2D NMR- Worked Example 1 (COSY)

The first of four worked example problems showing how to tackle a 2D NMR problem. In this video we specifically cover the use of 1D NMR and COSY to differentiate between isomers. We take a deep dive into the 1D NMR splitting, and consider how different motifs can display different J splitting values.
This example was taken from Dr. Chris Schaller's excellent Structure and Reactivity:
employees.csbsj...
And big thanks to CSB SJU Chemistry for reminding me to cite my sources! Check out their channel for more great NMR content:
/ @csbsjuchemistry7378

[@dr.srinivascsir-jrfgatessr3729]

Perfectly explained the concept of COSY. Thank you very much for providing this

[@tyche8800]

This was a really good explanation. I'm surprised it only has 159 likes

[@emmalintelman9852]

Reviewing for an organic final I have and this video was perfect! Thanks:)

[@cleiti1062]

Perfect and so much better than my teacher, thanks!

[@elmiranadirova2737]

Thank you so much, that was really comprehensive

[@nuzamariette7183]

Love you, u are a life saver. Wonderful explanations. Thanks for this video!

[@nurmukhtar1416]

Hi, thank you so much for uploading this. This is very helpful in introducing COSY to students.

[@aakassh35]

Nice explanation mam 🥰

[@baronnavadne8731]

Beautiful voice too

[@aliceqwang731]

this is really helpful. thank you so much

[@matildepereira9849]

Thank you for the explanation!! 😁 Amazing!

[@ganesangobirajeshwaran1752]

Thank you 🍰

[@asifsaleem2290]

2d NMR spectroscopy is very tough course and.....very long,very conceptual 😢

[@taejinkook4290]

Is it ok to have a coupled that 4 bonds away, in the COSY? I'm doing an elucidation and from COSY analysis I saw a coupled between a proton-proton that 4 bonds away: 1st scenario is a meta coupling and one of the meta proton was coupled to the methylene protons that 4 bonds away, And the 2nd scenario is between a symmetrical aromatic proton to and to an olefinic carbon attached to the aromatic carbon.

[@organicwithgrace5388]

It is fine to have 4-bond couplings! They can sometimes be hard to detect. We'd have a hard time seeing something like this on a saturated molecule, because there's too much freedom of rotation. But on a benzene ring like in this example, the rigidity of our system allows us to detect a 4-bond coupling. So the rigidity of your possible molecule is something to consider as you work through your elucidation.

[@taejinkook4290]

@@organicwithgrace5388 thank you for your response. 😊

[@arkamal7551]

Please, can you mention the referance?

[@anisse19v21]

thank you

[@RKYT0]

Why are A and C not connected? their imaginable lines can cross each other? Though it makes sense in the drawn model of the molecule, but when i look at the COSYsignals i can't tell why they should not be connected. Does it have to do with the splitting numbers?

[@organicwithgrace5388]

Our drawn-in guidelines For A and C could cross, but there is no signal where they would cross in our spectrum. Because the protons are so far apart, their coupling is small to non-existant- therefore we don't see the splitting in our 1D spectra (as I talk about at ~23:50), and we don't see it appear in the COSY either. If we took a spectrum of this compound with a very high powered NMR magnet, we might be able to see it in the COSY, and in fact some chemists rely on these longer-distance couplings to confirm a structure! For the purposes of learning COSY, most students aren't required to consider 5-bond proton couplings.

[@RKYT0]

@@organicwithgrace5388 thank you for your fast answer!! But what if you don't have an possible structures of the molecule? I am currently studying on this and need to find out the structure with COSY-NMR. having only the 2D COSY, it seems very hard to me to guess which crossing lines really suggest a real vicinal coupling...

[@maitrachemistry9795]

👍

[@csbsjuchemistry7378]

These problems have been taken from Schaller, Structure and Reactivity. You should cite your sources.

[@nonengkartikarahayu3849]

Jfni fnxi

[@asifsaleem2290]

2d is not explained in detail by you 😘

[@neliniduwari]

Thank you