In theprevious post, we talked about theprinciples behind the chemical shift addressing questions like how theppm values are calculated, why they areindependent of the magnetic field strength, and what is the benefit of using a more powerful instrument.

Today, the focus will be on specific regions ofchemical shift characteristic for the mostcommon functional groups in organic chemistry.

Below are the main regions in the¹H NMR spectrum and the ppm values for protons in specific functional groups:

The energy axis is called aδ (delta) axis and the units are given inpart per million (ppm). Most often the signal area for organic compounds ranges from0-12 ppm.

The right side of the spectrum is the low-energy region (upfield) and the left side is the high-energy region (downfield). This might be a confusing terminology andwe talked about its origin earlier, so read that post if you need to know more but you definitely need to remember that:

Downfield means higher energy – left side of the spectrum (higher ppm)

Upfield means lower energy – right side of the spectrum (lower ppm)

Let’s start with the chemical shift of protons of alkyl C-H groups.

The Chemical Shift of Connected tosp³ Hybridized Carbons

We can see in the table thatsp3hybridized C – H bonds in alkanes and cycloalkanes give signal in theupfield region (shielded, low resonance frequency) at the range of1–2 ppm.

The only peak that comes before saturated C-H protons is the signal of the protons oftetramethylsilane, (CH3)₄Si,also calledTMS. This is a standard reference point with the signal set exactly at 0 ppm and you can ignore itwhen analyzing an NMR spectrum. There are a lot of compounds especially organometallics that give signals at negative ppm, but you will probably not need those in undergraduate courses.

One trend to remember here is that protons bonded to more substituted carbon atoms resonate at higher ppm:

The Chemical Shift of Protons Connected to Heteroatoms

The second group of protons giving signal in this region is the ones bonded toheteroatoms such as oxygen and nitrogen. And even though the signal can be in the range from 1-6 ppm, it is usually in thedownfield end of this spectrum.

This is due to thehigher electronegativity of those atomspulling the electron density and deshielding the protons. As a result, they are more exposed to the magnetic field andrequire higher energyradiation for resonance absorption.

The image below can visualize the effect of electron-withdrawing groups on the chemical shift. Suppose the light is the magnetic field, and the triangular object is the electron cloud/density around the given nucleus. The larger the object (the electron cloud) in front of the nucleus, the less it is exposed to the light (magnetic field), thus the smaller the chemical shift. On the contrary, towards the left, we have nuclei that are surrounded by a smaller electron density, and thus the stronger field exposure causes their signal to appear in a higher energy region (downfield):

Once again, recall that the electron density around a nucleus is affected by the electronegativity of the neighboring nucleus.

Thestronger the electron-withdrawing group, the more deshielded the adjacent protons and thehigher their ppm value.

Now, 1-6 ppm for protons on heteroatoms is a broad range and to recognize these peaks easier, keep in mind that they also appearbroader as a result of hydrogen bonding.

The O-H and N-H protons are exchangeable, and this is a handy feature because when in doubt, you can add a drop of deuterated water (D₂O) andmake the signal disappear sincedeuterium does not resonatein the region where protons do:

Other groups that give broad, and sometimes, deuterium-exchangeable signals are the amines, amides, and thiols.

And one more thing, which we will discuss in the signal splitting, is that theOH signal is not split by adjacent protons unless the sample is very well-dried.

The Chemical Shift of Protons onsp² Hybridized Carbons

The protons ofalkenes are deshielded and their signals appear downfield from the saturated C-H protons in the4-6 ppm range.

There aretwo reasons for this. First,sp2 hybridized carobs are more electronegative thansp3 carbons since they have mores character (33% vs 25%s). So,sp² orbitals hold electrons closer to the nucleus than thesp³ orbitals do which meansless shielding, therefore a stronger “feel” of the magnetic field and a higher resonance frequency.

