January 17, 2022, 09:21:52 PM
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Topic: Is this molecule chiral or achiral?  (Read 1006 times)

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Offline rolnor

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Re: Is this molecule chiral or achiral?
« Reply #15 on: December 02, 2021, 05:19:14 PM »
You need a rotational barrier of 23kcal/mol to see this type if chirality. Its easy to calculate the rotational barrier with molecular mechanichs software.
https://en.m.wikipedia.org/wiki/Chirality_(chemistry)

Offline mjc123

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Re: Is this molecule chiral or achiral?
« Reply #16 on: December 03, 2021, 10:17:31 AM »
Quote
@Babcock_Hall I'm not saying the information isn't useful, it's just I don't understand it well enough to get any use out of it, I'd rather he actually explained it rather than answering my question with a question.

I'm sorry if you didn't find my response helpful, but that's the kind of forum this is. We don't simply give people answers, but try to help them learn by giving them pointers to help them work it out for themselves. Like you, I am bound by the forum rules (please read them if you haven't already), so I can't just tell you the answer (especially if, as some people think, it's the wrong answer!). There are other forums that will do that if that's what you want.

Of course this depends both on where you are in your learning and my ability to explain at the right technical level, so it doesn't always succeed, but we are trying to do something more constructive than simply spoonfeed answers.

Offline bigfranz1

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Re: Is this molecule chiral or achiral?
« Reply #17 on: December 03, 2021, 11:14:10 AM »
@Babcock_Hall I think maybe you underestimate my chemistry ability, in order to get into uni to do this course I did a course that was mostly biology and physics and only a bit of chemistry (only spend 1 term doing organic chem), it wasn't anywhere near in depth as what I'm learning now. I feel like I made an attempt and gave my reasoning, but I seriously don't know how to answer his question. Those papers that were linked still don't really help me too much and I don't have the time to read it, understand it and make notes as I have other modules to do work in too. It's not like the things I'm learning about are completely alien to me, and I can get a grip on most of it, it's just as I mentioned my lecturers explain it in a very simple way with piss easy examples and from what I learn from them and some independent learning I can't find a way to apply it.

Offline Babcock_Hall

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Re: Is this molecule chiral or achiral?
« Reply #18 on: December 03, 2021, 02:06:12 PM »
I hope that you learned one thing, that a molecule does not need a center of chirality to be chiral.  I would hope that you learned at least that the size of the rotational barrier is the key question.  I suspect that Rolnor is correct concerning your molecule.

Offline kriggy

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Re: Is this molecule chiral or achiral?
« Reply #19 on: December 06, 2021, 04:59:41 AM »
The issue witht your  molecule is quite complicated. I did my PhD with atropoisomeric compounds and there are some good answers already in this thread.

The link to the princeton lab looks very usefull esp. page 9.

I suppose (as was already mentioned) at low temperature, you might be able to separate the enantiomers by suitable method. You have ortho-ortho  monosubstituted biphenyl, thats not exactly stable with regards to the bond rotation but I think it could be done and be observed in some kind of LC separation.

I dont think you can separate the enantiomers and keep like one vial with P and one vial with M enantiomer, they are going to racemize quickly.

a) does the molecule have non-superimposable mirror images?
b) are the enantiomers stable?
c) Can we call it chiral if it only exists as a racemic mixture?

Those are probably the questions you are suppose to ask and answer for your homework assignment.

Offline rolnor

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Re: Is this molecule chiral or achiral?
« Reply #20 on: December 06, 2021, 12:23:00 PM »
There is an name for chiral compounds that have fast interconversion of the enantiomers, I dont remember the name? Amines with 3unique substituents on nitrogen belongs to this class I believe.

Offline Borek

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Re: Is this molecule chiral or achiral?
« Reply #21 on: December 06, 2021, 06:03:51 PM »
There is an name for chiral compounds that have fast interconversion of the enantiomers, I dont remember the name? Amines with 3unique substituents on nitrogen belongs to this class I believe.

No idea about the name, but the process they undergo is called https://en.wikipedia.org/wiki/Pyramidal_inversion
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