I am trying to name the molecule pictured below. I thought it would be 5-bromo-4-isopropyl-2-methylhex-2-ene, but googling that name does not show any results, which makes me think it is not right. Can anyone suggest what I might be doing wrong?


  • $\begingroup$ This is how I would be happy to name it, but there are IUPAC rules that you need to look up about systematic naming. You could look at ChemSpider and try the molecular formula; you will find very many compounds, however. $\endgroup$ – porphyrin Sep 14 '18 at 8:53
  • $\begingroup$ The name is really not the correct one, from two major reasons - substituents given by prefix, like methyl and bromo, or bromoethyl, have the same priority (there's no priority), and because of rules P-45.2.1, P-45.2.2 $\endgroup$ – mykhal Sep 14 '18 at 11:34

The suggested name 5-bromo-4-isopropyl-2-methylhex-2-ene is not wrong; however, it is not the preferred name according to current IUPAC recommendations.

Since the compound has a double bond but no principal characteristic group that would be expressed as a suffix, it is clear that the parent structure is a 2-methylhex-2-ene. However, there is a choice between two different principal chains, which lead to different names:

  • 5-bromo-2-methyl-4-(propan-2-yl)hex-2-ene and
  • 4-(1-bromoethyl)-2,5-dimethylhex-2-ene

Both possible chains have two additional (but different) substituent groups in the same positions; therefore, the usual nomenclature criteria related to number and location of substituent groups do not help. Finally alphabetical order is used to identify the preferred name as 4-(1-bromoethyl)-2,5-dimethylhex-2-ene.

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