Experiment 2


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1 CH241 EXPERIMENT #2 CHEMICAL RESOLUTION OF RACEMIC IBUPROFEN WITH A CHIRAL AMINE 1 Introduction: Ibuprofen ( 1 ) is a chiral carboxylic acid that belongs to a class of pharmaceuticals known as non-steroidal anti-inflammatory drugs (NSAIDs). It is present in over-the-counter medicines such as Motrin and Advil among others. The ( S ) form of ibuprofen is pharmacologically active, although the inactive ( R ) form is slowly converted into the ( S ) enantiomer in the body. Ibuprofen is generally sold in its racemic form but it appears that formulations containing just the ( S ) isomer is more effective, and thus there have been efforts to prepare exclusively the active enantiomer. 1 As you learned in class and in chapter six, enantiomers can be distinguished by other chiral compounds. You will use that idea to resolve a racemic mixture of ibuprofen using the chiral base ( S )-(-)- α -phenylethylamine ( 2 ) as the resolving agent, through the formation of diastereomeric salts. One of these diastereomeric salts is soluble in water but the other is not. Separation of the two salts can be accomplished using this solubility difference, allowing you to recover enantiomerically pure ( S )-ibuprofen and determine its optical rotation and purity. H 3 C O OH CH 3 CH 3 1 H 3 C NH 2 H 2 Week 1: Resolution and Isolation of ( S )-Ibuprofen Procedure Step 1 : In a 100 mL round-bottomed flask equipped with a thermometer, combine 3.0 g of racemic ibuprofen with 30 mL of aqueous 0.24
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This note was uploaded on 10/06/2010 for the course ES ES271 taught by Professor Machaut during the Spring '10 term at Colby.

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