DF.9 Flashcards
Shapes of molecules, structures, and E/Z isomerism
What are two different ways atoms can be arranged in isomers and what they referred to as?
- When atoms are bonded together in a different order in each isomer. This is known as structural isomerism.
- When the order of bonding is the same, but atom have different arrangements is space in each isomer. This is known as stereoisomerism.
What formula is different for structural isomers?
Their structural formulae.
What are the three types of structural isomerism?
- Chain isomerism
- Position isomerism
- Functional group isomerism
What is chain isomerism?
Isomers have the same molecular formula, but different arrangements of carbon atoms are possible creating breaches etc. For example, CH3CH2CH2CH3 and CH3CH(CH3)CH3 are chain isomers.
Are there the same number of chain isomers for each organic molecule?
No, as the number of carbon atoms increase, the number of possible isomers will increase.
What is position isomerism?
When functional groups are situated in different positions in the molecules. For example, CH3CH2CH2OH and CH3CH(OH)CH3 are position isomers.
Although isomers have the same molecular formula, they differ from each other in two ways, what are the two ways?
Their physical and chemical properties.
What is functional group isomerism?
When isomers have different functional groups and therefore belong to different homologues series. For example, CH3CH2CH2OH (an alcohol) and CH3CH2OCH3 (an ether) are functional group isomers.
What are the two types of stereoisomerism?
- Geometric/E-Z isomerism
- Optical isomerism
Why do alkenes form E-Z isomers?
Because the double bond means in order to rotate, 𝛑 bonds must be broken, therefore isomers exist as a result when different groups exist on the carbons.
If an alkene has a structure like Cab=Ccd, what condition must be met for there to be E-Z isomers?
a≠b+c≠d
What is the isomer called when same groups are on the same sides of the double bond?
Z, or cis isomer.
What is the isomer called when same groups are on opposite sides of the double bond?
E, or trans isomer.
How does the melting/boiling point of E and Z isomers compare with each other?
E isomers tend to have higher melting/boiling points than Z isomers cause E isomers have a more linear shape and this allow more intermolecular attraction and therefore requires more energy to break them.
