Lecture: Naming Alkanes (Nomenclature of Alkanes)

Introduction

• Topic: Nomenclature of alkanes
• Structure: Begins with naming alkanes, then moves to 3D conformations
• Presenter: Chad from Chad’s Prep
• Content: Organic chemistry playlist. Focuses on making science understandable.

Overview of Alkanes

• Definition: Molecules with carbon and hydrogen only; no carbon-carbon double or triple bonds.
• Comparison: Different from alkenes (double bonds) and alkynes (triple bonds).

Naming Alkanes

• Parent Chain: Longest continuous carbon chain.
  • Example: Bond line structure. Identify longest chain; anything outside is a substituent.
• Suffix: "-ane" for alkanes.
• Numerical Prefixes: Indicate number of carbons.
  • 1: Meth-, 2: Eth-, 3: Prop-, 4: But-, 5: Pent-, 6: Hex-, 7: Hept-, 8: Oct-, 9: Non-, 10: Dec-, 11: Undec-, 12: Dodec-
  • Mnemonic: Meth, Eth, Prop, But (Me Eat Peanut Butter)

Naming Substituents

• Ending: "-yl" for substituents.
  • Example: Methyl (CH3), Ethyl (C2H5), Propyl (C3H7)

Naming Strategy

• Format: Substituents first, parent chain last.
• Locators: Numbers indicate substituent positions, separated by hyphens.
• Multiple Substituents: Use prefixes (di-, tri-, etc.). Alphabetical order for different substituents.

Examples

1. Methylheptane (2-Methylheptane):

   • Longest chain: 7 carbons.
   • Methyl group at carbon 2.
   • Name: 2-Methylheptane.

2. Complex Example:

   • Longest chain: 7 carbons, decide based on more substituents.
   • Substituents: Ethyl and Methyl.
   • Name: 3-Ethyl-2-Methylheptane.

3. Cycloalkanes:

   • Ring structures, named with 'cyclo' prefix.
   • Mono-substituted cycloalkanes omit the '1'.
   • Example: Chlorocyclohexane (not 1-Chlorocyclohexane).

4. Disubstituted Cycloalkane:

   • Example: 1-Chloro-2-Methylcyclohexane.
   • Use alphabet to break ties.

5. Trisubstituted Cycloalkane:

   • Example: 4-Bromo-1-Chloro-2-Methylcyclohexane.
   • Always get lowest numbers first before using alphabet.

6. Parent Chain Not a Ring:

   • Example: 1-Cyclobutylhexane.
   • Chain is longer than ring; ring is a substituent.

Conclusion

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