A LITTLE LIGHTBULB MOMENT
Organic chemistry: structure and stereochemistry
Constitutional isomers
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Same formula, different atom wiring
The idea behind the cue
Constitutional isomers share a molecular formula but differ in which atoms are connected to which. The difference is in connectivity, not 3D arrangement. They can have noticeably different physical and chemical properties.
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Short & simple
Same formula, different atom wiring
Acronym
FC — Fluffy Cupcakes.
Story
Two toy trains both have six cars, but one has the caboose on the front track and the other has it in the middle. Same cars, different connections, so they behave differently.
Connect the pieces
- F (Fluffy) → Formula: Constitutional isomers share the same molecular formula.
- C (Cupcakes) → Connectivity: Their atoms are connected differently, so they are not stereoisomers.
- Fluffy · Formula: Constitutional isomers share the same molecular formula.
- Cupcakes · Connectivity: Their atoms are connected differently, so they are not stereoisomers.
Know the limits
Does not include stereoisomers, which keep the same connectivity.
Further reading · OpenStax science and mathematics textbooks ↗Check your understanding
Which pair has the same molecular formula but different atom connectivity?
A. Conformers
B. Constitutional isomers
C. Enantiomers
D. Diastereomers
Reveal explanation
Constitutional isomers
Constitutional isomers differ in bonding pattern while keeping the same formula. The other options all preserve connectivity.