Welcome Guest Search | Active Topics |

Tag as favorite
Altius FL4 Chem/Physics Q3
Nicole_5521
#1 Posted : Wednesday, July 07, 2021 5:04:18 PM
Rank: Advanced Member

Groups: Registered
Joined: 4/30/2020
Posts: 71

Thanks: 0 times
Was thanked: 0 time(s) in 0 post(s)
Hello,

For Q3 on Altius FL4 Chem/Physics, I'm wondering how to realize that Figure 1 is the 6S,7R isomer? From there, how do you realize that it's the top ring (6-membered) that is of interest?

I see how the reaction works from the answer explanation, but I feel like I wouldn't have been able to figure it out by myself. Do you have any tips for solving this type of question? And also solving it fast?

Thanks so much!
INSTR_Molly_129
#2 Posted : Saturday, July 10, 2021 4:41:28 PM
Rank: Advanced Member

Groups: Registered
Joined: 5/23/2021
Posts: 74

Thanks: 0 times
Was thanked: 0 time(s) in 0 post(s)
Hi Nicole,

S/R can definitely be tricky, but I usually do this to help me find a stereocenter. Look for a carbon center with at least three bonds drawn on it. Generally, they have a pretty good chance of being a stereocentre.

As for solving this problem, you will have to look for places that are similar between the reactant and the product. Looking at brevicomin, there is a two carbon chain thats stickng out from a bond to a carbon bound to an oxygen. The only time when we see something like this is on carbon #8 and 9 of the starting epoxide. So, working our way across, we will find that carbon 7 is the first in the ring, and carbon #6 is the next one that would bind to an oxygen (they labelled it carbon #1 to confuse you in the first diagram). This tells me that carbon #6 is therefore the one involved in this ring-closing mechanism.

I hope that helps, please let me know if you have any further questions!

Cheers,

Molly
Nicole_5521
#3 Posted : Saturday, July 10, 2021 5:36:48 PM
Rank: Advanced Member

Groups: Registered
Joined: 4/30/2020
Posts: 71

Thanks: 0 times
Was thanked: 0 time(s) in 0 post(s)
Hi Molly,

How is the 2 carbon chain like carbon 8 and 9?

Thanks
INSTR_Molly_129
#4 Posted : Saturday, July 10, 2021 7:12:40 PM
Rank: Advanced Member

Groups: Registered
Joined: 5/23/2021
Posts: 74

Thanks: 0 times
Was thanked: 0 time(s) in 0 post(s)
Hi Nicole,

When looking at the bicyclic ring structure, the first thing that sticks out to me is the presence of a two-carbon chain on the left of the ring. Those two carbons are then attached to a carbon attached to an oxygen. The only place I see that two-carbon chain is carbon 8 and 9, which is before it hits a carbon with an oxygen attached (carbon #7) in the non-ring, open chain format of the molecule. The other location could have been carbon #1, which is connected to carbon #2 that is connected to oxygen, but that wouldn't make sense... how would I have seen a two-carbon chain sticking out from carbon #2...?

I hope that that is more clear,

Molly

Users browsing this topic
Guest (2)
Tag as favorite
You cannot post new topics in this forum.
You cannot reply to topics in this forum.
You cannot delete your posts in this forum.
You cannot edit your posts in this forum.
You cannot create polls in this forum.
You cannot vote in polls in this forum.

Clean Slate theme by Jaben Cargman (Tiny Gecko)
Powered by YAF | YAF © 2003-2009, Yet Another Forum.NET
This page was generated in 0.098 seconds.