Chem2O6 - 1997/98

Problem Set #6 October 24, 1997

1. Draw and name all the stereoisomers that are possible for each of the following compounds. Identify the enantiomers and diastereomers.

Structures PS6 #1

2. Draw perspective formulas for all the stereoisomers of the following compound. Identify which ones are optically active and which are meso forms. For the optically active ones, identify enantiomers and diastereomers.

Structure PS6 #2

3. The carboxylic acid shown below was synthesized as a racemic mixture. When pure (R)-1-amino-1-phenylethane was added to an ethanol solution of the acid, two compounds were formed. One of these crystallized out of solution immediately and could be filtered off, while the other was isolated by distilling the ethanol from the mother liquors.

2-methyl-2-phenyl-3-butenoic acid

(a) Draw perspective formulas of the two compounds and identify their relationship to one another.

(b) The two compounds were each dissolved separately in water, the solutions were made basic with 1 M aqueous sodium hydroxide in separatory funnels, and then extracted with ether. For each one, identify which compound would be present in the aqueous layer and in the ether layer.

(c) What would you do to isolate the compounds present in the aqueous layers?

(d) Explain what would happen if racemic 1-amino-1-phenylethane was used in the above procedure. Trace through each of the steps above, and draw perspective formulas of all compounds present at each stage.

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24oct97; wjl