5. Chirality

Do the following structures represent identical compounds or a pair of enantiomers?

When pure (S)-lactic acid is esterified by racemic butan-2-ol, the product is 2-butyl lactate, with the following structure:

(a) Draw three-dimensional structures of the two stereoisomers formed, specifying the configuration at each asymmetric carbon atom. (Using your models may be helpful.)

(b) Determine the relationship between the two stereoisomers you have drawn

What type of isomerism is indicated by each of the following pairs of molecules? Be as specific as possible.

(a)

Identify

1. constitutional isomers

2. stereoisomers

3. cis–trans isomers

4. chiral compounds

Draw the mirror image of the following molecule. Then, using the mirror image generated, switch the spatial orientation at the asymmetric center. Is the final structure the enantiomer of the original? If not, what is it?

For each pair, give the relationship between the two compounds. Making models will be helpful.

(h)

Make a model and draw a three-dimensional structure for each compound. Then draw the mirror image of your original structure and determine whether the mirror image is the same compound. Label each structure as being chiral or achiral, and label pairs of enantiomers.

(e)

(f)

For the molecules shown,

(i) count the number of stereocenters present and

(ii) draw all possible stereoisomers.

(iii) Identify the relationships between stereoisomers as enantiomers or diastereomers.

(a)

(i) Which of the following pairs of compounds would you expect to have different physical properties?

(ii) What is the relationship between each of the pairs?

(iii) Assign the absolute configuration of each stereocenter to confirm your answer.

(a)

Draw the structure for a compound with molecular formula C₂H₂I₂F₂

a. that is optically inactive because it does not have an asymmetric center.

b. that is optically inactive because it is a meso compound.

For the molecules shown,

(i) count the number of stereocenters present and

(ii) draw all possible stereoisomers.

(iii) Identify the relationships between stereoisomers as enantiomers or diastereomers.

(b)