Welcome Guest Search | Active Topics |

Tag as favorite
CIS/TRANS
Josh_4080
#1 Posted : Thursday, June 11, 2020 6:09:45 PM
Rank: Advanced Member

Groups: Registered
Joined: 3/18/2019
Posts: 30

Thanks: 0 times
Was thanked: 0 time(s) in 0 post(s)
Just a quick question: I don't really understand when CIS/TRANS is going to be more/less stable? Is CIS always less stable because of steric interactions? I remember some molecules are actually stabilized by things like hydrogen bonds through steric interactions (like the one we saw yesterday in the AAMC practice). So I was just wondering if anyone has a system to determine stability in CIS/TRANS isomerism.

Thanks!
INSTR_Katerina_102
#2 Posted : Saturday, June 13, 2020 12:22:04 AM
Rank: Advanced Member

Groups: Registered
Joined: 6/24/2019
Posts: 250

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

Good question - I would say pretty much 99% of the time (probably closer to 100% of the time for MCAT Chem) the trans diastereomer is more stable because of sterics.

It is true that H bonding can change things, but this stabilization tends to be only really significant in 5 member rings or 6 member rings (with a few exception for fused ring systems).

If this is going to switch cis/trans stability, they would heavily imply it in the question as it's a bit more of an advanced topic (recall that they stated stabilities for the 7 member ring H bond case and had you rationalize based on information given).

For your base knowledge, unless you're asked to do something otherwise, keep it simple and assume that CIS is higher energy than TRANS due to sterics.
Users browsing this topic
Guest
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 0.079 seconds.