I encountered this question in the Black Book of Organic Chemistry by Ashish Mishra while preparing for a college entrance exam.
According to the answer key the answer is 12. I have only managed to draw 11 possible structures.
If someone could help me find out the 12th structure it would be greatly appreciated. The structures I have drawn
In this the 1st, 2nd, 5th, and 6th structures are optically active, giving a total of $7+4 =11$ compounds.
PS: I used this to draw these structures. If there is more preferable way to upload structures let me know and I will update them.


1 Answer 1


The 7th structure is also optically active. (1S,2R)-1-(Chloromethyl)-2-methylcyclopentane is different from (1R,2S)-1-(chloromethyl)-2-methylcyclopentane.

(1S,2R)-1-(chloromethyl)-2-methylcyclopentane    (1R,2S)-1-(chloromethyl)-2-methylcyclopentane

  • $\begingroup$ The molecule (1S,2R) exists here. But the molecule (1R,2S) is not produced here. $\endgroup$
    – Maurice
    Commented Feb 3 at 16:45
  • $\begingroup$ @Maurice I believe both will form depending on which methyl group is chlorinated, is the answer not correct? $\endgroup$
    – Grimm
    Commented Feb 3 at 17:54
  • $\begingroup$ Yes, Grimm. Sorry ! It is correct. I had not thought about this possibility. Thank you. $\endgroup$
    – Maurice
    Commented Feb 3 at 21:28

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