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Author: Subject: Acid-catalysed halogenation
Filemon
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[*] posted on 26-7-2006 at 11:46
Acid-catalysed halogenation


I want to make iodoacetone:


acetone + I2---H+--> iodoacetone + HI

I need to know the exact details of the reaction. I will use acetic acid. The weak acids are better. How much acid concentration and temperature are optimum?

[Edited on 26-7-2006 by Filemon]

[Edited on 26-7-2006 by Filemon]
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guy
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[*] posted on 26-7-2006 at 12:17


Try glacial acetic acid and concentrated HI. CH3COOH + HI ---> CH3COI + H2O



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Filemon
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[*] posted on 26-7-2006 at 14:24


I believe that you have mistake. I'm not speaking acetic acid halogenation but acetone.
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[*] posted on 26-7-2006 at 14:45


Oh sorry

Why would you say weak acids are better?





[Edited on 7/26/2006 by guy]




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Filemon
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[*] posted on 26-7-2006 at 15:00


Excuse me. I have mistake. A strong acid is a catalyzed best.
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a123x
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[*] posted on 27-7-2006 at 15:02


I would only start with like a drop or two of strong acid catalyst. It should be all that's necessary to get things going and once the reaction starts, it produces more strong acid. I don't know what temperature is necessary though. I've done the alpha halogenation reaction with bromine and m-chloropropiophenone which was done at room temp with no strong acid catalyst added(allowing the reaction to start slowly to produce some HBr which then caused it to proceed more rapidly). Iodine is less reactive so you might need to heat gently or even reflux if the reaction doesn't proceed quickly by itself.
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not_important
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[*] posted on 27-7-2006 at 15:34


Remember that HI will reduce iodides and alcohols

ROH + HI <=> RI + H2O

RI + HI => RH + I2 (the reaction that might interfere for you)

I suspect that you will have better yields by making the chloro or bromo acetone, then treating it with a solution of NaI in acetone

RCl + NaI => RI + NaCl (ppt)

Note that the iodide should be anhydrous, as water will allow the NaCl to stay in solution; its precipitation is what drives the reaction.

Sodium bromide is slightly soluble in acetone, using the organic bromide may not give quite as good yields, or require an excess of sodium iodide.

You might be able to one-pot this by chloronating an excess of acetone will marble chips to scavange the HCl formed, then add finely powdered NaI or CaI2 and stir for a time.
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quantumcorespacealchemyst
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[*] posted on 22-1-2015 at 00:09


Quote: Originally posted by not_important  
Remember that HI will reduce iodides and alcohols

ROH + HI <=> RI + H2O

RI + HI => RH + I2 (the reaction that might interfere for you)

I suspect that you will have better yields by making the chloro or bromo acetone, then treating it with a solution of NaI in acetone

RCl + NaI => RI + NaCl (ppt)

Note that the iodide should be anhydrous, as water will allow the NaCl to stay in solution; its precipitation is what drives the reaction.

Sodium bromide is slightly soluble in acetone, using the organic bromide may not give quite as good yields, or require an excess of sodium iodide.

You might be able to one-pot this by chloronating an excess of acetone will marble chips to scavange the HCl formed, then add finely powdered NaI or CaI2 and stir for a time.


the neutralization of a carbonate with HCl will produce CO2 water and a chloride salt. perhaps a desiccant salt that hydrates can be used to keep the salts precipitated?
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Dr.Bob
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[*] posted on 22-1-2015 at 18:03


Also be aware that chloroacetone will burn your eyes, as it is a tear gas, so be careful how and where you run this reaction, as if you have any leak into the neighborhood, you might have people calling in a gas leak or the police. And you may be crying too hard to control the reaction.
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