Multiplicative infixes

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. 

Alkynes contain one or more triple bonds. They are named in a similar way to alkenes. The suffix used for alkynes is -yne. Ethyne is often called acetylene. Alkynes with one triple bond have the general formula Cn 2n-2-Multiple triple bonds are named using -diyne, -triyne, etc. The infix -ynyl- is used for functional groups composed of alkynes after the removal of a hydrogen atom. 

If the carboxylic acid contains a carbon-carbon double or triple bond, change the infix from -an- to -en- or -yn-, as the case may be, to indicate the presence of the multiple bond and show the location of the multiple bond by a number. 

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