Name: ケム 203有機分光学第14講スピン-スピン結合 (Chem 203. Organic Spectroscopy. Lecture 14. Spin-Spin Coupling)
Uploaded: 2021-01-14T05:22:17.000Z
Duration: 55 min 30 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

>> So when we were talking about coupling constants,

I said sometimes there are some really big differences

between coupling constants, distinct differences

between coupling constant so like an alkanes,

if you have a cis coupling, your J3 H-H is about 10 Hertz,

if you have a trans coupling your J3 H-H that's your three

bond coupling or your vicinal coupling is about 17 Hertz

to make sure you understand the difference between coupling

through a double bond versus coupling between double bonds

so a lot of people particularly when they are starting

out confuse stereochemistry with confirmation.

You can rotate about single bond so even if you have a bond

between two single bonds that might be S-cis

or S-trans that's always a dynamic equilibrium.

It may be heavily weighted toward one way,

but that's not stereochemistry that's confirmation and that

by mind you has a different Karplus curve then the Karplus

curve for an SP2-SP2 carbon pair that's connecting two hydrogens.

So anyway this is specifically not on here but let's now talk

about cyclohexane which is what I'm going to choose for today's,

today's lecture and just remind us of some

of the key features I pointed out, previously we talked

about the Karplus curve for SP3-SP3 systems and we said

that there are some very distinct relationships that are,

so 180 degrees gives you a big coupling constant,

a 60 degree relationship gives you a small coupling constant.

So our axial-axial coupling has a 180 degree dihydro

relationship, those of you who saw the previous sophomore class

that was just filing out got to see Hanna talking

and if you're Newman project you have a 180 degree dihydro angle

and typically you have about 8 to 10 Hertz

If you have an axial equatorial coupling,

these are of course all three bond couplings.

and you remember the Karplus curve that I drew out before

and so that's about 2 to 3 Hertz for each of those.

So what I'm going to do right now is pass out a or,

or mention a very real example that just came up in my lab

and I thought it would make a cool, cool example for spect

and it was a stereochemical problem associated

with the conjugate addition to a, an alpha,

So we were working with nitrocyclohexene,

at the beta position and we were doing an addition of aniline,

I'll write that as pH, NH2 to give the addition product.

and so the issue here was whether we have the

and so of these two stereo-isomers what do we call

the relationship between these stereo isomers?

Diastereomer, so of these two diastereomers each of them

of course is formed as the rasimic and that doesn't matter

because you can't tell one enantiomer from another by NMR,

the spectrum of a racemic mixture is identical

in individual enantiomer unless you have some sort

of chiral solvent or unless I prepare a chiral derivative.

So the only way I could distinguish these two apart

would be say to make an amid the two enantiomers apart would be

to make an amid where I had a chiral acid brought

like a chiral shift reagent or chiral solvating agent.

So the big question is which of these two is formed, the cis,

the cis or the trans and I want to pass out the spectrum,

And I have a few extras here, and some anyone else?

. Alright, great, so we have here the NMR spectrum

and chloroform solution and what I've done here is I've blown

so we call this region the downfield region,

So our molecule of course is night has a fennel group in it

You might notice for example if you look at the fennel group

that we have something that looks like a doublet

There may be some metacoupling going on there, we're not going

to be talking in any great detail about this,

We see something that looks like a triplet,

that's the same integral, if you notice the height

in the integral from here to here is identical

from the height from here to here so that triplet

字幕リスト動画再生

ケム 203有機分光学第14講スピン-スピン結合 (Chem 203. Organic Spectroscopy. Lecture 14. Spin-Spin Coupling)

expect

couple

region

molecule