Naming of Alkenes
Ethene (Ethylene) CH2=CH2
Propene (Propylene) CH2=CH-CH3
From the third member (butene) of the alkene family onward, there is a need to specify the location of the double bond to recognize the correct structure denoted by the name. When naming alkenes, the numbering should begin from the carbon chain end which gives the double bond position the lowest number.
Watch the numbering of carbons in the following examples.