Hydrocarbons (Alkanes)

An important class of binary compounds are the hydrocarbons. As the name implies hydrocarbons consist of only hydrogen and carbon atoms. There are thousands of possible hydrocarbon molecules. However, the simplest type are called "alkanes". Alkanes have the formula CnH2n+2, where n = 1,2,3 etc.. For example for n=1 we have CH4, for n=2 we have C2H6 etc.. Naming these hydrocarbons is simple:

  • For n=1-4 the names have historical importance and must therefore be memorized.
  • For n > 4 the first part of the name gives the number of carbon atoms (e.g., n=5 is pent-, n=6 is hex- etc.)
  • the lastpart of the name ends with "- ane"

(state at room temperature)
 CH4 (gas)  methane  
 C2H6 (gas)  ethane  
 C3H8 (gas)  propane  
 C4H10 (gas)  butane  
 C5H12 (liquid)  pentane  pent = 5
 C6H14 (liquid)  hexane  hex = 6
 C7H16 (liquid)  heptane  hept = 7
 C8H18 (liquid)  octane  oct = 8
 C9H20 (liquid)  nonane  non = 9
 C10H22 (liquid)  decane  dec = 10
 C18H38 (solid)  octadecane  octadec = 18

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C101 Class Notes
Prof. N. De Leon