Planning a simple radical bromination with NBS in DCM w/ hv using a slight (10-15 mol% or so) excess of NBS. The product is unstable to bases,
although a quick dilute NaHCO3 wash would probably be fine. What is the simplest route to removal of any remaining NBS in the workup?
Would an aqueous NaHSO3 wash be suitable for NBS removal?
-Cheers-vulture - 17-11-2013 at 07:10
NaHSO3 works, so does Na2S2O3. However, regardless of the reagent, you will be left with succinimide in
your product. This is why a NaOH wash is frequently used to draw it into the aqeous phase. If your product is soluble in hexane, you can precipitate
the succinimide. Be sure to remove any other solvent first. Asepsis - 17-11-2013 at 10:10
Thanks vulture.
The succinimide is rather soluble in aqueous, base or not. I think that should come out in any aqueous wash (and I'll likely have at least one dilute
NaHCO3 wash regardless). I was just concerned over the leftover NBS. As far as thiosulfate goes, I'd be wary of producing a big stinky mess of reduced
sulfur (found this out the hard way some time ago when reducing some Br2 w/ thiosulfate. But perhaps NBS reacts differently w/ thiosulfate than Br2.
Anyhow- I'm babbling meow. I'll move ahead with a couple NaHSO3 washes.
Thanks again!vulture - 17-11-2013 at 10:57
Quote:
I think that should come out in any aqueous wash (and I'll likely have at least one dilute NaHCO3 wash regardless).
You'd think that, but it happened to me multiple times that I had succinimide residue after an aqueous wash. Certainly if you are extracting from
dichloromethane or chloroform.
