These are structural formulas of constitutional isomers of hexene, an alkene.
Both are acyclic, six-carbon chains, and they differ only in the position of the double bond. As constitutional isomers, both structures have the same molecular formula.
The first structure is of hex-1-ene (or 1-hexene).
The second structure is of (3E)-hex-3-ene [or (3E)-3-hexene].
Both structures have the molecular formula C₆H₁₂.
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