 at 17:18

Quote: Originally posted by Jor  
I think it is possible to make CCl4 by bubbling chlorine into boiling chloroform under strong UV-irradiation, but the reaction is probably slow and unefficient. In industry it is done at high temperatures in the gas phase. When exchanging the halogens, I don't see why that hydrogen would somehow become 'activated'.


Leaving chloroform with dissolved chlorine in direct sunlight will very efficiently produce carbon tetrachloride. After only several hours, much of the chloroform will have reacted. Since it is a radical cascade mechanism, it only takes a single activating photon to cause the reaction of about 40 molecules. If I remember correctly, it requires a short wavelength, typically UV, although bromination can be done with blue-green light. Alternatively, vaporized chloroform could simply be heated to 400C with chlorine.

Actually, the hydrogen in chloroform might actually be somewhat 'activated'. Consider the rt reaction between chloroform and acetone to form "chlorobutanol".

Rogeryermaw - 9-6-2011 at 17:31

a boiling point analysis may also help if you can isolate the liquid. CHCl3 60o vs carbon tet at 76o.

hkparker - 11-6-2011 at 19:50

Gave it a try, and filmed it.

http://www.youtube.com/watch?v=OARF9IIeHVA

peach - 12-6-2011 at 01:40

Thanks for the video Hk!


[Edited on 12-6-2011 by peach]

hkparker - 12-6-2011 at 12:22

No problem!

woelen - 12-6-2011 at 13:10

Hmmm... I missed this thread on iodoform and chlorine. I already posted an experiment in the other iodoform thread, which is in the organic chemistry section. I repeat this post over here:

-----------------------------------------------------------------------

I have done a few experiments to check what happens with this reaction. I found it sufficiently interesting to make a small (text-only) web page about this experiment:

http://woelen.homescience.net/science/chem/exps/exppatt.cgi?...

The second experiment describes what happens when chlorine gas is passed over iodoform. Based on the results of this experiment I'm almost 100% sure that no CCl4 is formed, but only CHCl3 and possibly lower substitution products like CHCl2I and CHClI2.