ALKANE

• Alkanes


  Also called paraffins<|>Saturated hydrocarbons
• Saturated hydrocarbon


  • A compound consisting entirely of hydrogen and carbon, composed entirely of single bonds
• Hydrocarbon


  • A compound consisting only of carbon and hydrogen atoms
• Alkanes are used in a number of industrial applications and are found in natural gas and petroleum
• Alkane structure


  General formula CnH2n+2<|>Adjacent atoms connected with sigma bonds and form tetrahedral centers around the carbon atoms<|>A series of linked carbon atoms is known as the carbon skeleton or carbon backbone
• Skeletal structure


  • Carbon atoms not symbolized with a C, but represented by each end of a line or bend in a line
  • Hydrogen atoms not drawn if attached to a carbon
  • Other atoms besides carbon and hydrogen represented by their elemental symbols
• Writing expanded formula of alkanes

  1. Identify the number of carbon atoms

  2. Use the formula CnH2n+2 to determine the number of hydrogen atoms

  3. Draw the expanded structural formula
• Constitutional/structural isomers


  Hydrocarbons that have the same molecular formula but different structures<|>A carbon atom has bonded to more than two carbon atoms
• Constitutional isomers


  • n-butane
  • 2-methylpropane
• Alkyl group


  Formed by removing one hydrogen from the alkane chain<|>Stem changes from -ane to -yl to indicate an alkyl group
• IUPAC nomenclature for alkanes


  Identify the longest carbon chain<|>Add prefixes to indicate positions and names of substituents<|>Number the carbon atoms from the end nearest the substituents
• Alkane names and formulas

  • methane (CH4)
  • ethane (C2H6)
  • propane (C3H8)
  • butane (C4H10)
  • pentane (C5H12)
  • hexane (C6H14)
  • heptane (C7H16)
  • octane (C8H18)
  • nonane (C9H20)
  • decane (C10H22)
• IUPAC nomenclature for cycloalkanes


  1. For monosubstituted, ring supplies the root name and substituent is named as usual

  2. If substituent is large/complex, ring may be named as substituent on alkane

  3. For multiple substituents, list in alphabetical order and number to give lowest possible numbers

  4. Assemble name listing groups in alphabetical order with location numbers
• Stereoisomers


  Molecules with same formula and connectivity but different spatial orientation<|>Cycloalkanes have less freedom of movement than open-chain alkanes<|>Di-substituted cycloalkanes can exist as cis (on this side) or trans (across) stereoisomers
• Stereoisomers


  • cis-1,2-dibromocyclopentane
  • trans-1,2-dibromocyclopentane