5. Chirality

Which of the following has an asymmetric center?

CHBr₂Cl, BHFCl, CH₃CHCl₂, CHFBrCl, BeHCl

Of all the possible cyclooctanes that have one chloro substituent and one methyl substituent, which ones do not have any asymmetric centers?

Explain why compound A has two stereoisomers but compounds B and C exist as single compounds.

The following four structures are naturally occurring optically active compounds. Star (*) the asymmetric carbon atoms in these structures.

A molecule of the type shown here is discussed in greater detail in Section 6.5.1. Draw the mirror image. Is it superimposable? Switch the spatial orientation at both asymmetric centers. Have you generated a new molecule?

For each of the following molecules, identify all stereocenters and draw all possible stereoisomers.

(e)

Tetracycline is called a broad-spectrum antibiotic because it is active against a wide variety of bacteria. How many asymmetric centers does tetracycline have?

a. How many asymmetric centers does the following compound have?

b. How many stereocenters does it have?

The following compound has only one asymmetric center. Why then does it have four stereoisomers?

The stereoisomer of cholesterol found in nature is shown here.

a. How many asymmetric centers does cholesterol have?

b. What is the maximum number of stereoisomers that cholesterol can have?

How many stereogenic double bonds are in octa-1,3,5-triene? How many stereocenters are there? Draw and name the four stereoisomers of octa-1,3,5-triene.

Classify the following objects and molecules as chiral or achiral.

(h)

Identify the following molecules as chiral or achiral. If chiral, draw the nonsuperimposable mirror image and verify its nonsuperimposability.

(f)