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The alkyl radical and IUPAC naming

The alkyl radical and IUPAC naming

Point 7 of 9 — Introduction to Organic Chemistry, Wöhler’s Theory and AlkanesQuestion bank: 0 questions (0 with pictures)

07 The alkyl radical and IUPAC naming

  • Removing one hydrogen atom from an alkane gives the alkyl radical R–, written CₙH₂ₙ₊₁–: CH₃– methyl, C₂H₅– ethyl, C₃H₇– propyl.
  • Steps of IUPAC naming:
    1. Choose the longest continuous carbon chain — it gives the parent name (meth-, eth-, prop-, but-, pent-, hex-… + -ane).
    2. Number the chain from the end nearest the first branch so that substituents get the lowest possible numbers.
    3. Name the substituents (alkyl groups, halogens as fluoro/chloro/bromo/iodo) with their numbers; use di-, tri-, tetra- for repeated groups, and separate numbers by commas and numbers from words by hyphens.
    4. Arrange substituents alphabetically, then give the parent name.
  • Examples:
    • CH₃–CH₂–CH₂–CH₃ → butane.
    • (CH₃)₂CH–CH₃ → 2-methylpropane (common name: isobutane).
    • CH₃–CHCl–CH₂–CH₃ → 2-chlorobutane.
    • CH₃–CH(CH₃)–CH₂–CH₃ → 2-methylbutane, never "3-methylbutane" — the lower number wins.

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