DrNoiZeZ
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Diiodomethane by Finkelstein
For three times I tried to get diiodomethane using the acetone method with ridiculous yields (if someone could get with 60% please let me know). The
Voguel's method with arsenite and iodoform works but it is dangerous (arsenite is poisonous) and iodoform is VERY expensive.
So, for the last time I tried the Finkelstein again but that time using DMF and it works!
In a tritubulate flask with very good reflux condenser and a thermometer 100 ml DMF (don't need to be anhydrous) is mixed with 120g NaI and 30g DCM.
The mixture becomes warm and the temp rises to 60 celsius in 15 mim. Then heat is applied and let it reflux for one hour. The color changes to yellow
and then to brown and there was a NaCl precipitate. At that point the temperature was 145 celsius and I stopped the reaction by cooling it and then
adding 300 ml of water. The brown bottom layer was separated and the yellow water fase was extracted with 3x100 ml DCM. All DCM extracts and the
brown layer were mixed and washed twice with 100 ml 5% thiossulfate in water ( to get rid the DMF and iodine), dried with MgSO4 and then rotovap to
eliminate the DCM. The residue was vacuum distilled (oil bath at 105 cesius) and the fraction at 80 celsius/20 mmHg was collected.
I did it three times and the results were around 65 to 70g each with a yield around 68,7%.
I hope it can be usefull to someone too
[Edited on 1-2-2012 by DrNoiZeZ]
[Edited on 1-2-2012 by DrNoiZeZ]
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turd
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Well done! You should state if the yield is based on DCM or NaI. Only for style reasons - it doesn't make lots of difference, since you only used ~10%
excess of NaI.
Did you come up with that yourself or did you get an inspiration from a Chinese patent that details a very similar approach? I pondered doing that in
an autoclave but then didn't bother, since one can buy CH2I2 for separating minerals by the flotation method...
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DrNoiZeZ
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Thanks
The yield was calculate based on DCM (0,353 mol)
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DrNoiZeZ
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No, I tried using DMF in real despair because I need CH2I2 and here it is difficult to find and expensive. After I tried I searched a little and found
few information of using DMF but almost everywhere you find the information of using acetone
I think acetone can work on a closed flask because the low temperature of reflux but I don't like to heat things that way.
[Edited on 1-2-2012 by DrNoiZeZ]
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