Propylene due to the molecular structure.

there cannot be a cyclic compound formed with ethene, i.e a 2 carbon compound. smallest cyclic hydrocarbon is cyclopropane (C3H6), smallest cyclic alkene is cyclopropene (C3H4), and smallest alkyne is Cyclopropene (C3H2)

9

Formula: C3H6

No

Propane is C3H8
Cyclopropane is C3H6..................Therefore they have different chemical compositions and are completely different molecules and not isomers.

Propene C3H6 is however an isomer of cyclopropane