Natura - nature
   actualia - actual entities
     Mundus Plinius - physical world
       naturalia - natural bodies
         "crystal-kingdom"
           chemical substances
             chemical compounds
               Class hydrocarbons [CxHy] - compounds consisting of carbon and hydrogen only
                 Class olefins
                   Class alkenes [CnH2n] - unsaturated acyclic hydrocarbons having one double bond
                     1 ethylene [C2H4; CH2=CH2]
                     2 propylene [C3H6; CH3CH=CH2]
                     3 3-methyl-1-butene [C5H10; CH2=CHCH(CH3)CH3]
                     4 2-pentene [C5H10; CH3CH=CHCH2CH3]
                     5.1 5,5-dimethyl-1-hexene [C8H16; CH2=CH[CH2]2C(CH3)2CH3]
                     5.2 2-hexene [C6H12; CH3CH=CH[CH2]2CH3]