MNK - 24-9-2008 at 08:54
Towards the later stages of my alkaloid extractions I often find that the final solvent extraction (for whatever reason) often yields little in the
way of rewards. (Note; I am using Dichloromethane.) Anyway, my question is 'Can I discontinue my extractions after the basification step?' The
basification step (of the aqueous layer) which obviously precedes final solvent extraction always results in a cloudy basified h20 solution, which
seems to me to be packed with tons of yellowish "sumthings" which im assuming are precipitated alkaloids (Note: I am not referring to the 'white
particles' which appear and then disappear, which I know for a fact r alkaloids, I am referring to a dark yellow, almost orange colour to the
acidified h20)
'. Am I wrong? If one were so inclined, could this basified dark yellow h20 be evaporated and consumed as would have been done with the organic
solvent? or am I misn something entirely
chemrox - 24-9-2008 at 14:33
Suppose your alkaloid was soluble in DCM. You might extract the DCM solution with base to get rid of acidic impurities. Keep track of where your
compound is and don't discard anything until you know. If you pull it out of some plant with DCM, wash the acids out with base, you'll have it in DCM
along with a lot of other non-polar crap. Extract that with acid- now your alkaloid is in the aqeous layer which is minus most of the non-polar crap.
Now, treat your aqeous layer with base and extract it with DCM to get a more pure alkaloid which is now back in the DCM. Concentrate the DCM if
necessary and use an acid to crystallize the stuff out.
If you don't know the solubilities you might want to bubble HCl through the solvent solution to get the HCl salt. A lot of times this can be done
with con HCl in alcohol but I wouldn't count on it. Make HCl by adding H2SO4 to salt. (careful)
Ephoton - 24-9-2008 at 14:46
setup a continuous extractor. make sure it can work both liquid liquid extraction
and liquid solid extraction.
when doing an A/B slowly basify your acid extraction till ph is slightly basic.
then just put in continuous extractor using DCM.
to find out if your alkaloid is in solvent just turn off return tap for solvent
and alkaloid is left pure in the bottom collection flask.
using sep funnels for this kind of stuff is a real waist and in an unexperianced
persons hands (often including my self) can lead to loss in yields.
becarefull stripping water off of a freebase. a lot of freebases will steam distill.
best if you want to strip the water off a freebase to use xylene and ethanol to
azeotropicaly distill the water off.
this way you upset the azeotrop of your freebase and maby keep more of it
in the distillation flask.
maby being the key word there.
Nicodem - 29-9-2008 at 00:26
Please post vague or unanswerable questions to Beginnings section!
(I'm moving this thread there)