Sciencemadness Discussion Board

Question about tartaric acid and it's use for resolution of racemic amines

FormicAcidAnimal - 24-11-2015 at 07:37

Hi there!
In this text (https://www.erowid.org/archive/rhodium/chemistry/amphetamine...) it says:
Quote:

....And in those methods, d-tartaric acid is used to obtain the dextro amine and l-tartaric acid to prepare the laevo amine. However while those processes are operable chemically, they have serious disadvantages, particularly with regard to the separation of l-amphetamine by means of d-tartaric acid, in that while d-tartaric acid is readily available and comparatively cheap, l-tartaric acid at the present time is both difficult to obtain and expensive in pure form (d tartaric acid comes from fruit, l-tartaric acid is 'unnatural')....


Though according to Wikipedia the usual E 334 tartaric acid used in foods actually is the L-form!?
I'm a bit confused - though I've been always a noob in stereochemistry ^^
Can someone explain it to me, please?

karlos³ - 24-11-2015 at 09:31

That is probably a mistake, as it is the other way around.
l-tartaric acid is the natural one, like it is in nearly every natural chemical with chirality. The d-form is mostly unnatural, that is also true for most amino acids.

Another chemical used to separate enantiomers is n-acetyl leucine.
Both isomers are readily available.

Nicodem - 24-11-2015 at 09:56

Quote: Originally posted by FormicAcidAnimal  
Though according to Wikipedia the usual E 334 tartaric acid used in foods actually is the L-form!?
I'm a bit confused - though I've been always a noob in stereochemistry ^^
Can someone explain it to me, please?

d-tartaric acid = L-tartaric acid = L-(+)-tartaric acid (is the natural stereoisomer)
l-tartaric acid = D-tartaric acid = D-(-)-tartaric acid

You don't need to know anything about stereochemistry. All it takes is about 15 seconds of googling.

Syntropymancer - 14-12-2015 at 17:57

Quote: Originally posted by Nicodem  
Quote: Originally posted by FormicAcidAnimal  
Though according to Wikipedia the usual E 334 tartaric acid used in foods actually is the L-form!?
I'm a bit confused - though I've been always a noob in stereochemistry ^^
Can someone explain it to me, please?

d-tartaric acid = L-tartaric acid = L-(+)-tartaric acid (is the natural stereoisomer)
l-tartaric acid = D-tartaric acid = D-(-)-tartaric acid

You don't need to know anything about stereochemistry. All it takes is about 15 seconds of googling.


Yeah, you can thank the confusing nomenclature that came out of the early understanding and work done on the chirality of molecules. (+) and (-), also d- and l- were to designate optical activity, that is, what direction they rotate in a polarized plane.

D- and L-, are unrelated to d- and l- or (+) and (-), as they are based on configuration to a reference molecule, glyceraldehyde, since most chiral molecules studied at the time were similar, amino acids.

R- and S- are used today, a system based on configuration system by substituent priority, so it does not require a reference molecule.

(also found using google)

chemrox - 14-1-2016 at 17:21

Did anyone else get lost here? I thought D- and d- were the same and related to R & S at least most of the time. Anyway if someone could expand a little on the D vs d nomenclature as relates to polaremitry I'd appreciate it.

byko3y - 14-1-2016 at 21:40

https://en.wikipedia.org/wiki/Chirality_(chemistry)
Different nomenclatures reflect different properties of a substance. An item can be cold and soft, although another item can be warm and soft.