3
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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.)

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  • 2
    $\begingroup$ 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. $\endgroup$ – orthocresol Oct 23 '15 at 17:05
  • $\begingroup$ OK. So 3 has more priority. $\endgroup$ – Aditya Dev Oct 23 '15 at 17:06
  • 2
    $\begingroup$ Yup it does, which gives you an S configuration, I think. $\endgroup$ – orthocresol Oct 23 '15 at 17:06
  • 4
    $\begingroup$ Also note that the given compound has a second chirality center at the other bridgehead. $\endgroup$ – Loong Oct 23 '15 at 20:04

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