Crash Course Organic Chemistry: IUPAC Naming

Introduction

• Speaker: Deboki Chakravarti
• Communication challenges due to regional language differences
• Importance of standard naming in chemistry to avoid confusion
• International Union of Pure and Applied Chemistry (IUPAC): Established in 1919 to standardize chemical nomenclature

Common Names vs. Systematic Names

• Many chemical names are based on appearance or origin (e.g., vanillin from vanilla beans)
• Common names can be fun but often uninformative and can vary regionally
• Examples: alcohol, ether, acetone, acetic acid
• Standard system required for clarity and structure identification

IUPAC Systematic Naming Rules

• **3 Basic Steps: **
  1. Find the longest carbon chain and give it a root name
  2. Identify the highest priority functional group and add its suffix
  3. Identify the substituents and their positions, add numbered prefixes to the root name

Root Names for Carbon Chains

• Root names based on the number of carbon atoms:
  • 1 (meth-)
  • 2 (eth-)
  • 3 (prop-)
  • 4 (but-)
  • Mnemonic: Monkeys Eat Purple Bananas
• Root names resembling geometric shapes for chains 5-12:
  • 5 (pent-)
  • 6 (hex-)
  • 7 (hept-)
  • 8 (oct-)
  • 9 (non-)
  • 10 (dec-)
  • 11 (undec-)
  • 12 (dodec-)

Suffixes Based on Functional Groups

• Hydrocarbons:
  • Alkanes (single bonds) - suffix: -ane
  • Alkenes (double bonds) - suffix: -ene
  • Alkynes (triple bonds) - suffix: -yne
• Alkanes: Low energy, single bonds, e.g., hexane
• Alkenes: Double bonds, fun reactions - Include double bonds in longest chain for naming
  • Example: pent-1-ene
• Alkynes: Triple bonds; similar naming as alkenes
  • Example: oct-4-yne

Substituents Naming

• Hydrogens replaced by groups/atoms (e.g., carbon chains, halogens)
• Presence and Position: Add prefixes and numbers to the root name
• Naming conventions:
  • -CH3 substituent: methyl (example: 2-methylhexane)
  • Multiple same substituents: Use di-, tri-, tetra- (example: 2,4-dimethylhexane)
• **Halogens as Substituents: **
  • Chlorine (chloro-), Bromine (bromo-), Iodine (iodo-)
  • Example: 3-chloro-2,4-dimethylhexane
• Priority in Numbering:
  • Alkenes and alkynes prioritized over substituents for numbering
  • Examples:
    • 3-ethylpent-1-ene
    • 2,7-dimethyloct-4-yne

Complex Naming Example

• **Steps: **
  1. Root name based on the longest chain: hept-
  2. Highest priority functional group suffix: -ene and -yne
  3. Substituents with prefixes and positions: 4-bromo-3-methyl
• Complete Name: 4-bromo-3-methylhept-1-ene-6-yne

Conclusion

• Systematic names using IUPAC rules are crucial for clear scientific communication
• Episode conclusion: understanding basic steps and rules for systematic naming
• Next episode hint: systematic names with functional groups containing heteroatoms