Isomers with molecular formula C₄H₇Cl
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.