Stereoisomerism

Question 1

What are stereoisomers?

Answer 1

Molecules with the same structural formula but a different arrangement of the atoms in space

Question 2

What are the two types of stereoisomerism?

Answer 2

E/Z isomerism and optical isomerism

Question 3

Where does E/Z isomerism occur?

Answer 3

In compounds with a C=C double bond

Question 4

Where does optical isomerism occur?

Answer 4

In a wide range of compounds, including alkanes with no functional groups

Question 5

Why is there stereoisomerism around double bonds?

Answer 5

Rotation about the double bond is restricted and the groups attached to each carbon atom are therefore fixed relative to each other

Question 6

Why is there rigidity around the double bond?

Answer 6

Due to the position of the pi bond’s density above and below the plane of the sigma bond

Question 7

What are the two conditions for E/Z isomerism to occur?

Answer 7

1) A C=C double bond
2) Different groups attached to each carbon atom of the double bond

Question 8

What is cis-trans isomerism?

Answer 8

A special case of E/Z isomerism

Question 9

What is the condition for cis-trans isomerism to occur?

Answer 9

One of the attached groups on each carbon atom of the double bond must be the same

Question 10

What is a cis isomer?

Answer 10

An isomer with the same bonds on the same side of the molecule

Question 11

What is a trans isomer?

Answer 11

An isomer with the same bonds diagonally opposite each other

Question 12

What type of isomer is cis?

Answer 12

Z isomer

Question 13

What type of isomer is trans?

Answer 13

E isomer

Question 14

What is Cahn-Ingold-Prelog nomenclature used for?

Answer 14

Isomeric compounds containing C=C bonds that can’t be classified as either cis or trans

Question 15

What is Cahn-Ingold-Prelog nomenclature?

Answer 15

A naming system where each carbon atom in a double bond are given a priority based on their atomic number

Question 16

What are the two rules of Cahn-Ingold-Prelog nomenclature?

Answer 16

1) If groups of higher priority are on the same side, the compound is a Z isomer
2) If groups of higher priority are diagonally placed across the double bond, the compound is an E isomer

Question 17

What is the relationship between atomic number and priority?

Answer 17

The higher the atomic number, the higher the priority

Question 18

What happens if two atoms attached to one carbon atom in a double bond are the same?

Answer 18

You will need to continue down the branches to find the first point of difference, and the group with the higher atomic number at the first point of difference has the higher priority