Isomerism

Question 1

what is the name of CH3-CH2-CH2-CH3

Answer 1

butane

Question 2

what is the name of CH3-CH-CH3
|
CH3

Answer 2

methylpropane

Question 3

what are the differences between butane and methylprropane

Answer 3

• their names are different

- due to their structural formulas being different

Question 4

what is the similarity between butane and methylpropane

Answer 4

• they both have the same molecular formula

- of C4H10

Question 5

what is the name given to the relationship between the two molecules

Answer 5

they are structural isomers of each other

Question 6

what does being a structural isomer basically mean

Answer 6

• they have different structural fromulae

- but have the same molecular formula

Question 7

what increases in this case as the number of carbon atoms increases

Answer 7

the number of different structural isomers you can have

Question 8

what are the two main types of isomerism

Answer 8

• chain isomerism

- position isomerism

Question 9

what does chain isomerism refer to

Answer 9

molecules with different carbon chains (chain lengths)

Question 10

what are an example of chain isomers and why

Answer 10

• butane and methylpropane
• because their carbon chains are different which give them different codes (but and prop)
• but they are still isomers

Question 11

what does position isomerism refer to

Answer 11

• molecules with the same functional group attached to different carbon atoms in the same carbon chain

Question 12

what is an example of position isomerism with propanol and why would they be considered to be position isomers

Answer 12

• propan-1-ol and propan-2-ol
• they have the same carbon chain and functional group
• but a different structural formulae due to the functional group being in a different position

Question 13

what is an example of two molecules in which chain and position isomerism is being shown (their names)

Answer 13

• 3-methylbutan-1-ol

- pentan-3-ol

Question 14

what is the structural formula of 3-methylbutan-1-ol

Answer 14

CH2-CH2-CH-CH3
| |
OH CH3

Question 15

what is the structural formula of pentan-3-ol

Answer 15

CH3-CH2-CH-CH2-CH3
|
OH

Question 16

what does stereoisomerism refer to

Answer 16

two different ways to arrange atoms or groups of atoms

Question 17

what is different about stereoisomers

Answer 17

• they have the same molecular and structural fromulae

- but have a different arrangement of atoms

Question 18

what is the structural formula of but-2-ene

Answer 18

CH3-CH=CH-CH3

Question 19

what is the first way you can arrange the atoms in but-2-ene

Answer 19

CH3 CH3
    |    |
   C=C      
    |    |
   H  H

Question 20

what is the second way you can arrange the atoms in but-2-ene

Answer 20

H CH3
    |    |
   C=C      
    |    |
CH3 H

Question 21

which isomer has the CH3 groups farthest away from each other and why

Answer 21

• the second isomer
• because they are across each other
• as one is on top and the other is on the bottom

Question 22

what abbreviation would you add to the beginning of that isomers name to indicate this

Answer 22

• trans

- which is latin for across

Question 23

what term would be used at the beginning of the first isomers name and why

Answer 23

• cis (latin for ‘on this side’)
• because the CH3 groups would be on the both above the double bond
• so they are only at opposite sides not at opposite ends of the molecule

Question 24

what is this type of stereoisomeric relationship called

Answer 24

• geometric isomers

- also known as cis-trans isomers

Question 25

why can stereoisomerism only exist in alkenes but not alkanes (specifically), what do alkenes have the alkanes dont)

Answer 25

because there needs to be s C=C bond for the cis and trans isomers to occur

Question 26

why does there need to be a C=C bond to stereoisomerism

Answer 26

- the presence of that bond leads to restricted rotation - meaning the groups attached to the C=C cant move around freely - alkanes dont have double bonds so the hydrogens can rotate freely

Question 27

``` is this a stereoisomer of but-2-ene and why H CH3 | | C=C | | H CH3 ```

Answer 27

- its not - because the CH3 groups are on the same side of the C=C double bond - which makes the carbon chain different as there is no chain of 4 carbon atoms

Question 28

what is that compound then, compared to but-2-ene and what is its name

Answer 28

- it is a structural isomer of but-2-ene | - and its name is methylpropene