[Puresimple]

Hi Everyone,

I am having a bit of trouble with some work I have to do for my organic chemistry lab. I have been trying to complete this for hours to no avail. I know my knowledge in organic chemistry is very weak, so I resorted to you guys to maybe guide me through to find the solution.

How would you resolve (±)-2-bromobutanoic acid using (-)-amphetamine? if the [α]_D=-33.4 then what would be the optical purity of the amine and %S and %R of the amine in the sample?

If anyone can provide at least a little bit of assistance I would be grateful...

[OrgXemProf]

I can't help wondering why an organic chemistry laboratory, presumably one that's associated with a college or university instructional course, would select a Class B controlled substance as a reagent to perform a routine resolution of a chiral alpha-halocarboxylic acid.

[Puresimple]

Well, the experiment didn't actually take place in the laboratory, it's just a worksheet that I have to complete in replacement for the actually lab. The actual experiment was  resolution of α-phenyethylamine with (+)- tartaric acid. Once we set the crystals to form until the following week, we were told that class there had been some contamination in the amine, which caused the improper crystals to form. So we just went over what was actually supposed to happen and was handed this worksheet to be complete instead. However, I can't seem to apply what I learned from that lab onto this worksheet. I did a lot of research online to try and figure this out, but I'm having a really hard time. so far I only have the structure of (±)-2-bromobutanoic acid and (-)-amphetamine written down.

would the solvent be the same as the resolution of α-phenyethylamine (methanol and NaOH) ? and if someone can direct me maybe where to find the known specific rotation of the pure sample, I think I can figure out the optical purity....

[sjb]

OK, what would you expect to happen if you reacted (±)-2-bromobutanoic acid and (-)-amphetamine?

[Puresimple]

i would expect diastereomers of the butanoic salts: (+)-RCOO-(-)-RNH₃+ and (-)-RCOO-(-)-RNH₃+  if I am correct? which i would then separate the diastereomeric salts and add a strong acid to retrieve the (+)-RCOOH and (-)-RCOOH....?

[sjb]

i would expect diastereomers of the butanoic salts: (+)-RCOO-(-)-RNH₃+ and (-)-RCOO-(-)-RNH₃+  if I am correct? which i would then separate the diastereomeric salts and add a strong acid to retrieve the (+)-RCOOH and (-)-RCOOH....?

Seems sensible