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Proton NMR question

Pleeease can someone help me to understand the proton (H) NMR below - what causes the peak furthest to the left?

The areas of the peaks are 2, 3 and 3.

So far I've worked out that:

•

The second peak (7.5 ppm) corresponds to the 5 H on the aromatic ring (there are 2 pairs of equivalent H nuclei in the ring).

•

The last peak is from the 3 equivalent H nuclei in the CH₃

So doesn't that cover all 8 hydrogens in the molecule? What does the first peak come from? :s-smilie:

EDIT: Actually I think I get it now (maybe)... are first 2 peaks both from the H nuclei in the ring?

(edited 9 years ago)

Reply 1

Black Flame

Hey, I'm not sure but I think u are wrong 'bout the 3rd peak. It's a singlet so it must be on his own with no surrounding H. I think the highest peak corresponds to the 3 Hs on the CH3. the peak is showing the type of H and the splitting shows how many H are around that hydrogen. So do not expect to see a triplet to mark the Hs in CH3. Hope I helped. Like I said I'm not fully sure so better check.

Black Flame

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Reply 2

charco

Study Forum Helper

Original post by tingirl

Pleeease can someone help me to understand the proton (H) NMR below - what causes the peak furthest to the left?

The areas of the peaks are 2, 3 and 3.

So far I've worked out that:

•

The second peak (7.5 ppm) corresponds to the 5 H on the aromatic ring (there are 2 pairs of equivalent H nuclei in the ring).

•

The last peak is from the 3 equivalent H nuclei in the CH₃

So doesn't that cover all 8 hydrogens in the molecule? What does the first peak come from? :s-smilie:

EDIT: Actually I think I get it now (maybe)... are first 2 peaks both from the H nuclei in the ring?

Yes the peaks downfield are due to the protons in the ring.

Reply 3

username913907

Original post by tingirl

Pleeease can someone help me to understand the proton (H) NMR below - what causes the peak furthest to the left?

The areas of the peaks are 2, 3 and 3.

So far I've worked out that:

•

The second peak (7.5 ppm) corresponds to the 5 H on the aromatic ring (there are 2 pairs of equivalent H nuclei in the ring).

•

The last peak is from the 3 equivalent H nuclei in the CH₃

So doesn't that cover all 8 hydrogens in the molecule? What does the first peak come from? :s-smilie:

EDIT: Actually I think I get it now (maybe)... are first 2 peaks both from the H nuclei in the ring?

Splitting goes nuts on Phenyl rings so don't warry about trying to interpret the splitting pattern. The higher shift peaks will correspond to the meta protons and low shift the ortho and para

Reply 4

tingirl

Original post by charco

Yes the peaks downfield are due to the protons in the ring.

Original post by JMaydom

Splitting goes nuts on Phenyl rings so don't warry about trying to interpret the splitting pattern. The higher shift peaks will correspond to the meta protons and low shift the ortho and para

Thanks guys! :smile:

Reply 5

BJack

Original post by tingirl

The areas of the peaks are 2, 3 and 3.

•

The second peak (7.5 ppm) corresponds to the 5 H on the aromatic ring (there are 2 pairs of equivalent H nuclei in the ring).

The equivalent nuclei will all contribute to the peak integral, which seems to be where your counting went wrong.

Reply 6

Infraspecies

Aromatic splitting patterns are a mess of crap, don't try to interpret them if they're like that. It's a waste of time.

There, there'll be strong coupling and magnetic inequivalence to deal with. You won't know what those are, but they're reasons why you shouldn't even bother trying.
They're around 8 ppm, they integrate to the correct number, hence they're aromatic, jobs a good'n.