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Author: Subject: Chloroform questions
Jackson
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[*] posted on 16-12-2018 at 14:27
Chloroform questions


Why is acetone used over isopropanol for making chloroform? Why does isopropanol not work as well?
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DraconicAcid
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[*] posted on 16-12-2018 at 14:54


With isopropanol, you have to use an extra equivalent of iodine to oxidize the alcohol to acetone.



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[*] posted on 16-12-2018 at 16:31


Why iodine



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[*] posted on 16-12-2018 at 17:06


Damn- thinking of the iodoform reaction. I just mean you have to use more oxidizer.



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Jackson
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[*] posted on 17-12-2018 at 08:09


Are more unwanted side products formed from isopropanol?

Would it be better to use calium hypochlorite from a pool supply store if using isopropanol to make chloroform. I cant find a source of acetone paint thinner and all the acetone nail polish removes have dyes that react with bleach to turn red and cause a very caustic smell.




Edited to add second question

[Edited on 12/17/2018 by Jackson]
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Sulaiman
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[*] posted on 17-12-2018 at 09:19


Quote: Originally posted by Jackson  
Why is acetone used over isopropanol for making chloroform?


In my case it was because acetone is easier and costs about the same as propanol via eBay (in my case uk, similar available via eBay USA)

Even though you may only want a little for your chloroform,
acetone is a very useful solvent.
After more than four years hobby chemistry I recently bought my first litre of propanol,
I'm on my third litre of acetone.

Reminder :
The reaction is very exothermic so use chilled dilute hypochlorite solution
or have lots of ice ready.




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Jackson
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[*] posted on 18-12-2018 at 08:40


Ive tryed running it with both. Both times i prechilled both the bleach and the isopropanol/acetone and mixted in an icebath. With the isopropanol it never produced a bottom layer of chloroform. Recently the formulation of acetone nail polish remover that is avaliable to me changed and no longer works. I was also having problems with the one time i did mske it because it seemed to form an emmulsion with the brine solutions i was drying it with.
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Nakhimov
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[*] posted on 18-12-2018 at 09:20


Haloform reactions proceed through a keto-enol tautomer, which requires a carbonyl (i.e., not an alcohol.) I'll provide a mechanism to explain if you're interested.
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Jackson
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[*] posted on 18-12-2018 at 10:09


Yes could you please.

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Jackson
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[*] posted on 18-12-2018 at 10:12


Quote: Originally posted by Nakhimov  
... I'll provide a mechanism to explain if you're interested.


Yes please




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[*] posted on 18-12-2018 at 11:45


I would expect a mechanism much like this: the reaction would presumably occur twice for each acetone molecule, and CO2 would be a byproduct.

https://imgur.com/a/1DpY0R9

Note that this explains a bit why the acetone precursor is preferable to isopropanol! It's that much easier for the carbonyl carbon to pull the electrons into the enolate form compared to the carbon on the alcohol.

[Edited on 12-18-2018 by Nakhimov]
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