Talk:Nuclear magnetic resonance spectroscopy

From Wikipedia, the free encyclopedia
Jump to: navigation, search
          This article is of interest to the following WikiProjects:
WikiProject Physics (Rated B-class, High-importance)
WikiProject icon This article is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
B-Class article B  This article has been rated as B-Class on the project's quality scale.
 High  This article has been rated as High-importance on the project's importance scale.
 
WikiProject Chemistry (Rated B-class, High-importance)
WikiProject icon This article is within the scope of WikiProject Chemistry, a collaborative effort to improve the coverage of chemistry on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
B-Class article B  This article has been rated as B-Class on the project's quality scale.
 High  This article has been rated as High-importance on the project's importance scale.
 
WikiProject Molecular and Cellular Biology (Rated B-class, High-importance)
WikiProject icon This article is within the scope of the WikiProject Molecular and Cellular Biology. To participate, visit the WikiProject for more information.
B-Class article B  This article has been rated as B-Class on the project's quality scale.
 High  This article has been rated as High-importance on the project's importance scale.
 
WikiProject Spectroscopy (Rated B-class, High-importance)
WikiProject icon This article is within the scope of WikiProject Spectroscopy, a collaborative effort to improve the coverage of Spectroscopy on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
B-Class article B  This article has been rated as B-Class on the project's quality scale.
 High  This article has been rated as High-importance on the project's importance scale.
 
WikiProject Citizendium Porting (Last updated: Never)
WikiProject icon This article is within the scope of WikiProject Citizendium Porting, a collaborative effort to improve Wikipedia articles by working in any useful content from their Citizendium counterparts. If you would like to participate, you can visit the project page, where you can join the project and see a list of open tasks.
 
Note icon
This article is out of date with its Citizendium counterpart and needs to be updated.
Current with its Citizendium counterpart article as of: Never

Image Removal[edit]

I removed this image because there's some unsafe lab practice in the picture and wikipedia should not be encouraging bad safety. User should be wearing gloves while handling unlabeled compound in a marginally sealed tube. --Takometer 01:58, 23 April 2006 (UTC)

It's not unlabelled. Look at the top. Safe lab practice doesn't demand you to wear gloves regardless of what you are doing. In this case it was a harmless protein sample in water. I put the picture back in, since I think it adds to the information content of the article. Kjaergaard 02:09, 23 April 2006 (UTC)
Usually I'd agree with Takometer that chem photos should be seen to be safe, but I think it's appropriate in this case not to have gloves. In fact, gloves are usually discouraged with NMR tubes as they can lead to contamination of the probe. Walkerma 04:25, 23 April 2006 (UTC)

History[edit]

Page moved from NMR_Spectroscopy (now a redirect). Lee-Jon 09:28, 19 May 2005 (UTC).

Added spin-spin (scalar) coupling section. Lee-Jon 10:45, 19 May 2005 (UTC)

Correlation Table[edit]

This article could do with a good correlation table for 1H and 13C since the're the most used, just having one of those littl graphs with chemical shift on the x axis and a picture of propane around 1ppm can be really helpful —Preceding unsigned comment added by 129.11.251.229 (talk) 15:47, 25 February 2009 (UTC)

Work in Progress![edit]

Hello all! This page has been created at a request on the NMR discussion board. The idea for this page is to give a simple introduction into NMR_Spectroscopy without the need for theory. The knowledge typically required of a graduate student to understand his NMR spectra!

It has been written in a basic style and contains simple examples. I ask people who'd like to edit in more detail/or more complex terms, to refer and preferably reference to the Nuclear_magnetic_resonance page. Lee-Jon 10:45, 19 May 2005 (UTC)

Are you finished?[edit]

User:Lee-Jon, are you finished with this NMR Spectroscopy article? If you are, I might make more edits to it. If not, I would rather wait until you are finished. H Padleckas 19:33, 23 May 2005 (UTC)

Hi![edit]

I'm still working on some sections. I'll post when I'm done. What were you thinking of adding? -Lee-Jon

I have just written an article discussing tetramethylsilane, often called TMS. H Padleckas 07:36, 27 May 2005 (UTC)

Protein NMR[edit]

I added a section a section on protein NMR, even though I'm not sure it fits very well with the rest. Eventually it is going to get it's own page.... Kjaergaard 06:40, 3 January 2006 (UTC)

Peak sizes in split peaks, style[edit]

I just noticed this phrase in the section on multiplicity: "The ratio of height between them is 1:2:1." Shouldn't that be the ratio of areas? With the doublet it uses the word area, though for quartets it says "intensity" which seems rather vague to me. Isn't the word area or areas the correct term here? Walkerma 05:37, 3 February 2006 (UTC)

By first principles, area would be right--"intensity" as "strength of signal" where the "signal" is the whole peak. By practical experience, height is not reliable. OTOH, I've seen it taught as height because it's aproximately proportional to area for reasonably isolated signals in simple compounds (i.e., classroom examples). Integration curves are often hard to read for the level of accuracy needed to see the ratios and the various peaks of a multiplets often overlap. In fact, the deviation from a symmetric height ratio at one chemical shift is taught as a way to figure out what other chemical shift might be coupled to it. DMacks 06:01, 3 February 2006 (UTC)

Also, I notice that the style in this section is more like that of a tutoring session than an encyclopedia, complete with questions like "So do we get four peaks?" The content looks good (other than the area/height problem), but shouldn't it be more encyclopedic? I'll await comments before making any changes. Walkerma 05:37, 3 February 2006 (UTC)

examples[edit]

