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Nomenclature

IUPAC nomenclature for organic chemistry

What is IUPAC nomenclature?

• A systematic method of naming organic chemical compounds as recommended by the International Union of Pure and Applied Chemistry (IUPAC).
• It provides an unambiguous structure.
• Official IUPAC naming recommendations are not always followed in practice, and the common or trivial name may be used.

Main chain and alkyl group

names

Main chain names Name # of Carbons Name # of Carbons meth ane 1 hex ane 6 eth ane 2 hept ane 7 prop ane 3 oct ane 8 but ane 4 non ane 9 pent ane 5 dec ane 10

Name Alkyl group names

of

Carbons Name^

of

Carbons meth yl 1 but yl 4 eth yl 2 pent yl 5 prop yl 3 Hex yl 6

Group (CH 3 ) 2 CH– (CHCH^3 ) 22 – CH CH 3 CH 2 CH(CH 3 )– (CH 3 ) 3 C– Name Isopropyl Isobutyl sec -Butyl tert -Butyl

Example

• Longest chain/main chain:
  • 7 carbons (circled)
  • Name: heptane
• Side chain groups:
  • 1-carbon group at position 3
  • Name: 3-methyl
  • 2-carbon group at position 4
  • Name: 4-methyl

Answer:

4-ethyl-3-methylheptane

Example

• Answer:
• 1-ethyl-2-methylcyclohexane

Answer:

cyclopropylcyclopentane

naming alkenes and alkynes

• -Ene suffix for alkene and -yne suffix for alkyne
• The root chain must be the longest chain that includes both carbon atoms of the double bond
• Number the root chain from the end nearest a double bond carbon atom (or triple bond carbon atom)
• The smaller of the two numbers designating the carbon atoms of the double/triple bond is used as the locator of alkenes/alkynes

Naming organic halides

• Same naming rules as before
• Halide substituents are named as fluoro (-F), chloror (-Cl), bromo (-Br), or iodo (-I)

Answer:

2-chloropropane

Example:

Naming Alcohols

• Drop the – ane ending of the parent compound and adding – ol
• When there’s a higher priority group present, -OH can be named as a substituent using the name hydroxy

Answer:

3-methyl-1-butanol

Example:

Naming aldehydes and ketones

• Aldehydes are named by dropping the – e of the parent name and adding – al
• The substituent name for aldehyde group is formyl
• When one or more – CHO groups are attached to the ring, the ring is named followed by carbaldehyde
• Ketones are named by dropping the – e ending and adding – one
• The substituent name is oxo

Examples

• Answer:
• 2-methylpropanal

Answer:

3-oxohexanal

Examples

• 4-methyl-2- pentamine
• N-methylethanamine
• N-ethyl-N- methylpropanamine

Naming carboxylic acids

• Carboxylic acids are named by dropping the – e ending and adding the – oic acid
• The substituent name for a – COOH group is carboxy

Answer:

2-chlorocyclopentanoic acid

Example:

Examples

• Answer:
• Butanoyl chloride

Answer: Ethanoic propanoic anhydride

Answer: Methyl ethanoate (common name: acetate)

Answer: ethanamide

References

• For more detailed rules and examples including common naming rules, please consult the organic chemistry by wade textbook
• Workshop prepared by Qing Wang