03-19-04 00:28
No 496095
or the acid it picked up?
example
DXM HBr is only slightly soluable in H2O
would DXM HCL have the same characteristics, or because it is a HCL salt be more soluable?
Thanks for answering my newbie question.
(Chief Bee)
03-19-04 01:33
No 496105
Solubilities cannot be predicted that easily. It is a function of the properties of both the amine and the acid together, and thus only some general trends can be outlined, such as amine hydrochlorides are most often water soluble (but not always).
Some factors influencing solubilities can be seen here: Post 357689 (Osmium: "Solubility of compounds", Chemistry Discourse)
The Hive - Clandestine Chemists Without Borders
(Stranger)
03-19-04 02:07
No 496107
thanks, Im just racking my brain on ways that it might be able to seperate DXM and Pseudo, I was hoping this would be one of them.
(Newbee)
03-22-04 01:58
No 496600
the different alkaloids cross from polar to nonpolar at a particular pH, and about 1 pH measure either side of this has to be used to ensure 98% or better exclusion or inclusion of the alkaloid across the extraction. (roughly speaking... it varies a bit but 1 pH point is about how far the curve takes to get to the other side, soluble or insoluble)
ephedrine's pKa is 9.6 so that would be the same as pseudoephedrine
DXM's pKa is 9.2... so that's not quite big enough a difference, although done repeatedly it would have an effect, if 20% pseudo comes across, then do it three times and that's 20% of 20% of 20% coming across, ie 1/125... and left in the base solution will be 20% of the pseudo each time, which you will basify further and extract out... or something. anyway, they are separable by pH but only if you have accurate pH measurement and there would be probably a minimum extra 5-10% loss from having to fiddle with it so much.
if someone ever invents a method of column chromatography that isn't so damn fiddly you'd be able to use that pH and make one compound slide further down than the other and voila...
i might be remembering wrongly, but meth steam distills whereas ephedrine doesn't. does dxm steam distill? (or vice versa - the other way around sounds more hopeful)
(Chief Bee)
03-22-04 07:08
No 496625
ephedrine's pKa is 9.6 so that would be the same as pseudoephedrine
That is an incorrect conclusion.
if someone ever invents a method of column chromatography that isn't so damn fiddly you'd be able to use that pH and make one compound slide further down than the other and voila...
The nice thing about column chromatography is that you don't have to fiddle with pH for it to work, It can separate different compounds anyway.
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