Dextro vs. Levo Amphetamine - how to seperate them

[bobsagat]

Does anyone know how to seperate the different enantiomers of amphetamine after synthesis?

no synthesis questions - nuke

 

[PsychedelicDoctor]

no synths, sorry.

also, separating isomers requires some very expensive equipment.

 

[skillet]

So you want to resolve the amphetamine you extracted from Adderall? Recrystallisation with D-tartaric acid (the natural form). 1:1 amp base to tartaric acid preferentially crystallises the D-amp salt, you really need a polarimeter to check it's working though. You could maybe knock one up with a pair of polaroid glasses, a plastic/glass tube (with a square or rectangular cross-section - path length factors into the equation so you can't just use a test tube) and a protractor or smartphone spirit level that measures angle. Or something like this.

alpha-D of a 80mg/mL water solution of the D-amp D-bitartrate salt is apparently +30.8 degrees. Link

 

[iconoclast56]

In the lab, one would separate enantiomers by converting them into diastereomers then separating the diastereomers. Enantiomers have identical physical properties (such as solubility, melting point etc.) whereas diastereomers have different physical properties and can thus be separated using physical methods.

 

[bobsagat]

Okay Skillet, you sound like you know what you're talking about. I don't want to wait till the end of the synth to seperate the dextro-rotatory from the levo-rotatory enantiomer because I use a *censored* for a nucleophilic substitution in one step of my synth and would prefer to use as little *censored* as possible, because it's the most expensive compound in my synth. If I did what you are suggesting, I'd effectively be throwing out half of my *censored*. Ouch. Allow me to restate the problem - I want to separate L-*censored* from D-*censored*. I know to use a pure enantiomer of tartaric acid, that it will attach to the amine group, and then I have L-D and D-D diastereomers which presumably have different properties. How do I seperate these? You're suggesting that I could do it by fractional crystallization, but how do I know that the L-D diastereomer will be less soluble then the D-D diastereomer?

Thanks for the help.

 

[skillet]

No synth talk, edit your post or this thread's going to be locked.

It's in the link - with a 1:1 molar ratio of acid to amine the D-D salt crystallises preferentially.

 

[atrollappears]

How to make the dextrorotary compound? Start with the dextrorotary reagent
Come on... it's the first damn google result.

 

[nuke]

with the magic of tartaric acid

there are a number of patents if i recall correctly, look them up.