Overview
This lecture introduces cycloalkanes, focusing on their structure, naming conventions, and examples for identifying and naming cycloalkane compounds.
Cycloalkanes: Structure and Function
- Cycloalkanes are hydrocarbons with carbon atoms arranged in closed ring structures and only single bonds.
- They can consist of one or more interconnected rings.
- Cycloalkanes are used as solvents and in biomolecules, antiviral drugs, and anesthetics.
Naming Cycloalkanes
- Cycloalkanes are named like alkanes, but with the "cyclo-" prefix added to the root.
- The ring structure is treated as the parent (longest) carbon chain.
- If the ring is not the longest chain, it is named as a substituent ending in "-yl" (e.g., cyclopropyl).
- The root name reflects the number of carbons in the ring (e.g., cyclohexane = six carbons).
Naming with Substituents
- Name substituents (groups attached to the ring) as prefixes; use alphabetical order.
- Number the ring so substituents get the lowest possible numbers.
- For multiple substituents: assign the first position to the alphabetically first group, then assign the next-lowest numbers.
- Example: 1-ethyl-3-methylcyclohexane indicates ethyl and methyl groups at carbons 1 and 3 of cyclohexane.
Examples
- A six-carbon ring with ethyl and methyl substituents is named 1-ethyl-3-methylcyclohexane.
- A five-carbon ring with ethyl and methyl groups is named 1-ethyl-2-methylcyclopentane.
Key Terms & Definitions
- Cycloalkane — a saturated hydrocarbon with carbon atoms arranged in a ring.
- Substituent — a group attached to the main ring or chain, named as a prefix.
- Cyclo- Prefix — added to the root name to indicate a ring structure (e.g., cyclopentane).
- Parent Chain — the longest continuous carbon chain, here typically the ring itself.
Action Items / Next Steps
- Practice naming cycloalkanes and their derivatives using provided examples.
- Focus on recognizing the parent ring structure and applying correct numbering and alphabetical order for substituents.