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Author: Subject: Solubility of iodine in dichloromethane
Boffis
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[*] posted on 2-8-2020 at 05:25
Solubility of iodine in dichloromethane


Does anyone know how soluble iodine is in dichloromethane? I have searched on google etc and found a lot of data for benzene, toluene, carbon tetrachloride etc but not DCM. It is clearly pretty soluble >100g/L but how soluble.
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[*] posted on 2-8-2020 at 15:54


Quote: Originally posted by Boffis  
Does anyone know how soluble iodine is in dichloromethane? I have searched on google etc and found a lot of data for benzene, toluene, carbon tetrachloride etc but not DCM. It is clearly pretty soluble >100g/L but how soluble.



Solubilities of Organic and Inorganic Compounds, Volume 1: Binary Systems, Part 1, p 626, 1963.

I2-DCM.PNG - 17kB
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draculic acid69
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[*] posted on 2-8-2020 at 18:53


I have another thread exactly the same.apparently it's not very soluble at all
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[*] posted on 4-8-2020 at 09:59


The reason that iodine wouldnt be soluble in DCM is because Chlorine is much smaller and more electronegative, right? So that means the solute will have a much higher affinity for the chlorine as compared to the iodine. Let me hear your feedback so I can mark this as a learning experience.



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draculic acid69
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[*] posted on 4-8-2020 at 19:40


I've no idea about that but chloroform seems to dissolve iodine well so it's surprising that DCM isn't the same
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[*] posted on 5-8-2020 at 15:17


The dielectric constant of DCM is 8.93 while chloroform is at 5. I don't think polarity would play a big factor as to why DCM doesn't dissolve iodine as well. However after giving it much thought, perhaps it's the relationship between the opposing bonds of the DCM that makes it unreactive. The chlorines will always align themselves opposite from one another when bonded to the carbon. Thus, the chlorine bonds in DCM should be vibrating at a different frequency as compared to chloroform. These opposing chlorine molecules will vibrate with respect to one another. Taking a look at chloroform, there's three chlorine molecules and a hydrogen. Thus, there will be more steric hinderance and the bonds will vibrate in a more unstable fashion.

Therefore I propose the linear relationship between the chlorine molecules stabilize the molecule of DCM due to the bonds being able to vibrate at a higher frequency. On the contrary, the trichloromethane will have bond bending due to the steric clash between the three chlorine molecules. The inductive pocket that the three chlorine molecules create may perhaps be the reason that Iodine is able to be dissolved by chloroform. The lack of this inductive pocket in DCM prevents the Iodine from reacting.




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[*] posted on 5-8-2020 at 16:40


Quote: Originally posted by ThoughtsIControl  
The dielectric constant of DCM is 8.93 while chloroform is at 5. I don't think polarity would play a big factor as to why DCM doesn't dissolve iodine as well. However after giving it much thought, perhaps it's the relationship between the opposing bonds of the DCM that makes it unreactive. The chlorines will always align themselves opposite from one another when bonded to the carbon. Thus, the chlorine bonds in DCM should be vibrating at a different frequency as compared to chloroform. These opposing chlorine molecules will vibrate with respect to one another. Taking a look at chloroform, there's three chlorine molecules and a hydrogen. Thus, there will be more steric hinderance and the bonds will vibrate in a more unstable fashion.

Therefore I propose the linear relationship between the chlorine molecules stabilize the molecule of DCM due to the bonds being able to vibrate at a higher frequency. On the contrary, the trichloromethane will have bond bending due to the steric clash between the three chlorine molecules. The inductive pocket that the three chlorine molecules create may perhaps be the reason that Iodine is able to be dissolved by chloroform. The lack of this inductive pocket in DCM prevents the Iodine from reacting.


Chloroform simply has a lower dipole and stronger London forces, so it interacts with the iodine molecules more attractively. It has nothing to do with vibrations.

The chlorines aren't linear in DCM- it's a tetrahedral molecule.




