OCHEM Question Help

[quand]

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hi, can anybody help me by explaining this question? Thanks

What is the stereochemical relationship between the salts formed by (+)-tartaric acid with racemic 1-phenylethanamine. The answer is diastereomers but I can't seem to figure out why.

 

[Demps]

Wording is kinda confusing but

I'm thinking (+), (-) relationship here with multiple chiral centers lead to suspect the relationship as diastereomers

Similar to how L-glucose (-) and D-glucose (+) are examples of epimers. Their orientations are exactly the same except the 5th carbon that decides the L and D orientation. Epimers are examples of diastereomers. I believe + - tartaric acids should be epimers as well, so diastereomers with respect to one another

 

[Gury410]

hi, can anybody help me by explaining this question? Thanks

What is the stereochemical relationship between the salts formed by (+)-tartaric acid with racemic 1-phenylethanamine. The answer is diastereomers but I can't seem to figure out why.

Tartaric acid is a resolving agent used in separating racemic mixtures (mixture of R and S) into their pure compounds (pure R and pure S). Since enantiomers have very similar properties, it is difficult to separate them based on things like boiling point, melting point, weight, etc. The tartaric acid reacts with both enantiomers of phenylethylamine and forms two different salts, each now with 2 chiral centers (instead of originally one) and forms a temporary diastereomer. These 2 new salts of PEA now have different physical properties and can be separated by distillation/crystallization/whatever. Once the 2 salts are separated, the tartarate can be removed from each solution and you now have two solutions of separated enantiomers of the original PEA mixture.