IUPAC Naming

IUPAC Naming System

Naming organic compounds using the IUPAC system follows four key steps:

1. Identify the main functional group and assign it the highest priority.
2. Find the longest carbon chain that includes this group, numbering it to give the lowest possible number to the priority group.
3. List and number any substituents (branches), arranging them alphabetically in the name.
4. Specify stereochemistry if applicable (E/Z, R/S, cis/trans, etc.).

The final IUPAC name follows this structure:

# - Stereochemistry - # - Prefix F.G(s). - # - Substituent(s) - Parent Chain - Multiple Bond - Suffix F.G.

Examples of IUPAC naming:

• (E)-4-Hydroxy-3-methylpent-2-en-1-one
• (R)-3,4-Dihydroxy-5-methylcyclohex-2-en-1-one
• (Z)-4-Bromo-3-methylhex-2-en-1-ol
• (S)-2,5-Diamino-3-hydroxy-4-methylhexanoic acid
• (E)-5-Ethyl-4-hydroxy-3,6-dimethylhept-2-en-1-one
• (R,E)-3,5-Dimethoxy-4-methylhex-2-enal
• (S)-4-Ethyl-2-hydroxy-3,5-dimethylhexanoic acid
• (E)-2-Bromo-5-ethyl-4-methylhex-2-enamide
• (Z)-3,6-Dihydroxy-4,8-dimethylundec-2-enoic acid

This method applies to all organic compounds.

Prefix Table (Carbon Chain)

Suffix Table (Bond Types)

Functional Groups

The below table is in decreasing order of priority.

Additional Naming Rules & Notes

1. Multiple Functional Groups:

   • The highest priority group gets the suffix.

   • All other functional groups are named as prefixes.

   • Example 1:

     • Compound: $\ce{CH3CH(OH)CH2COOH}$
     • IUPAC Name: 3-Hydroxybutanoic acid
     • Priority Order: Carboxyl ($\ce{-COOH}$) > Hydroxyl ($\ce{-OH}$)

   • Example 2:

     • Compound: $\ce{CH3CH(Br)CH(OH)CH3}$
     • IUPAC Name: 2-Bromo-butan-3-ol
     • Priority Order: Hydroxyl ($\ce{-OH}$) > Halo ($\ce{-Br}$)

2. Numbering of Chains:

   • The longest continuous chain is chosen.
   • The functional group gets the lowest possible number.

3. Multiple Bonds (Double & Triple):

   • If both double $\ce{C=C}$ and triple $\ce{C#C}$ bonds are present, the double bond is given priority in numbering.

4. Cyclic Compounds:

   • Prefix: Cyclo-
   • Example: Cyclohexanol → $\ce{C6H11OH}$.

Exceptions & Special Cases

1. Common Names Used

Some compounds have retained their common names as IUPAC-approved names.

2. Modified Functional Groups Naming

Some groups have unique suffixes or prefixes in IUPAC.

3. Aromatic System Naming Exceptions

Some aromatic compounds have special historical names.

4. Special Aliphatic Naming Exceptions

Some chains do not follow usual alkane naming.

6. Special Amino Acid Naming

Amino acids often do not follow usual amine and acid naming.

7. Special Oxoacid Naming

Some oxoacids have irregular naming.

Key Takeaways

• Some common names are still IUPAC-approved (e.g. acetone, toluene, glycerol).
• Carboxylic acids and esters retain some historical names.
• Aromatic compounds often have non-systematic names.
• Amino acids and oxoacids follow special conventions.

References

• Wikipedia: IUPAC Nomenclature

Common Names

Organic Chemistry: Common Names

Common names are often used colloquially and in everyday life but lack a systematic approach like IUPAC nomenclature. These seemingly arbitrary names can hinder your understanding and ability to solve problems, as exam questions may use common names that you might not be familiar with. To overcome this, it’s essential to familiarize yourself with common names and their corresponding structures.

Resources

[!Orange] Note This list may and will be updated in future as I add more resources.

PDFs

1. Common Names Google Drive Collection:
   • PDFs I collected that included common names and their corresponding structures. (Sorry, but I didn’t consider noting the sources of some of these PDFs at that time.)

Online Courses

1. Khan Academy Organic Chemistry Course:
   • Khan Academy is the best. (My favourite)

Websites

1. IUPAC Nomenclature of Organic Compounds:
   • Full text explaination of IUPAC Nomenclature of Organic Compounds.

Memorization Techniques

To effectively memorize common names, try these strategies:

1. Spaced Repetition:
   • Revise common names at increasing intervals to reinforce your memory.
2. Associations:
   • Link common names to familiar objects or concepts to enhance recall.
3. Flashcards: (Totally Optional)
   • Create flashcards with common names on one side and structures on the other. Try out Anki if you wanna make them digitally.