EXPT 6 resolution revised 101211

EXPT 6 resolution revised 101211 - EXPT. 6: Resolution of a...

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EXPT. 6: Resolution of a Racemic Mixture of Phenylsuccinic acid As discussed in the polarimetry section of the techniques, enantiomers of a given compound have the same formula, but differ in the spatial arrangement of the atoms. The (+) isomer of a set of enantiomers is the non-superimposable mirror image of the (-) isomer. The two enantiomers have the same chemical and physical properties, but the (+) isomer rotates plane-polarized light to the right and the (-) isomer rotates plane-polarized light to the left. All of the other properties are exactly the same, only the “optical rotation” is different. Because the chemical and physical properties are the same, the two enantiomers are very difficult to separate. Louis Pasteur was able to separate a salt form of racemic tartaric acid into (+)-tartaric acid and (-)-tartaric acid with tweezers, but most enantiomers need to be separated by forming diastereomers of the compound. Diastereomers are stereoisomers, but they are not mirror images of each other. They normally have different physical properties, and sometimes different chemical properties. We will take advantage of a physical property (solubility) in this experiment in order to separate two diastereomers of phenylsuccinic acid. The (+) isomer and the (-) isomer of phenylsuccinic acid have the same physical and chemical properties. However, if the acid is combined with an optically active base, such as (-)-proline, the diastereomers which form have different solubilities in isopropyl alcohol. The diastereomeric salt formed between the (+)-phenylsuccinic acid and (-)-proline is much
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This note was uploaded on 03/06/2012 for the course CHEM 301 taught by Professor Sahli during the Spring '07 term at VCU.

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EXPT 6 resolution revised 101211 - EXPT. 6: Resolution of a...

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