RP/I2 post-reaction workup: The short version-Osmium

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Osmium
(Stoni's sexual toy)
04-23-03 09:52
No 428962

RP/I2 post-reaction workup: The short version
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*almost speechless*

Almost, but not totally.

Once you're done with the reflux let it cool down a little (or don't, doesn't really matter). Colour doesn't matter either, mine was always almost black due to I2. Dilute with several volumes of water, because pouring conc. HI through filter paper is a pretty dumb idea, and concentrated solutions aren't easily extracted. Just fill up that flask with water, suction filter out the rP, rinse flask once or twice more with water and pour it through the same filter too. Use proper lab grade filter paper and you will catch all rP during the first time.
The dilution with all that water will cause the non-acid soluble side products to come out of solution. The shit turns yellowish/reddish and milky. You cannot look through it easily anymore.
To remove the unwanted shit rinse the flask with some NP solvent (toluene and xylene being prefered). Pour through the same filter still holding the rP. Shake the shit out of the NP/water layer, because half-assed stirring isn't good enough. Let phases separate, discard NP layer. Repeat NP wash twice. Most of the colour and pretty much all of the side-products will be gone by now.
Evap the NP washes if you like, so you can look at that nasty gunk this simple step removes.
Wash the rP with a little acetone or MeOH, let it dry and reuse it.

Basify the strongly acidic water layer with NaOH solution. Concentration doesn't matter, 20% should be ok. pH doesn't matter either as long as it's strongly basic. Nothing wrong with pH14 at this point. The solution will heat up considerably, and the ---- freebase can be seen. Extract it a few times with tolly. Shake hard. Take your time, let layers separate completely. The water layer might start to solidify into a slush while it cools down. Do not freak out. There's a whole lot of sodium phosphate and sodium iodide in there. Simply add some hot water to redissolve everything, and proceed.

Then gas the tolly solution. If you were careful when separating the layers you don't even need to dry the tolly prior to gassing.
Filter out the product, barely cover the product with acetone, suck dry (just add the acetone to the tolly containing your freebase), repeat gassing until nothing comes out anymore. I've had reactions where I had to interrupt the gassing 8 or 9 times to filter out the product.

Optional, often not needed: dissolve already bright white ---- dust produced that way in a little hot anhydrous IPA. Add several volumes of acetone. Place in freezer overnight. Filter out product. Solvents from gassing and this recrystallisation are combined, evaporated (*), and the residue is again dissolved in a little hot IPA. Gas the IPA with HCl to make sure all ---- is neutralized, add excess of acetone, into freezer for a few hours, filter out additional crop of product. Evap solvents just for shit and giggles, and tweak around with it for an afternoon or two, maybe you will get another line of mmmmeth out of it. Or just dump that shit. Or save it to be worked up some future time.

(*)If you have a rotovap you can easily separate the solvents at this stage and reuse them. The tolly for example can be used to wash the still acidic post reaction mixture. IPA/acetone is used to rinse flasks and glassware. A rotovap will speed all this up considerably, and you can e.g isolate the ---- freebase before crystallisation by removing all sovents under vacuum.

FINALLY:

The short version:
dilute with plenty of water, filter rP out, extract the crap with NP (3 times, discard), basify the water layer, extract freebase into tolly (3,4 times is ok), gas it. Recrystallise product. Done.

Look! Two lines, and all is said!

You drama kings make this shit way too complicated.
Never judge a reaction by its looks, colour or whatever. You won't know until you're finished, and all this drama will only wreck your nerves.

I'm not fat just horizontally disproportionate.
http://www.whatreallyhappened.com