What systematic names describe these molecules accordingly?

Question

the molecules are five sided with three lines in them.
two of the molecules have the reversible arrow between them.
Two of the molecules have the resonance arrow between them.
Is reversible and resonance the systematic name?
Is the difference between them just the electron patterns.
Any help would be appreciated
Thanks

Answer 1

It seems rather that these are six-sided hexagons with three alternating double bonds, =. That would be benzene. The reversible two arrows express the idea that the molecule changes rapidly between 1,3,5-cyclohexatriene and 2,4,6-cyclohexatriene. The double-headed single arrow, <===>, expresses the idea that the two structures are in resonance with one another. This means there is only one structure with 1-1/2 bonds between each C.