5.3 Molecules with Multiple Chiral Centers | Enantiomers, Diastereomers, and Meso Compounds | OChem
Chad covers the possible relationships between the different stereoisomers that are possible in structures having multiple chiral centers. He starts by showing how to determine the number of possible stereoisomers based upon the number of chiral centers present. He then shows how to determine when two stereoisomers are enantiomers and when they are diastereomers.
He then introduces Meso compounds, compounds that are achiral even though they have chiral centers. He shows how an internal mirror plane (a sigma plane) is helpful in identifying achiral compounds and can be helpful in identifying Meso compounds as well. Chad concludes the lesson by showing how to identify Meso compounds even when they are drawn in rotational conformations that make it difficult to see the presence of sigma planes.
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00:00 Lesson Introduction
00:56 How to Determine the Number of Stereoisomers
03:44 Enantiomers and Diastereomers when there are Two Chiral Centers
11:05 Introduction to Meso Compounds
18:17 How to Identify Meso Compounds
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This entire ochem series is so incredibly helpful. Thank you!
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Жыл бұрын
Glad to hear it's helping you out Mary!
My OC professor doesn't trust anyone but you. Good job!
@ChadsPrep
24 күн бұрын
Thank you
This video restored my hope in being able to understand stereochemistry. Thank you!
@ChadsPrep
3 жыл бұрын
You're very welcome Tomas! So much vocabulary in the chapter and then there are the ways we recognize the different isomeric relationships all of which can make it very complicated. Glad you found this helpful!
Hi Chad. I dont know how much I should thank to you for making very convincing amazing video. I taught this yesterday at my class. I was so overwhelmed, cuz I got nothing there yet the confusion. But you made me become confident in this section. So thanks to you I might face my exam end of this month with confidence. Hats off for you kind, generous good deed
This is so helful! i couldn't thank you enough. I hope more people find your channel, you are so underrated
@ChadsPrep
3 жыл бұрын
Glad it was helpful, Oshin - thanks for your comment!
don't know what i'd do without you mr. chad !!! seriously, thank you so much.
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10 ай бұрын
You are very welcome.
Another wonderful video! Seriously, thank you so much for all you do, you're actually making these concepts fun to learn!
@ChadsPrep
2 жыл бұрын
Glad to hear it, Jocelyn - Happy Studying!
A perfect explanation! Thank you!
@ChadsPrep
2 жыл бұрын
You're welcome, Verena!
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@ChadsPrep
7 ай бұрын
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Chad. Thank you so much for all you have done! Your videos are of an amazing caliber and you have done an excellent job of helping me with orgo. May God bless you and keep you safe
@ChadsPrep
4 ай бұрын
Thank you for such kind words - He does and hope the same for you!
Thank you for the explanation of "Meso" 👍 Enjoyable learning time 👍
@ChadsPrep
3 ай бұрын
You bet - glad it was!
Thank for taking the time do make this video!!! It helped so much😊
@ChadsPrep
3 ай бұрын
Very welcome!
Thank you for such a good explanation!
@ChadsPrep
8 ай бұрын
You're welcome - Thanks!
I love these incredibly helpful videos... thank you so much Mr. Chad😁😁😍
@ChadsPrep
9 ай бұрын
You're welcome - Glad you do!
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2 жыл бұрын
Glad you finally found us, Ghazal - hope it helps you now. Happy Studying!
Thank you so much!!!
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8 ай бұрын
You are most welcome.
Thank you Chad. I have been struggling by learning with just my professors lectures, and you have changed my life. You definitely accomplished your goal of making orgo chem enjoyable! it feels like a fun game now and just trying to understand its rules. Without you I wouldn't be where I am today. You are amazing!!! you inspire so many students to keep learning !
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4 ай бұрын
Glad the channel is helping!
This was really helpful thanks 😊
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Жыл бұрын
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I am honestly so grateful, I came across your page. I have exams soon and I have now gained the confidence. Thanks a lot!!!
@ChadsPrep
2 ай бұрын
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Hi Chad! Could you please explain why you flipped the molecule at 5:20 (the blue drawing)? Did you flip it, so we can see that they both have wedges (hence their enantiomers)? But the ones on the bottom are diasteriomers as they’re not superimposable images to the molecule? (Ie. they have one wedge and one dash) Thank you so much Chad. I’ve been watching your videos since I was in my first year of undergrad!!! My favourite channel on KZread!
Congrats on 100k
@ChadsPrep
Ай бұрын
Thank you!
Getting A’s because of this invaluable content. Thank you x1000
@ChadsPrep
8 ай бұрын
Great to hear - You're welcome x1000!
thank you man i love you
@ChadsPrep
Жыл бұрын
You're welcome!
Love this guy he’s the only thing getting me through ochem right now 😂
@ChadsPrep
8 ай бұрын
Glad the channel is helping you!
Thanks for this very eductionnal lesson...even if you speak really fast for a non-native speaker...but that's surely the testimony of your passion for chemistry :-) By the way, I like your tee-shirt, you can only be a good man with this 😀
@ChadsPrep
3 ай бұрын
Thank you for your kind words, and if my fast paced passion for chemistry gets too fast, slow down the playback speed under the settings. Happy Studying!
thx
@ChadsPrep
6 ай бұрын
yw
Thx
@ChadsPrep
Жыл бұрын
You bet!
you are the best
@ChadsPrep
Жыл бұрын
Thank you.
Is blue structure of (2R,4S)-2-bromo-4-chloropentane identical to the structure with two hash bonds @ 5:40?
