beerwiz
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How to decompose precipitated alkaloids in Wagner's Reagent?
Wagner's reagent is an alkaloid precipitant and constists of 2g Iodine and 6g Potassium iodide in 100ml water.
So I precipitated some alkaloids using this reagent. Does anybody know how to decompose the iodide to get the free alkaloids?
If picric acid was used to precipitate the alkaloids (1g picric acid in 100ml water), then simple ammonia or NaOH frees them up. But what about
alkaloids precipitated with Wagner's Reagent?
[Edited on 13-11-2015 by beerwiz]
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careysub
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Quote: Originally posted by beerwiz  | Wagner's reagent is an alkaloid precipitant and constists of 2g Iodine and 6g Potassium iodide in 100ml water.
So I precipitated some alkaloids using this reagent. Does anybody know how to decompose the iodide to get the free alkaloids?
If picric acid was used to precipitate the alkaloids (1g picric acid in 100ml water), then simple ammonia or NaOH frees them up. But what about
alkaloids precipitated with Wagner's Reagent?
[Edited on 13-11-2015 by beerwiz] |
From an olde book:
"The alkaloids may be recovered from their polyiodides by treating the precipitate with sulphurous acid, a sulphite and dilute sulfuric acid, or
sodium thiosulphate and then adding an alkali and shaking with a suitable immiscible solvent. Treatment with sodium thiosulphate ("hyposulphite"),
avoiding excess, is a convenient means of purifying the polyiodides of coprecipitated foreign matter. The reduced solution is filtered and again
treated with Wagner's reagent, when the polyiodid is obtained in a condition of purity. "
https://books.google.com/books?id=p77nAAAAMAAJ&pg=PA138&...
[Edited on 13-11-2015 by careysub]
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AvBaeyer
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Perhaps simple reduction of the iodine with sodium thiosulfate might work. That's what I would try.
AvB
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AvBaeyer
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Wow- simultaneous post with Careysub! At least we gave the same answer.
AvB
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Syntropymancer
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sodium metabisulphite works too, we use it regularly to clean up I2.
[Edited on 15-12-2015 by Syntropymancer]
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beerwiz
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Thanks to all who responded on this thread, very useful info.
Does anyone know if when Wagner's reagent is added to a neutral or acidic aqueous solution and there's zinc acetate in the solution, will the zinc
precipitate along with the alkaloids? Or will the zinc acetate remain in solution?
[Edited on 23-12-2015 by beerwiz]
[Edited on 23-12-2015 by beerwiz]
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beerwiz
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Tested it, the zinc acetate remains in solution and does not precipitate.
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