Organic Names Functional Group Structures Hydrocarbons compounds  Elmhurst College
Root Name Position Numbers  Inorganic Groups  Chemistry Department
Functional Group Names Carbon Branches Final Name  Virtual ChemBook



Root names give the number of carbons in the longest continuous chain. Root names are used with various "endings" to indicate branches, type of bonds between carbons, and functional groups.

The following list gives the most basic root the with normal hydrocarbon alkane endings for the number of carbons in the longest continuous chain. MEMORIZE THIS LIST.

Example: root = "hex" + alkane ending = "ane" = hexane. See on left.

 The longest continuous chain of carbons is found by tracing through carbons without lifting your pencil or "backing up". Hydrogens, although written between carbons in condensed formulas, do not break the carbon chain. An oxygen, nitrogen, or sulfur between carbons DOES break the continuous carbon chain. The longest continuous chain may turn in any direction.
 Example lower left: Initially you may think that the six carbons in a straight line is the longest chain. Look again and count the red carbons to find seven carbons as the longest chain to give heptane as the root name.
 No. of

 Root Name




 CH4  CH4


 C2H6  CH3CH3


 C3H8  CH3CH2CH3


 C4H10  CH3CH2CH2CH3


  C5H12  CH3CH2CH2CH2CH3