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Topic: [Solved] Cahn-Ingold-Prelog ACS Question on YouTube  (Read 1559 times)

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Offline benz0icacid

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[Solved] Cahn-Ingold-Prelog ACS Question on YouTube
« on: May 18, 2024, 02:12:36 PM »
Hello!
I'm watching an ACS Ochem 2 Exam Review: https://www.youtube.com/watch?v=OQctLH-psYc&list=PL3A1cf8LCsnlSRO3HEygntDa4cd9tQh2U&index=1

At timestamp 4:30, we are assigning R and S configuration for the epoxide's carbon #3. We are comparing the carbon with O, C, H, and the carbon connected to Br, H, H. The carbon connected to OCH is given 2nd priority, and the carbon with BHH is given 3rd priority. Why is that? I thought since Br has the higher mass, it would have 2nd priority?

I also found a similar question on R/MCAT: https://www.reddit.com/r/Mcat/comments/91mzf1/br_or_oh_higher_priority/

I would appreciate the clarification. Thank you for your time and patience!
« Last Edit: May 18, 2024, 03:45:36 PM by benz0icacid »

Offline Babcock_Hall

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Re: Cahn-Ingold-Prelog ACS Question on YouTube
« Reply #1 on: May 18, 2024, 03:07:26 PM »
The video looks incorrect to me.

Online Hunter2

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Re: Cahn-Ingold-Prelog ACS Question on YouTube
« Reply #2 on: May 18, 2024, 03:43:44 PM »
It should be the cis - 4-bromo-2R,3R epoxy- butan-1-ol.

Offline benz0icacid

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Re: Cahn-Ingold-Prelog ACS Question on YouTube
« Reply #3 on: May 18, 2024, 03:44:04 PM »
I agree. Also, it doesn't make sense for it to be 2R, 3S and it's cis. It would be 2R, 3R, if I'm not mistaken.
Thanks!
edit: exactly, @Hunter2. Thank you!

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