DF 9 - Isomerism Flashcards
Define “isomers”
Molecules with the same molecular formula but with different arrangement of the atoms
What are the two types of isomerism?
- Structural isomerism
- Stereoisomerism
Define “structural isomers”
Molecules with the same molecular formula but with the atoms bonded together in a different order
Name the 3 types of structural isomer
- Chain isomerism
- Position isomerism
- Functional group isomerism
What is chain isomerism?
Molecules with the same molecular formula having different arrangements of the carbon skeleton
What are the two ways carbon skeletons can be arranged?
- As a straight chain
- As branched chains
Are the chemical properties of chain isomers similar or different?
Similar
Are the physical properties of chain isomers similar or different?
Different
Give one physical property of chain isomers that differ and why.
Boiling point differs because of the changes in the shape of the molecule
The more ____ in an alkane, the more chain isomers it has.
Carbon atoms
Which alkanes have no chain isomers?
- CH4
- C2H6
- C3H8
What is position isomerism?
Molecules with the same molecular formula having their functional group situated in different positions on the carbon chain
Are the physical properties of position isomers similar or different?
Different
Are the chemical properties of position isomers similar or different?
Different
What is functional group isomerism?
Molecules having the same molecular formula but different functional group
Are the physical properties of position isomers similar or different?
Different
Are the chemical properties of position isomers similar or different and why?
Different as they belong to different homologous series
What are the two types of stereoisomer?
- E/Z isomerism
- Optical isomerism
Explain how E/Z isomers form in alkenes due to restricted rotation
- Alkanes don’t contain any double bonds, single bonds allow atoms to rotate freely so they cannot form isomers of each other
- Alkenes have at least one double bond, double bonds are rigid and don’t allow the atoms to rotate
- Alkenes still contain single bonds in their molecules which means atoms can rotate these
When is an alkene an E isomer?
When the hydrogens are across the double bond
When is an alkene a Z isomer?
When the hydrogens are on the same side of the double bond
When do we use the terms “E or Z isomer”?
Only when the two groups that are the same are hydrogens
What is an E isomer also known as?
Trans isomer
What is an Z isomer also known as?
Cis isomer
What is optical isomerism?
When two compounds are non superimposable mirror images of each other
When does optical isomerism usually happen?
A central carbon atom with four groups arranged around it
What property of alkenes allows E/Z isomers to form?
Restricted rotation around the C-C double bonds