Question for you sir: Imagine if we’d been looking at the mirror image (through the plane of the board) of the very last example (which was (2R,3S)-2-chloro-3-methylhexane just as a reminder). This would render the stereochemistry 2S and 3R. So my question is: do we now list these numerically or alphabetically in the name’s starting parenthetical? (I’m suspecting alphabetical since IUPAC loves the alphabet)
You said diastereomers are those that are not mirror images. Would that include the same molecule with a rotation around one of its bonds for example I think in cis trans diastereomers, there is only rotation and no inversion of configuration? What about the same molecule (no rotation, no inversion). Would that be its own diastereomer? Thank you.
@15:12 isn’t the molecule on lower left side is R and S, when configurations are not matched?
I have a doubt at 15:25 those two compounds are enantiomer even though they have a center of symmetry. Why?
you are >...my whole proffeser
@ChadsPrep
5 ай бұрын
Glad the channel is helping you.
why are the R AND R for bromine and S and S still enantiomers?
Goat
@ChadsPrep
2 ай бұрын
Thank you
Sir, I have a question for meso compounds. Cis-1,4-dichlorocyclohexane is a meso or not? It has two stereocenters in the molecule with a plane of symmetry and its mirror image is superimposable, but it does not have any chiral centers in the molecule. In this case, is it a meso or not?
@reydeleon4091
Жыл бұрын
For your question, it would just be achiral and optically inactive. For a meso compound, there must be both the presence of chiral centers and a plane of symmetry. In this case, there are no chiral centers to begin with so it is just achiral. Hopefully this answer helps.
Hey Chad, I assume when rotating the molecule around to see if it has a plane of symmetry, one shouldn't rotate in a way that changes the configuration right? Like, rotating around a chiral carbon may change the configuration and thus the R:S ratio of 1:1? Or does rotating around a bond typically not affect the configuration?
@ChadsPrep
2 жыл бұрын
Great question Youssef and your intuition at the end was correct! If you're just simply rotating around a bond then it won't change the configuration. Nice!
@MrYahya0101
2 жыл бұрын
@@ChadsPrep Thank you!
@ChadsPrep
2 жыл бұрын
@@MrYahya0101 You're welcome!
***love*** better than like
@ChadsPrep
3 жыл бұрын
Thanks for the comment, Benjamin!
can you explain at 23:33 when you did R&S how you found that, its tripping me up a little, please and thank you
@ChadsPrep
9 ай бұрын
No problem - so at this point we are looking at the left carbon with Br attached we assign priority based on atomic number so Br = 1, the top carbon is number 2 (because it is closer to the next Br atom than the bottom carbon, bottom carbon = 3 and the H = 4 if you trace with your finger or connect with a pen going from 1 -> 2 - > 3 you are moving clockwise or make in a 'right' (R) turn. So its R, the other carbon makes a left turn = S. Hope that helps!
@ChadsPrep
9 ай бұрын
check this video if you need a refresher on assigning R and S kzread.info/dash/bejne/oG2hubiGYLbOhM4.html
@MisterJ34
9 ай бұрын
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@ChadsPrep
9 ай бұрын
@@MisterJ34 Excellent and Kudos!
When you talk about calculating number of stereisomers do you mean number of enantiomers? Because you have got me mixed up.
goat
@ChadsPrep
2 жыл бұрын
Thx!
If you have 3 chiral centers could that still be a meso compound?
@ChadsPrep
2 жыл бұрын
Yes! It has to have at least 2 and the most common examples you're likely to see have 2 chiral centers but the key is that it has to have AT LEAST 2. Hope this helps!
@MrYahya0101
2 жыл бұрын
@@ChadsPrep But if it has 3 then R+S wouldn't be in same ratio, so it would be optically active no? I also wanted to ask you about the cyclohexane you drew. You drew cyclohexane and said that it has plane of symmetry so it has superimposable mirror image. When you draw the mirror image do we consider the configuration of stereocenters to be reversed, eventhough they are not chiral centers? For non-superimposable mirror images, you can just say that the chiral centers were reversed, but superimposable mirror images have no chiral centers, how would you identify them? Thanks.
@ChadsPrep
2 жыл бұрын
You're exactly right Youssef, meso compounds are only possible with an even number of chiral centers. But they can exist with an odd number of stereocenters. Consider 1,2,4-cyclopentanetriol. Carbon atoms 1 and 2 will be chiral centers. Carbon atom 4 will be a stereocenter but not a chiral center (you can't assign it R/S). If carbons 1 and 2 have opposite configurations (one R and one S) it will be a meso compound. My bad but hope this helps!
@ChadsPrep
2 жыл бұрын
When you draw a mirror image the configurations of stereocenters won't necessarily be reversed. I haven't seen this come up before but if I consider the cyclohexane example and other such similar examples the stereocenters aren't reversed in the mirror image. I really want to say that will always be true, but the use of the word ALWAYS is dangerous. But I'm leaning that direction. Hope this helps!
@MrYahya0101
2 жыл бұрын
@@ChadsPrep Thanks Chad! So some molecules will have plane of symmetry and still not be meso compounds (cyclohexane), and some will not have a plane of symmetry (like the one at 18:30) and still be meso compounds? I mean doesn't that just mean we shouldn't use "plane of symmetry" to identify meso compounds?
Would you say your left hand and right butt cheek would be trans? 😅
@ChadsPrep
2 жыл бұрын
😆 😆 😆
Talks too fast😢
@ChadsPrep
Ай бұрын
I get that a lot - you can slow down the playback speed under settings. Happy Studying!