Structural isomerism
Introduced| English | Meaning |
|---|---|
| isomer/ˈaɪsəmə/ | A compound with the same molecular formula as another compound but a different arrangement of atoms. |
| structural isomerism/ˈstrʌktʃərəl ˈaɪsəmərɪzəm/ | Isomerism where the atoms are connected in different orders. |
| chain isomerism/tʃeɪn ˈaɪsəmərɪzəm/ | The carbon chain is branched in different ways (e.g. butane vs 2-methylpropane). |
| positional isomerism/pəˈzɪʃənl ˈaɪsəmərɪzəm/ | The functional group is on a different carbon (e.g. propan-1-ol vs propan-2-ol). |
| functional group isomerism/ˈfʌŋkʃənl ɡruːp ˈaɪsəmərɪzəm/ | The atoms form a different functional group (e.g. an alcohol vs an ether). |
Same formula, different molecule
- Isomers 异构体 have the same molecular formula but a different arrangement of atoms.
- In structural isomerism 结构异构, the atoms are joined in a different order.
- There are three kinds.
Structural isomerism lab
Compare molecules with the same formula but different structures.
Isomers are compounds with:
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Isomers share a molecular formula but differ in how the atoms are arranged.
Compounds with the same molecular formula but different structures are structural ______.
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Chain, position and functional-group isomerism.
The three kinds
- chain isomerism 链异构 — the carbon chain is branched in different ways (e.g. butane vs 2-methylpropane).
- positional isomerism 位置异构 — the functional group is on a different carbon (e.g. propan-1-ol vs propan-2-ol).
- functional group isomerism 官能团异构 — the atoms form a different functional group (e.g. an alcohol vs an ether).
Cis and trans isomers of but-2-ene differ by which side the methyl groups sit
Chain isomerism is when:
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Chain isomers differ in how the carbon skeleton branches (e.g. butane vs 2-methylpropane).
Positional isomerism is when:
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Positional isomers have the same group on a different carbon (e.g. propan-1-ol vs propan-2-ol).
An alcohol and an ether with the same molecular formula are an example of:
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They have the same atoms arranged into a different functional group — functional group isomerism.
Match each kind of structural isomerism.
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Each item links the term to its correct meaning.
Three kinds of structural isomer
- Chain isomers differ in the carbon skeleton.
- Position isomers differ in where the functional group sits; functional-group isomers differ in the group itself.
A chiral carbon gives two non-superimposable mirror images (enantiomers)
Same formula, different properties
- Structural isomers share a molecular formula but can have very different properties.
- Always check you have drawn genuinely different connectivities, not the same molecule rotated.
You've got it
- isomers = same molecular formula, different arrangement of atoms
- structural isomerism = atoms joined in a different order, in three kinds:
- chain (different branching), positional (group on a different carbon), functional group (different group)