Isomerism

Question 1

What is an isomer?

Answer 1

same molecular formula, different structural formula/arrangement of atoms

Question 2

What are 4 different types of isomerism?

Answer 2

-E-Z isomerism
-functional group isomerism
-chain isomerism
-positional isomerism

Question 3

What is a chain isomer?

Answer 3

same molecular formula, but their carbon atoms in their carbon skeleton are arranged differently

Question 4

What forms can chain isomers have?

Answer 4

-straight chain
-branched

Question 5

What is a positional isomer?

Answer 5

same molecular formula with the same functional group, but the functional group is on a different place in the carbon chain

Question 6

Explain the chemical differences/similarities in positional isomers

Answer 6

they have similar chemical properties as they have the same functional group

Question 7

What is a functional group isomer?

Answer 7

have the same molecular formula, but have different functional groups, so belong to different homologous groups

Question 8

Explain the similarities/differences in chemical properties in functional group isomers

Answer 8

they have different chemical properties as they have different functional groups

Question 9

What type of isomerism is E-Z isomerism?

Answer 9

stereoisomerism

Question 10

What are stereoisomers?

Answer 10

stereoisomers are molecules which have the same structural formula but their bonds are arranged differently in space

Question 11

What are the two types of stereoisomers?

Answer 11

-E-Z isomers
-optical isomers

Question 12

Why do some alkenes have E-Z isomers?

Answer 12

due to the presence of the C=C double bond that has restricted rotation, can’t freely rotate like normal C-C bonds, which fixes the rest of the molecule in a set position

Question 13

Why are alkenes highly reactive?

Answer 13

due to the presence of the C=C double bond, it is an area of high electron density so the double bond can then attack electrophiles

Question 14

Why is there restricted rotation about the C=C double bond?

Answer 14

the C=C bond cannot freely rotate due to the pi electron clouds above and below the plane of the sigma bond, so a large amount of energy is required to rotate it, hence it is known as having restricted rotation

Question 15

How do you know if something is the Z isomer?

Answer 15

when both groups are on the same side of the double bond (zusammen- together/ ON ZEE ZAME SIDE)

Question 16

How do you know if something is the E isomer?

Answer 16

when both groups are on opposite sides of the double bond (entgegen- opposite)

Question 17

When is it not possible to have E-Z isomers?

Answer 17

when there are 2 identical groups of atoms joined to the same carbon atom in a double bond

Question 18

How do you use CIP priority rules to figure out the E and Z isomers of an alkene?

Answer 18

1- number the carbon atoms
2- assign the atoms that are bonded to the C=C double bond on both sides either higher or lower priority (higher priority is higher atomic number)
3- if both higher priorities are on the same side then it is a Z isomer
4-if both higher priorities are on opposite sides then it is an E isomer

Question 19

Describe and explain the differences/similarities between E and Z isomers

Answer 19

geometric isomers have different physical and chemical properties
-Z-isomers have higher boiling points because they are more polar than E-isomers
-E-isomers have higher mElting points because they pack more closely together than Z-isomers