I don't know, but I think so, because if you have double bonds in a ring of six C atoms, then it is normally aromatic. That means you have three double bonds (to be exact, actually six delocalized π-electrons in one circular electron cloud), or you have heteroatoms (like N or O) in the ring.
If none of the above is the case the ring should only contain single bonds like in case of cyclohexane.
... and I think I was wrong yesterday night (maybe it was already too late to think clearly :), because the molecule Y is obviously 1,3-Cyclohexadiene, thus of course it need not to be sketched wrongly.
In this case the red color doesn't point out at any mistake, but that it is not a single bond.
It is possible that we should count the double bonds, or otherwise all bonds which are not single bonds (all multiple bonds).
I don't know, but I think so, because if you have double bonds in a ring of six C atoms, then it is normally aromatic. That means you have three double bonds (to be exact, actually six delocalized π-electrons in one circular electron cloud), or you have heteroatoms (like N or O) in the ring.
If none of the above is the case the ring should only contain single bonds like in case of cyclohexane.
I was also thrown off by that...
... and I think I was wrong yesterday night (maybe it was already too late to think clearly :), because the molecule Y is obviously 1,3-Cyclohexadiene, thus of course it need not to be sketched wrongly.
In this case the red color doesn't point out at any mistake, but that it is not a single bond.
It is possible that we should count the double bonds, or otherwise all bonds which are not single bonds (all multiple bonds).
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The original image is here. The red highlight is there for teaching purposes, and likely irrelevant when taken out of context (in this puzzle).
Little hint: the amount and type of bond counts