The second reason is a phenomenon calledmagneticanisotropy. When protons on carbon-carbon double bond are placed in a magnetic field, thecirculating π electrons create a local magnetic field that adds to the applied field which causes them to experience astronger net field and therefore resonate at a higher frequency:

This effect is more pronounced inaromatic compounds which have resonance in the range from7 to 8 ppm. The circulation of the p electrons in benzene is called aring currentand the protons experience an additional magnetic field that is induced by this ring current.

Interestingly, aromatic compounds with inner hydrogens such as, for example, porphyrins,[18]-annulene and the ones with hydrogens over the ring are shielded by the induced magnetic field and appearscientifically upfield:

Interestingly,antiaromatic compounds generate a different ring current which in turn generates an induced magnetic field with opposite directions than in aromatic compounds. Thus, antiaromatic systems show the opposite trend: the inner protons appear in a higher ppm area than the outer protons. For example, the protons outside the ring of[12]annulene appear at 5.91 ppm whereas the inner protons are characterized by a chemical shift of 7.86 ppm:

The Chemical Shift of Alkynes

The p electrons of a triple bond generate a local magnetic field just as we discussed for alkenes and one would expect to see their signal more downfield since thesp carbon is more electronegative thansp² carbons.

However, hydrogens of external alkynes resonate at a lower frequency than vinylic hydrogens that appear in the 2-3 ppm range.

The reason is that, unlike alkenes, the induced magnetic field of the p electrons in the triple bond isopposite to the applied magnetic field. This puts the proton in a shielded environment and thus it feels a weaker magnetic field:

The conflicting effects ofmagnetic anisotropy and the higher electronegativity ofsp hybridized carbons put the signal of acetylenic hydrogens in between alkanes (1-1.8 ppm) and alkenes (4-6 ppm).

Check Also

• NMR spectroscopy – An Easy Introduction
• NMR Chemical Shift
• NMR Chemical Shift Range and Value Table
• NMR Number of Signals and Equivalent Protons
• Homotopic Enantiotopic Diastereotopic and Heterotopic
• Homotopic Enantiotopic Diastereotopic Practice Problems
• Integration in NMR Spectroscopy
• Splitting and Multiplicity (N+1 rule) in NMR Spectroscopy
• NMR Signal Splitting N+1 Rule Multiplicity Practice Problems
• ¹³C NMR NMR
• DEPT NMR: Signals and Problem Solving
• NMR Spectroscopy-Carbon-Dept-IR Practice Problems

14 thoughts on “NMR Chemical Shift Values Table”

1. Is there any information on multiple splitting patterns, e.g. doublet of doublet or doublet of triplets, for example?

   Reply

   • Although I have not written an article on complex splitting yet, they are summarized in the NMR study guides on page 3. You can download them on theCS Benefits page.

     For the general splitting patterns, refer to these:
     Splitting and Multiplicity (N+1 rule) in NMR Spectroscopy
     NMR Signal Splitting N+1 Rule Multiplicity Practice Problems

     Reply

2. Thank you! I was so confused about the energy of upfield and downfield…

   Reply

   • Good to know it makes more sense now, Raul.

     Reply

3. Very nice and easy to understand.
   Thank you very much

   Reply

   • Thank you, Zia.

     Reply

4. Hello,
   How would I sketch the H NMR spectrum of 4-chlorocumene?

   Reply

   • Hi,

     ChemDraw is the gold standard for organic chemistry. It is a paid program, however, they have the possibility of free use in the browser –https://chemdrawdirect.perkinelmer.cloud/js/sample/index.html. I don’t know if this option comes with sketching spectra though. You can try ChemSpider too.

     Reply

5. My heartiest thanks.

   Reply

6. This is a really nice resource! Thank you!

   Reply

7. Nice thanks

   Reply

8. Very useful info
   Thank you for sharing.

   Reply

9. Wow what a well detailed explanation
   It took me only ten minutes to understand thank you

   Reply

   • Thank you, Evelyn. Great to hear the aim of making things easy to understand is working!

     Reply