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What would the name of this hydrocarbon be?

I thought it might have been $\ce{3-phenyl-1-butene}$, however, after searching through a number of chemical websites, I found that 3-phenyl-1-butene isn't the correct name (the structures coming up had the benzene ring attached at the 4th carbon from the $\ce{C-C}$ double bond).


2 Answers 2


First, by your logic, it would be 3-phenylbut-1-ene. Note that the 1 is right before the ene, indicating that is where the double bond is. It is a perfectly understandable name, one that many chemists would use for this compound.

The other way to name it is to consider it a substituted benzene. Then you get (but-3-en-2-yl)benzene. This is the preferred IUPAC name for the compound, because benzene is the base molecule by IUPAC priority rules (rule P-52.2.8 of the 2013 edition of the Blue Book: “Within the same heteroatom class and for the same number of characteristic groups cited as the principal characteristic group, a ring is always selected as the parent hydride to construct a preferred IUPAC name.”).

  • $\begingroup$ Thanks to @Loong for pointing out in chat that “(but-3-en-2-yl)benzene” is the correct name, not “3-buten-2-ylbenzene” $\endgroup$
    – F'x
    Commented Aug 11, 2016 at 11:26
  • $\begingroup$ Great to have you back! $\endgroup$
    – jonsca
    Commented Aug 11, 2016 at 23:10

(1-Methyl-allyl)-benzene is the correct IUPAC name. Benzene is the parent part of this hydrocarbon and 1-methy-allyl is the substituent. So, 3-phenyl-1-butene is wrong.

  • 1
    $\begingroup$ Please note that, according to current IUPAC nomenclature, the name ‘allyl’ is retained for general nomenclature only. Substitution is allowed, but not by alkyl or any other group that extends the carbon chain. Thus, the name ‘1-methylallyl’ is no longer a correct IUPAC name. (In the 1993 recommendations, the name ‘allyl’ was still retained for use with no limitation on substitution.) $\endgroup$
    – user7951
    Commented Aug 11, 2016 at 11:19

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