Chapter 5: Stereochemistry

Answers to Chapter 5 Practice Questions

5.1 Order the following groups based on decreasing priority for E/Z naming purpose.

A) -CH2CH2Br B) -CH2CH3 C) -CH(CH3)2 D) -C(CH3)3

Answer: D > C > A > B


  1. Draw the structure of the following compounds. Determine which one has an chirality center and label it with a star.


2. Label all the chirality centers in the following molecules.


5.3 Draw the pair of enantiomers of 2-chloro-1-propanol.


5.4 Determine the R/S configuration of the chirality center in following compounds.


5.5 Determine the relationship for each pair of molecules: enantiomers, identical, constitutional isomers, non-isomers:

5.6 Draw the diagram for Sample #5 by referring to the diagram for Sample #4.

80- 20 = 60 observed

5.7 Explain why, in step 3 of the above procedure, the answer should be reversed to get the final (actual) configuration?

According to the definition of a Fisher projection, the horizontal bond is the bond pointing towards the viewer. Therefore, when the lowest priority group is on a horizontal bond, it is on the position just opposite to the way defined by the Cahn-Ingold-Prelog rule, so the actual configuration should be the reversed version of whatever is initially obtained.

5.8 Indicate the configuration of the following compounds.


  • Draw all stereoisomers for 1-ethyl-3-methylcyclohexane.


  • Draw all stereoisomers for 1-ethyl-4-methylcyclohexane.


  • Draw all stereoisomers for 1,2-dimethylcyclohexane.



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