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[*] posted on 5-8-2020 at 19:01


I understand that it's a tetrahedral molecule. Both of these molecules are. However, there is hydrogen replaced for a chlorine when talking about DCM. I am referring to the linear relationship amongst the two chlorine and two hydrogen atoms. There is more symmetry in this molecule. When talking about chloroform, there are still mirror planes but not the same ones. The rotation axis are also different. It would be a C3 instead of a C2 in the DCM. Not to mention, the chlorine atoms are electron withdrawing groups. Thus, there would be different vibrations in the bonds of chloroform because it has three chlorine atoms instead of the two in DCM.

https://www.chemtube3d.com/sym-c3vtrichloromethane/

Check out this link. There should be an inductive effect right in between the three electronegative chlorine molecules, I think. The ionic bonds should form a pocket with a vector going right in between the bottom of the three chlorine molecules, right?

This is what my hypothesis is about. There should be a stronger pull due to inductive effects in trichloromethane as compared to DCM.




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[*] posted on 5-8-2020 at 21:00


Hmmm....let's see.

The solubility of iodine, according to Eddie Current's source, is 58.6 g/L of dichloromethane. The density of dichloromethane is 1.33 g/mL, so that works out to be 4.4 g I2 per 100 g DCM.

Let's compare this to some other solvents, which we can find on chemister.ru (http://chemister.ru/Database/properties-en.php?dbid=1&id... ) All values in g I2 per 100 g solvent.

1,2-dichloroethane 5.43
Chloroform 3.09
Carbon tetrachloride 2.9
Carbon disulphide 20.4
Ethanol 27.2
Ethyl acetate 15.7
Diethyl ether 30.4
Bromoform 7.7
Bromoethane 14.6
Benzene 16.4

So iodine is MORE soluble in dichloromethane than chloroform or carbon tetrachloride (despite my attempted explanation about stronger London forces in the latter). it's not a simple relationship with polarity, or carbon disulphide and benzene (absolutely nonpolar) and ethanol (very polar for organic solvents) would not both be better solvents than dichloromethane. It's also not purely London forces, or bromoform wouldn't be such a poor solvent for it.

Or maybe the numbers would show a more obvious trend if we did the math to convert them all to mole fractions?




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[*] posted on 8-8-2020 at 04:55


Thank you guys for the discussion and the data. The high solubility in ether looks promising I just have to find out how soluble C2I2 is in ether and I'm away! That is presuming that niether diiodoacetylene nor tetraiodoethylene form association complexes with ether.

I am currently running the reaction between diiodoacetylene and iodine in 1,2-dichloropropane because it has a fairly high Bp (c 95 C) in which the product is sparingly soluble but the acetylene derivative is very soluble. So as the iodine dissolves in the hot mixture the sandy coloured crude tetraiodoethylene precipitates.

Interestingly the solubility of iodine in DCM clearly increases dramatically as you approach its boiling point of thew solvent.
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[*] posted on 8-8-2020 at 06:04


The most interesting one is the 'solubility' in THF. If you try to make a saturated solution it keeps going, and going, and going. When you hit about 50:50 you think to yourself, "What's going on here?" and you look it up and find out you're ring-opening the molecule and making all sorts of strange polymers in the process. What I have wondered and never checked though is how much free iodine is still available at that point.

Another thing to point out though is that iodine dissolves differently in different solvents giving different solvated species which can have different reactivities. A haexane solution is a beautiful purple from the elemental iodine being cradled nicely in there whereas an ether solution ends up being more reddish as it is complexed.




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[*] posted on 8-8-2020 at 09:59


https://www.sciencedirect.com/science/article/abs/pii/S00143...

According to my source, iodine is a recoverable catalyst that may be being used in industry right now for THF ring openings. So, at the point when you're halfway done you would have the same amount of iodine as you started with since it's just an intermediate step in the reaction. I've never played around with polymers myself yet but that sounds like a fun story.

I found this online because I was curious why the ether solution was red.
"The presence of peroxide in old samples of ethers may be detected by shaking them with freshly prepared solution of a FeSO4 followed by addition of KSCN. Appearance of blood red color indicates presence of peroxides."

The iron complex is what gives it the color right? The other atoms aren't as important in giving it the color or am I wrong?




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[*] posted on 8-8-2020 at 11:10


The peroxides will oxidize Fe(II) to Fe(III); the latter will complex with thiocynate to give the blood-red colour.



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