Why 1-ethenyl-3-ethyl-5-ethynylbenzene has that name? I would priorized these funtional groups based on two options (following the ciclohexane rules):


Molecular weight
Representing each pi bond as a alkane branch. e.g. Ethenil as a isopropil backbone.


But, none of these option works. Why this molecule has that name?
Ordering substituents by complexity has been abandoned long ago (before 1979) in favor of the much simpler alphabetic order. Here, ethenyl &lt; ethyl &lt; ethynyl.

Note, however, that simple substituents are ordered alphabetically before adding a multiplicative prefix, which means that "dimethyl" is ordered as "methyl".

Complex substituents are ordered by their first letter, e.g. isopropyl (I), dimethylphenyl (D)