Nomenclature of Alkanes and the IUPAC System

IUPAC System

  • Name of an alkane with an unbranched chain of carbon atoms   * Prefix that indicates the number of carbon atoms   * Suffix -ane to show that the compound is a saturated hydrocarbon (alkane)
  • Name of an alkane with a branched chain   * Parent name that indicates the longest chain of carbon atoms in the compound   * Substituent names that indicate the groups bonded to the parent chain     * Give each substituent a number to indicate the carbon atom to which the substituent is bonded - use a hyphen to connect the number to the name     * If there's one substituent, number the parent chain from the end that gives the substituent the lower number     * If there are two or more identical substituents, number the parent chain from the end that gives the lower number to the substituent encountered first       * The number of times the substituent occurs is indicated by the prefix di, tri, etc; use a comma to separate position numbers     * If there are two or more different substituents, list them in alphabetical order and number the chain from the end that gives the lower number to the substituent encountered first       * If there are different substituents in equivalent positions on opposite ends of the parent chain, give the substituent that comes first in the alphabet the lower number     * Alphabetize the name of the constituents and then add the prefixes di, tri, etc     * When there are two or more parent chains of equal length, choose the parent chain with the greater number of constituents
  • Alkyl group: a substituent group derived from an alkane by the removal of a hydrogen atom   * Commonly represented by the symbol R-   * Named by dropping the -ane and adding -yl
  • Substituents with unbranched chains are named by replacing the -ane with -yl 

General IUPAC System

  • The name given to any compound with a chain of carbon atoms consists of 3 parts: prefix, infix, and suffix   * Prefix: indicates the number of carbon atoms in the parent chain   * Infix: indicates the nature of the carbon-carbon bonds in the parent chain     * -an-:all single bonds     * -en-: one or more double bonds     * -yn-: one or more triple bonds   * Suffix: indicates the class of the compound     * -e: hydrocarbon     * -ol: alcohol     * -al: aldehyde     * -one: ketone     * -oic acid: carboxylic acid

Classification of Carbon and Hydrogen Atoms

  • Primary carbon: carbon bonded to one carbon

  • Secondary carbon: carbon bonded to 2 carbons

  • Tertiary carbon: carbon bonded to 3 carbons

  • Quaternary carbon: carbon bonded to 4 carbons

  • Primary hydrogen: hydrogen bonded to a primary carbon

  • Secondary hydrogen: hydrogen bonded to a secondary carbon

  • Tertiary hydrogen: hydrogen bonded to a tertiary carbon

  • Quaternary hydrogen: hydrogen bonded to a quaternary carbon

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