#alkene__olefine__olefin  any unsaturated aliphatic hydrocarbon
  supertype:  aliphatic_compound__aliphaticcompound  organic compound that is an alkane or alkene or alkyne or their derivative
  subtype:  ethylene__ethene  a flammable colorless gaseous alkene; obtained from petroleum and natural gas and used in manufacturing many other chemicals; sometimes used as an anesthetic

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