Nomenclature

Nomenclature is the systematic naming of organic compounds following specific rules to provide a unique and standardized way to identify and communicate the structure of molecules.

Rules for Naming Alkanes:

Identify the longest continuous carbon chain and use the appropriate suffix “-ane” to indicate it is an alkane.

(e.g. Ethane: CH₃─CH₃)

Number the carbon atoms in the chain to give the substituents the lowest possible numbers.

(e.g. 2-Methylpentane: CH₃─CH(CH₃)─CH₂─CH₂─CH₃)

If there are multiple substituents, use commas to separate the numbers, and arrange them alphabetically.

(e.g. 3-Ethyl-2,4-dimethylhexane: CH₃─CH₂─CH(CH₃)─CH₂─CH(CH₃)─CH(CH₃)─CH₃)

For identical substituents, use prefixes such as di-, tri-, tetra-, etc.

(e.g., 2,2,3-Trimethylbutane: (CH₃)₂C(CH₃)CH₂CH₃)

Rules for Naming Alkenes:

Identify the longest continuous carbon chain containing the double bond and use the suffix “-ene” to indicate it is an alkene.

(e.g., Ethene: CH₂═CH₂)

Number the carbon atoms in the chain to give the double bond the lowest possible numbers.

(e.g., 3-Octene: CH₃─CH₂─CH═CH─CH₂─CH₂─CH₂─CH₃)

If there are multiple double bonds, use the prefix “diene,” “triene,” etc., and locate them with numbers.

(e.g., 1,3-butadiene: CH₂═CH─CH═CH₂)

Rules for Naming Alkynes:

Identify the longest continuous carbon chain containing the triple bond and use the suffix “-yne” to indicate it is an alkyne.

(e.g., Eth-1-yne: HC≡CH)

Number the carbon atoms in the chain to give the triple bond the lowest possible numbers.

(e.g., 3-Hexyne: CH₃─CH₂─C≡C─CH₂─CH₃)

If there are multiple triple bonds, use the prefix “diyne,” “triyne,” etc., and locate them with numbers.

(e.g., 2,5-octadiyne: CH₃─C≡C─CH₂─C≡C─CH₂─CH₃)

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