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In cholesterol, I don't understand why the two points I circled are stereogenic centers. Isn't the left carbon attached to an OH, H, CH2, and CH2? And isn't the right carbon attached to CH, CH2, CH, and H? And according to my understanding, a stereogenic center must be connected to four different groups. I must be doing something wrong here, but I cannot figure out what. Thanks for your help

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    $\begingroup$ In your first example, when you found two CH2 groups you must move to the next carbon to break the tie. In one case you get another CH2 but the other one leads to the carbon of the double bond which is treated as a quaternary carbon C3 is of the S-configuration. Use the same method at the other site. Read about Cahn-Ingold-Prelog rules. $\endgroup$ – user55119 Jul 22 '18 at 1:22
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While we see the strereocenters we just don't see the adjacent carbon but the adjacent group this seeing the adjacent group we can follow that the Marked Carbon is connected by a sp3 and then sp2 carbon from bellow And the Marked Carbon is connected by a sp3 and then also sp3 carbon from above Hope you got it !![enter image description here]1

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  • $\begingroup$ The sp3 arrow should point to the CH2 (C1) to determine C3. It should be compared to the designated sp2 carbon. Follow CIP rules. $\endgroup$ – user55119 Jul 22 '18 at 1:39
  • $\begingroup$ Oh yes I did it by mistake $\endgroup$ – user61535 Jul 22 '18 at 1:55

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