Lecture Notes: Chapter 4 - Cycloalkanes

Introduction to Cycloalkanes

• Cycloalkanes are cyclic structures of alkanes.
• Focus on stereochemistry and arrangement in 3D space.
• Examples include:
  • Prostaglandin: A hormone with ring structures.
  • Cortisone: A steroid with three six-member rings and one five-carbon ring.

Naming Cycloalkanes

• Cycloalkanes, also known as alicyclic compounds, are saturated cyclic hydrocarbons.
• General formula: CnH2n (compared to alkanes CnH2n+2).
• Naming involves adding "cyclo" before the alkane name.
  • Examples: Cyclopropane (3 carbon), Cyclobutane (4 carbon), etc.

IUPAC Naming Steps

1. Count carbons in the ring and the largest substituent.
2. Determine if the cyclic molecule or alkyl group is the parent.
3. Examples:
   • Methylcyclopentane: More carbons in cyclo (parent).
   • 1-Cyclopropylbutane: More carbons in alkyl (parent).

Substituent Numbering Rules

• Single substituent: Implicitly on first carbon.
• Multiple substituents: Number to achieve the lowest sum of substituent positions.

Examples

• 1,3-Dimethylcyclohexane vs. 1,5-Dimethylcyclohexane: Choose numbering that gives the lowest numbers (1,3 preferred).
• Cycloheptane Examples:
  • 2-Ethyl-1,4-Dimethylcycloheptane
  • Incorrect options include 1,2,6 or 3,1,4 ordering.
• Molecule Naming Practice:
  • 1-Isopropyl-2-Methylcyclohexane
  • 4-Bromo-1-Tertbutyl-2-Methylcycloheptane
  • 4-Bromo-1-1-1-Dimethylethyl-2-Methylcycloheptane

Additional Notes

• Alphabetizing rules for substituents with tert or sec prefixes.
• Importance of prioritizing by base group in complex substituents.

Conclusion of Video

• Reviewed naming conventions, substituent prioritization.
• Provided examples for practice and verification.