Q4. Diethyl ether has two signals in its 1H NMR and 13C...

Q4. Diethyl ether has two signals in its 1H NMR and 13C spectra. Indicate whether the methyl or methylene protons will resonate at a higher chemical shift. Briefly explain. Q5. How many signals does isopropanol have in its 1H and 13C NMR spectra? Predict the chemical shifts for the 1H signals. Q6. Label the equivalent protons in each of the compounds below Ha, Hb, etc. Rank the protons based on their chemical shift, where 1 = highest chemical shift.

Transcript

00:01 In this problem, we're first going to look at die -either, so that's this here.

00:06 And we're asked if these hydrogen and carbons or if these ones will be shifted further down the field, so which will have a higher chemical shift.

00:18 So here, you're next to this highly electronative atom oxygen.

00:23 So oxygen is going to pull electron density towards it, and that does what we call deshielding.

00:30 So there's not as much to shield this carbon and hydrogens.

00:34 So they end up getting a greater chemical shift or being further downfield than our ones here, because electron density is being pulled away from these carbons.

00:48 So our ones in red will have the highest chemical shift.

00:54 Then we look at exopropanol, and we want to know how many signals it has.

00:59 So we have these two c .h3 groups.

01:04 And if you look at these ch3 groups, they're both attached the same carbon, and they're both equally far away from our oxygen.

01:12 So they're actually going to show up.

01:13 The carbons and hydrogens will show up as the same peak.

01:17 So this will be one peak for each.

01:20 Then there's a carbon here, and there's also another hydrogen.

01:24 So this carbon will show up as its own peak.

01:28 So that's a second carbon peak, and this hydrogen will show up by itself, so that's a second hydrogen peak.

01:36 And this hydrogen on the alcohol will have a different proton shift as well.

01:41 So we're going to have three peaks or signals for hydrogen nmr.

01:47 And we're going to have two peaks or signals for carbon 13 nmr.

01:55 Then we're looking at these four structures at the bottom.

02:00 And we're labeling equivalent protons, but we're also going to rank the protons based on chemical shift.

02:07 So first, let's look at this one here.

02:12 So you'll notice the plane of symmetry going down this.

02:16 So our hydrogens on either side of it will have the same shift.

02:19 So if we call these all ha, these will have the same chemical shift.

02:24 And then we'll call these hb down here.

02:27 They'll have a different shift.

02:29 And because our ha hydrogens are next to this chlorine that's going to pool electron density towards itself and deshield them, these hydrogens will be the furthest downfield or have the highest chemical shift, whereas these won't be quite as deshielded...

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