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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