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In bicyclo[2.2.1]heptan-2-one, arrange the numbered groups according to CIP rules:

bicyclo[2.2.1]heptan-2-one

Group 1 will have highest priority because oxygen atom is attached to 1. (It can be considered as two oxygen atoms).

Group 4 will have least priority due to least atomic number among the numbered groups.

But I am confused about order of priority of group 2 and 3. Both have same atoms. (So I will check the next atom which is also same.)

Gaurang Tandon
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Aditya Dev
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    Group 2 has -CH2-C(CHH); group 3 has -CH2-C(CCH) where (XYZ) means that the carbon is bonded to XYZ atoms. I mean, you already used this rule to determine that 1 was the highest, didn't you. 1 is -C(OOC) whereas 2 and 3 are both -C(CHH). Since O > C in atomic number 1 > 2,3. Same goes for 2 and 3 you just need to go one carbon further. – orthocresol Oct 23 '15 at 17:05
  • OK. So 3 has more priority. – Aditya Dev Oct 23 '15 at 17:06
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    Yup it does, which gives you an S configuration, I think. – orthocresol Oct 23 '15 at 17:06
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    Also note that the given compound has a second chirality center at the other bridgehead. –  Oct 23 '15 at 20:04
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    @orthocresol: It's an S-configuration if the methylene 3 is above the plane of the 6-membered ring. I presume that your "I think" considers this point. – user55119 Sep 18 '20 at 20:29
  • @user55119 yes, an important point. I must admit, I have no recollection of what I was thinking at that time. :-) – orthocresol Sep 18 '20 at 20:35

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