Multivalent substituent groups

Multivalent substituent groups of acyclic hydrocarbons are designated by attaching the suffixes. ..idene and. ..idyne to the name of the corresponding monovalent group insofar as the free valences are at the same C atom. Multiple occurrence of such structural elements is taken into account with suitable multiplicative infixes. Methylene, =CH2 or -CH2-, is retained as trivial name the group =CH- is sometimes still called methine or methyne. 

Hydrocarbon chains with free valences at each terminal C atom are frequently still called trimethylene-, tetramethylene-, etc. instead of alkane-l-n -diyl groups, the systematically correct designation. Unsaturated substituent groups of this kind are named by replacing the terminal syllable. .. ene with. .. enylene. The trivial terms ethylene for -CH2-CH2-, propylene for H3C-CH-CH2-, and vinylene for -CH=CH- are still frequently 

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Other multivalent bridges are treated in the same way as the corresponding substituent groups. 

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