# Isomers with molecular formula C4H7Cl

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
• I can think of nine isomers. – Klaus-Dieter Warzecha Feb 20 '16 at 10:13
• Can you please suggest the two isomers I'm missing? – Rafat Feb 20 '16 at 10:26
• Wolfram Alpha can find the isomers of a given formula, quite nicely as well. – Ali Caglayan Feb 20 '16 at 20:09
• @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. – gilleain Feb 21 '16 at 9:51
• @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? – Ali Caglayan Feb 24 '16 at 13:18

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.

• And that's not counting the cis/trans things. – Ivan Neretin Feb 20 '16 at 12:33
• I hope I didn't miss anything out. – orthocresol Feb 20 '16 at 14:54
• @orthocresol much better answer than mine! Should be a way to transfer answers, I guess. Thanks – gilleain Feb 20 '16 at 15:02
• Well, you did the work finding the 12 constitutional isomers, I just touched it up a bit :) – orthocresol Feb 20 '16 at 15:11