Isomerism

Question 1

isomer definition

Answer 1

2 molecules that have the same molecular formula but differ in the way their atoms are arranged

Question 2

what are the difference between isomers?

Answer 2

have different physical properties and sometimes different chemical properties

Question 2

structural isomerism definition

Answer 2

-same molecular formula
- different structural formula

Question 3

stereoisomerism definition

Answer 3

• same molecular formula
• same structural formula
• different spatial arrangements (geometries)

Question 4

what are the three types of structural isomerism?

Answer 4

• chain
• position
• functional group

Question 5

what are chain isomers?

Answer 5

type of structural isomerism.
carbon chains arranged differently - different carbon skeletons.

Question 6

what are position isomers?

Answer 6

type of structural isomerism.
the functional group is attached to the main chain in a different location.

Question 7

what are functional group isomers?

Answer 7

type of structural isomerism.
the atoms are reorganised to give a different functional group.

Question 8

between what 4 pairs is functional group isomerism shown?

Answer 8

• alkenes and cycloalkanes
• aldehydes and ketones
• alcohols and ethers
• carboxylic acids and esters

Question 9

what is the functional group for aldehydes?

Answer 9

Question 10

what is the functional group for ketones?

Answer 10

Question 11

what is the functional group for alcohols?

Answer 11

C—OH

Question 12

what is the functional group for ethers?

Answer 12

C - O - C

Question 13

what is the functional group for carboxylic acids?

Answer 13

Question 14

what is the functional group for esters?

Answer 14

Question 15

what is E/Z isomerism?

Answer 15

type of stereoisomerism that occurs due to the restricted rotation around the carbon double bond

Question 16

_____ show E/Z Isomerism

Answer 16

alkenes

Question 17

Explain how alkenes show E/Z isomerism

Answer 17

1. Alkenes have restricted rotation around their C=C double bonds
2. & if both of the double-bond carbons have 2 different functional groups attached to them = get 2 stereoisomers (E/Z isomerism)

Question 18

why can’t alkanes and halogenoalkanes display E/Z isomerism?

Answer 18

free rotation around the single carbon bond- means that the molecule are still the same, just rotated

Question 19

Where are the same groups situated in (cis) Z-isomer?

Answer 19

Either both above or both below double bond

(matching groups are on ‘ze zame zide’)

Question 20

Where are the same groups situated in (trans) E-isomer?

Answer 20

Same groups positioned across the double bond

Question 21

What rules do we use to identify whether a molcule with a C=C bond, surrounded by 3 or 4 different functional groups, is a E- or Z- isomer?

Answer 21

Use the Cahn-Ingold-Prelog (CIP) priority rules

Question 22

Describe how we use the CIP rules to identify a E-/Z-isomer

Answer 22

Identify the groups directly bonded to each of the C=C carbon atoms
Assign a priority by finding the atom with the highest atomic number - this given the highest priority
If higher priority groups = same side of molecule = Z-isomer OR if higher priority groups = different sides of molecule = E-isomer

Question 23

CIP rules: What do you do if the atoms directly bonded to carbon are the same?

Answer 23

Look at next heaviest atom in the groups to work out which has the higher priority

Question 24

what is the polarity of an E-isomer?

Answer 24

polar bonds cancel each other out

Question 25

what is the polarity of a Z-isomer?

Answer 25

more polar than E-isomers