Organic Chem- Stereoisomerism

Question 1

Definition of stereoisomers

Answer 1

Same structural formula but different arrangements of atoms in space

Question 2

Where can stereoisomers occur??

Answer 2

Only in alkenes because alkanes don’t have a fixed double bond, so it’s free to rotate

Question 3

Two types of stereoisomers??

Answer 3

Cis-trans and E-Z

Question 4

What are the requirements for E-Z isomerism??

Answer 4

Double bond between two carbon atoms

Different element/group attached to BOTH carbon atoms eg a H atom and CH3 group on both

Question 5

What’s an E isomer??

Answer 5

An E isomer means the same group on OPPOSITE sides of the double bond

Question 6

What’s a Z isomer??

Answer 6

Comes from zusammen which means together. The same group are on the same side of the double bond eg both hydrogen’s at the bottom

Question 7

What are the requirements for CIS trans isomerism??

Answer 7

C=C double bond
Two different groups attached to both carbons
ONE GROUP ON BOTH CARBONS MUST BE A HYDROGEN

Question 8

What are the cis and trans isomer??

Answer 8

The cis isomer has both H’s on the same side, whereas the trans isomer have the H’s on opposite sides

Question 9

How do you work out E and Z isomers when random groups are attached??

Answer 9

When random elements are attacked eg OH groups or CH2OH, you work out priority by looking at which element is attached to the C=C on each side first. If they’re both a carbon for example, you look at what the carbon is directly attached to. If one carbon was attached to 3 hydrogen’s but the other was attached to another carbon and two hydrogen’s, the second one has priority because the Mr of what it’s attached to is higher. If the two priority groups are on the same side, it’s the Z isomer, if not it’s the E isomer