Here we have to get the possible isomers of hexene C₆H₁₂ which have no branching and cis, trans form.
The alkene isomers those are possible for C₆H₁₂ without any branch and e/z isomers is 1-hexene.
The isomers are possible without any branch for C₆H₁₂ may be 1-hexene, 2-hexene and 3-hexene.
But without e/z isomers mean the structure should not have any cis, trans form.
Now the 2-hexene and 3-hexene both have cis, trans isomerism. Only 1-hexene will not have any branch chain and e/z isomers.
Thus the name of the alkene isomer having C₆H₁₂ formula is determined.