Recrystallizing Pseudoephedrine HCl (by Geezmeister)

tina_craig · Wed Feb 09, 2005 10:50 pm

Put the pseudo in a beaker, cover with 3 to 4 times its depth of dried acetone, bring to a gentle boil, and drip in MeOH a few drops at a time with stirring. When the addition of another drop or two doesn't reduce the amount of solids (and almost all the solids will be gone by now) proceed with only one drop of alcohol at a time, stir, give it a few seconds, do another. When no reduction in the solids takes place with the addition of the alcohol, dump the contents of the beaker through a funnel with a soft (rather than tight) charmin plug, prewetted with MeOH. By this I mean a corner folded up and pressed in the funnel neck. Use a small funnel, with a small neck. You don't want to lose much to the paper, so just a corner is used.) Chill the filtrate and let crystals form.

Filter out the crystals, rinse with acetone, add the acetone to the mother liquor remaining from the first crystallization. Place on low heat and reduce to alcohol alone, and reduce the alcohol to saturation. When the first signs of crystals start forming on the surface of the alky solution, add as much acetone (or more) than you have alcohol. Chill, collect the crystals and solids that form, combine with the other crystals, and if you like, reduce the liquor again to see if you get any more crystals.

Take the crystals you got from the motherliquor and do the whole process again.

Admitted this presumes you have pretty good clean pseudo to start with, because if you don't it won't help you much, you will lose to much yield.

An alternative is to mix 100 ml of xylene with 100 ml of naptha. add about another 10 ml of each for each gram of pseudo you have you want to clean. You need enough solvent to hold gakks easily, but don't need quarts for a few grams. I usually use a minimium of 200 ml to have enough to work with, then scale up according to size. 400-500 ml of xylene/naptha works fine for 10-12 grams of pseudo... it isn't that volume dependent, as long as you have enough to hold the gakk and keep the pseudo from settling to the bottom and sticking.

Dissolve the pseudo in MeOH sufficient to dissolve it all, then drip into the xylene/naptha mix and then heat on medium high heat to 105C. At 70-C the pseudo will being to precipitate, and at 90 you will have all the alky boiled off and the pseudo should be white stuff mixed in the solvents. Keep heating to 105C and filter through a single coffee filter at that temp. Rinse immediately with MEK. Dry under a lamp.

Let the solvent cool. The shit that is in will convince you the first time you do this that you didn't have clean pseudo. If you get color changes in the solvent to violet or to beer color... you dumped most of the orange II in the mix into the solvent, where it remained at heat when you filtered the pseudo out.

Then do a recrystallization, one time, of what you have here.

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Crystallization: the most important purification method, especially for small-scale experiments.

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tk3god · Tue Feb 22, 2005 9:18 am

So, just for clarification, KOH 1st then rxtl as above should yield near pristine pse? Just got a chem book, too, so gonna be dangerous soon Smile

. And, rxtl w/out clean pse will cost more pse than bee worthwile? So one couldn't rxtl pse that's "so-so" clean just to clean it up, needs to start somewhat clean, yes?