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(S)-(−)-α-Methylbenzylamine extraction from racemic mixture

William Dampier

Well-known member
Jul 19, 2021
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Reaction scheme:

This compound need for dextroamphetamine synthesis.

1. 124 g (S, S)-tartaric acid in 1800 ml methanol is placed in a flask.
2. Heated to boiling.
3. Slowly dropwise 100 g of racemic α-methylbenzylamine base.
4. Stop warming and left at room temperature for 24 hours.
5. Separated the dropped crystals on filter, and washing with methanol. Crop 75 g.
6. The combined methanol was evaporated to 700 ml amount.
7. The mixture left for 24 hours at room temperature.
8. Separated the dropped crystals on filter, and washing with methanol. Crop 12 g.
9. All separated crystals were combined and dissolved in hot 2000 ml methanol and concentrated to 1400 ml.
10. Repeat steps 4,5,6,7,8 and dry crystals (61 g), concentrated to 300 ml and after 24 hours filtered and dry 13 g crystals.
11. The total yield of the pure (−)-amine salt is 74 g.
Last edited by a moderator:
Mar 23, 2022
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I read the original patent. there they wrote that per 2mol of amphetamine they add 1mol of tartaric acid and dissolve it in the right amount of alcohol. heat to a boil and set aside to crystallize. they separate the aqueous phase from the crystals and carry out another recrystallization. they repeat this operation several times. then alkali is added to the combined water phases to raise the pH to 11. two phases are formed. one is oil. I understood the original patent well. will the actions carried out in this way give the appropriate effect?https://patents.google.com/patent/US2276508A/en
Two mols, for example, 2'70 grams, of racemic e-methylphenethylamine base are reacted with one mol (1'50 grams) of d-tartaric acid, thereby forming d1-a-methylphenethylamine d-tartrate. a neutral salt. The neutral salt thus obtained is fully dissolved by the addition of sufficient, say about one liter, of absolute ethanol, and heating to about the boiling point. The solution is then allowed towel to room temperature with occasional stirring to eiiect crystallization. The crystals are filtered oil and will be found to contain a preponderance of the laevo enantiomorph. On recrystallization the preponderance of the lenantiomorph is increased and the process is repeated until no further change in optical rotation is effected and a reading of is obtained in a concentration of 8 grams per 100 cc. of aqueous solution. The product thus obtained is Liz-methylphenethylamine d-tartrate. The residual solid in the mother liquors is repeatedly and systematically crystallized, yielding a further fraction of biz-methylphenethylamine d-tartrate which may be purified by recrystallization. d-a-methylphenethylamine may be readily recovered from the mother liquors by the addition of tartaric acid thereto for the formation of acid tartrates and separation of d-a-methylphenethylamine d-bitartrate by crystallization.
The free base'of either optical isomer may be obtained by addition to the d-tartrate in the case of the laevo isomer and the d-bitartrate in the case of the dextro isomer of alkali in excess, as, for example, by the addition of an aqueous solution of caustic soda, which will cause the base to separate as an oil which may be recovered and purified by any well known procedure.