I am planning a reaction in which I iodate phthalic anhydride. My reaction is I2, phthalic anhydride, and copper(II) chloride as a catalyst. The solvent is 99.9% isopropanol. How do I separate the product (4-Iodophthalic anhydride) from the copper(II) chloride and remaining iodine?

Edit: I planned to boil away the solvent, and sublimate away the iodine from the remaining solid. How do I separate my product from the resulting mix? At the moment, I only have isopropanol.

  • 3
    $\begingroup$ I would recommend just running a normal flash column since you will likely have unreacted phthalic anhydride after running your reaction. If the reaction did have a very high yield (near 100%), a column may not be necessary. You could just add a bit of sodium carbonate to convert the iodine to sodium iodide, remove the isopropanol using a rotovap, and then use a separatory with methanol and ether (or hexane) to separate the salts (sodium iodide and copper chloride) from the product. $\endgroup$
    – Eli Jones
    Dec 28, 2020 at 2:21
  • $\begingroup$ I'm an amateur chemist, and I don't really have a flash column, so I can't really do that, but thanks for suggesting that. $\endgroup$
    – Jacob
    Dec 28, 2020 at 2:24
  • $\begingroup$ @Eli Jones: How does sodium carbonate reduce iodine to iodide? Sodium sulfite or sodium thiosulfate should do the trick. $\endgroup$
    – user55119
    Dec 28, 2020 at 3:45
  • $\begingroup$ Is there any concern that the isopropanol may open the anhydride? $\endgroup$
    – user55119
    Dec 28, 2020 at 3:49
  • $\begingroup$ @user55119 I agree that sodium thiosulfate would probably be better for neutralizing a bunch of iodine, but since only a small excess of iodine will be present, I read that sodium carbonate will convert iodine to sodium iodide and sodium iodate. I'm not sure how effective this is, so I can't guarantee this method, but it would probably be better than dealing with the messy sulfur byproducts using the other method. $\endgroup$
    – Eli Jones
    Dec 28, 2020 at 3:54

1 Answer 1


I just realized I can add sodium hydroxide, and filter off the resulting insoluble copper(II) hydroxide and sodium chloride, then boil down the result. If you can think of a better answer, feel free to suggest it to me.

  • $\begingroup$ The sodium hydroxide would probably destroy your phthalic anhydride (hydrolyze the anhydride moiety), and your product would still be contaminated with iodine and leftover starting material. $\endgroup$
    – Eli Jones
    Dec 28, 2020 at 2:25
  • $\begingroup$ Okay, then what should I do? I don't have any ether. Also, would sodium acetate work instead of sodium hydroxide? $\endgroup$
    – Jacob
    Dec 28, 2020 at 2:39
  • $\begingroup$ I just mentioned ether because it was a common nonpolar organic solvent. You could try something like gasoline, but I cannot guarantee how effective this will be. Also, be safe while removing your solvents from the product! Since you probably do not have fancy equipment, you should only use small amounts of solvent while outside and away from any open flames. $\endgroup$
    – Eli Jones
    Dec 28, 2020 at 4:03
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    $\begingroup$ I would recommend trying to use either sodium carbonate (you might have to heat the solution a bit for neutralization) or sodium thiosulfate. Sodium carbonate is sold commonly as washing soda, and sodium thiosulfate is also cheap and readily available. Sodium acetate might result in some transesterification of the anhydride. Also, I haven't read of sodium acetate being used to neutralize iodine. $\endgroup$
    – Eli Jones
    Dec 28, 2020 at 4:07

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