cyclic  
adjective uk/ˈsɪk.lɪk/ /ˈsaɪ.klɪk/ us/ˈsɪk.lɪk/ /ˈsaɪ.klɪk/
  (CHEMISTRY)      
 chemistry specialized环状结构的 
relating to a structure of molecules (= the simplest units of a chemical substance) that contain atoms in closed rings
  We would see a cyclic molecule such as cyclohexane A as a flat ring with the hydrogen atoms around it.
 His work on the structure of the metal carbonyls had suggested that a cyclic structure was improbable. 他对金属羰基结构的研究表明,环状结构是不可能的。 
 - More examples
 - A traditional jet fuel has more straight- and branched-chain hydrocarbon molecules called alkanes, whereas the new fuel has more cyclic molecules that look like pairs of rings.
 - The reaction produces a cyclic sulfonium compound.