aamc7 chirality question

[muhali3]

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why in the following molecule does C8 have higher priority than C6 when assigning chirality for C7?

http://forums.studentdoctor.net/attachment.php?attachmentid=17493&d=1312402722

An oxygen is two carbons away on both sides. Do ketones have higher priority than epoxides in R/S designation?

 

[tn4596]

c8 have 3 carbons on it
c6 only have 1 carbon.
you dont even need to go to the oxygen to assign priority.

 

[pfaction]

Bumping a year old topic because I got this wrong, albeit due to vision.

So C7, the OH group is obviously #1.
Then, to the left, we have a C, to the right a C.
Further than that, we have a C=O and C-O. The C=O will take precedense.