Midterm 2

Organic Chemistry 1

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Question 1

Circle the chiral centers in the following molecule:

Solution

Question 2

Assign R and S configuration to the chirality centers of the following molecules:

Solution

Question 3

Derivative A has an [

α

]_D = + 59°.

Draw the structure of the derivative with an [ $α$ ]_D = - 59°.

Draw the structure of the derivative, which is stereoisomer of A and has an [ $α$ ]_D = 0°.

Solution

[ $α$ ]_D = 0° ⇒ meso compound ⇒ molecule with a plane of symmetry:

Question 4

Use heavy wedge and dash lines to show the R, R configuration of compound B.

Draw the structure of compound C.

Is C a chiral or achiral compound? Justify.

Solution

Question 5

Complete the following reactions and show stereochemistry.

Solution

Question 6

Draw the skeletal structures of trans and cis 1-bromo-2-iodocyclohexane.

Draw the 2 chair conformations of each isomerand circle the most stable conformer, knowing that I is much larger than Br.

What is the more stable isomer?

Solution

The more stable isomer is the trans isomer because one of its conformations has the two substituents in the equatorial position.

Question 7

What is the relationship between G, H and I?

Which isomer is the more stable?

Solution

G and H are enantiomers.

G and I are diastereomers.

H and I are diastereomers.

The more stable isomer is I because one of its conformations has the two substituents in the equatorial position.

Question 8

Draw the structures of the 2 compounds obtained by mono-bromination of J.

Solution