allenes

例句：

1. 1. The alkenes are a type of unsaturated hydrocarbons.
   烯烃是一种不饱和的碳氢化合物。
2. 2.Alkenes play a crucial role in the polymerization process.
   烯烃在聚合过程中起着至关重要的作用。
3. 3. The alkenes undergo a reaction that leads to the formation of new compounds.
   烯烃经历一种反应，导致形成新的化合物。