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Pretty simple question here.

How many enantiomers are there for the structure $\ce{CH3CH=CHCH(CH3)CH2CH3}$?

On the one hand, there is just one chiral centre so one would suggest $2$. On the other hand, there is some E/Z cis/trans isomerism at play leading to four distinct stereoisomers.

I made a sketch:

Displayed formulae of stereoisomers

If I'm not mistaken, $(A)-(D)$ are distinct molecules. Let's say we favour $(A)$. Would we say that the only enantiomer of $(A)$ is $(B)$, or would we say that all of $(B),(C),(D)$ are enantiomers of $(A)$?

I ask because I have been hearing some confused messages from my chemistry teacher and for a question as specific as this, I could not find a satisfactory online discussion. I would personally count them all as different enantiomers since it is truly a different arrangement of atoms in space and it is reasonable to suppose that all of them have slightly different optical properties.

What would you say?

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    $\begingroup$ I think there is a H missing in the formula. / On the matter at hand, I'd say there are two sets of enantiomers (a and b, c and d). Everything else would be ambiguous at best. Enantiomers always come in pairs, so the answer is pretty much always two and only differs in the number of sets. $\endgroup$ Commented May 2, 2023 at 19:51
  • $\begingroup$ @Martin-マーチン There is a missing $H$ yes. Thank you for sharing your thoughts $\endgroup$
    – FShrike
    Commented May 2, 2023 at 20:10
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    $\begingroup$ Please edit the question to fix the error. $\endgroup$ Commented May 2, 2023 at 22:47
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    $\begingroup$ A chiral atom has four different groups attached. Enantiomers refer to a comparison between two stereoisomers. So enantiomers are steroisomers that are non-superimposable mirror images (=chirality). While enantiomers contain chiral centers in the molecules, but not all stereoisomers of a molecule are enantiomers of each other. It's such an uncomfortably boggling jargon - always drawing them helps ! $\endgroup$
    – bonCodigo
    Commented May 3, 2023 at 5:02
  • $\begingroup$ @bonCodigo So you seem to be suggesting only $(A),(B)$ and $(C),(D)$ are enantiomers. $\endgroup$
    – FShrike
    Commented May 3, 2023 at 7:12

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