What are the possible isomeric structures of chlorobutene $(\ce{C4H7Cl})?$

I've come up with seven:

  • cis-1-chlorobut-1-ene
  • trans-1-chlorobut-1-ene
  • 2-chlorobut-1-ene
  • 3-chlorobut-1-ene
  • 1-chlorobut-2-ene
  • cis-2-chlorobut-2-ene
  • trans-2-chlorobut-2-ene
  • 1
    $\begingroup$ I can think of nine isomers. $\endgroup$ Feb 20, 2016 at 10:13
  • $\begingroup$ Can you please suggest the two isomers I'm missing? $\endgroup$
    – Rafat
    Feb 20, 2016 at 10:26
  • $\begingroup$ Wolfram Alpha can find the isomers of a given formula, quite nicely as well. $\endgroup$ Feb 20, 2016 at 20:09
  • $\begingroup$ @AliCaglayan Quite nicely except that it misses two of them? (2 and 3 from orthocresol's figure in my answer) I assume that it is simply extracting from a database except that surely 1-Chloro-1-methylcyclopropane is in any reasonable db? Weird. $\endgroup$
    – gilleain
    Feb 21, 2016 at 9:51
  • 1
    $\begingroup$ @gilleain I am having a hard time finding any literature on 1-Chloro-1-methylcyclopropane or 1-Chloro-2-methylcyclopropane which might mean that WA has not included it because there is no data on it? $\endgroup$ Feb 24, 2016 at 13:18

1 Answer 1


There are 12 different constitutional isomers:


There is also the further possibility of stereoisomerism in some of the compounds above.

  • 3: Two diastereomers (cis- and trans-) are possible.
  • 7, 8, 9: Geometrical isomerism is possible in these alkenes.
  • 11: C-3 (the carbon with the chlorine) is a chiral centre, which leads to two possible enantiomers.

That makes a total of 17 possible isomers.

  • 2
    $\begingroup$ And that's not counting the cis/trans things. $\endgroup$ Feb 20, 2016 at 12:33
  • $\begingroup$ I hope I didn't miss anything out. $\endgroup$ Feb 20, 2016 at 14:54
  • $\begingroup$ @orthocresol much better answer than mine! Should be a way to transfer answers, I guess. Thanks $\endgroup$
    – gilleain
    Feb 20, 2016 at 15:02
  • $\begingroup$ Well, you did the work finding the 12 constitutional isomers, I just touched it up a bit :) $\endgroup$ Feb 20, 2016 at 15:11

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