It would be nice to see some picture examples of NMR spectra, as by reading the article, it is hard to get a grasp of what the specta look like Jhum101 06:11, 25 February 2006 (UTC)

Not the most common of molecules but see:
  • Carbene 13C NMR.png
Also found on commons:
  • Menthol Proton Spectrum.jpg
  • Widmo1HNMR.png

-Quantockgoblin (talk) 02:23, 23 March 2008 (UTC)

Agreed! Of these pictures, I think the last one is the clearest. Akita86 (talk) 22:32, 28 October 2009 (UTC)

Ethanol Spectum?[edit]

Does anyone have an ethanol NMR spectrum similar to the one described in the article? Since interpreting NMR spectra for structure determination is a very visual process, it might be useful to have a graphic to go along with the description of chemical shift, integration, and spin-spin coupling in order to make it more clear. Ghiles 11:30, 16 May 2006 (UTC) It should be fairly easy to make a sketch of one, that outlines the main features... I'll look at it when I have time.... Kjaergaard 16:10, 16 May 2006 (UTC) http://mmcd.nmrfam.wisc.edu/expnmr/expnmr_00299.html —Preceding unsigned comment added by 75.72.165.97 (talk) 14:22, 5 February 2009 (UTC)

Since the H-1 NMR spectrum of ethanol is discussed in the article, in particular the "Chemical shift" and the "J-Coupling" sections, in the "J-Coupling" section I added a diagram of a 1-dimensional H-1 NMR spectrum of ethanol I found in WikiCommons. It seems to be a theoretically-calculated or computer-generated picture turned into a *.gif file instead of a picture of an experimentally obtained spectrum. Few NMR spectra are available in Wikimedia, as far as I can tell. Images of NMR spectra of vanillin previously present in some NMR articles were removed because they did not have a free license. I believe most experimental NMR spectra images present on the internet are not freely licensed. I am now looking for C-13 NMR spectra images, not necessarily ethanol, for the C-13 NMR article. H Padleckas (talk) 03:33, 25 January 2012 (UTC)
The diagram of 1-dimensional H-1 NMR spectrum provided by H Padleckas above is not correct and should be replaced. The chemical shift of the CH2 group is not 4 and that of OH group in ethanol is not 2-3 as mentioned in the article. In fact, these should be interchanged. The CH2 has a chemical shift of 2-3 and the OH has a chemical shift of about 4. This can be verified by referring to any standard text book on Physical Chemistry or NMR spectra (For example, (1)Peter Atkins and Julio de Paula, "Atkin's Physical Chemistry" 7th edition, Oxford University Press, 2002, page 587 (2)Peter Atkins and Julio de Paula, "Atkin's Physical Chemistry" 8th edition, Oxford University Press, 2006, page 520 (3)Mark Ladd, "Introduction to Physical Chemistry", 3rd edition, Cambridge University Press, 1999, page 134). I have already made this correction in the text of the article as a minor edit, but now the figure of ethanol spectrum has to be changed to reflect this correction. An NMR spectrum of ethanol is available in almost any text book of spectroscopy. — Preceding unsigned comment added by Ravidivakaran (talkcontribs) 16:56, 23 January 2014 (UTC)
No, the spectrum of ethanol has to be the spectrum of ethanol, you cannot change it to match a theory (physical chemistry texts often have special cases or diagram styles compared to what is standardly done for NMR spectroscopy). Splitting and integration both contradict your claim of the smaller singlet at ~2.5 ppm being the one OH atom (compared to the two CH2 atoms with >2 neighbors). I just checked McMurry's Organic Chemistry, which has a correlation table with OH as 2.5–5.0 ppm and alcohol/ether CH at 3.3–4.5 ppm. It has a spectrum of 1-propanol that it assigns the OH as a singlet with area 1.00 at 3.17 ppm and the CH2 as a triplet with area of 2.00 at 3.58 ppm (notice the greater shift of CH, and the splitting correlated with the number of CH neighbors, as for the ethanol in our article). Here is an actual ethanol spectrum that again agrees[1].
I don't have my Atkins text handy, but I see ones agreeing with our ethanol all over the web, and also I don't see any correlation tables that are more in agreement with your reversed assignment of an OH being more shifted than the H on its C (see for example [2]). I would be surprised if they make such a glaring mis-assignment without explaining something very nonstandard about the spectral analysis they are doing. DMacks (talk) 17:22, 23 January 2014 (UTC)

Virtual Coupling[edit]

Can anyone explain virtual coupling? I am unclear as to the term and I think a good explanation would be useful. Not sure if it should be its own topic or under NMR spectroscopy. Nothing found through a wiki search. M_Stone 16:51, 12 June 2006

I'm not sure that would be appropriate for a general article on interpreting NMR, but perhaps in an article on interpreting couplings in an NMR spectrum which certainly is a topic that might deserve its own article. Maybe I'll gather some source material together and try to write one up soon. Ghiles 10:16, 16 June 2006 (UTC)
I agree. Good Idea. M_Stone 17:42, 16 June 2006

Redirects from other articles[edit]

I think that MRS is another generally accepted common term for NMR spectroscopy. Thus, the MRS disambiguation page should have a reference to this page. Also, "Magnetic Resonance Spectroscopy" redirects to the MRI page even though it should redirect here. Also, the MRS section of the MRI should have a link to here because this is really the main article to the small description over there.

Chemical shift[edit]

Can someone explain the chemical shifts in molecules like flouroethane,chloroethane,bromoethane....???

Deuterated solvents list[edit]

I wonder if we really need the list, bearing in mind that CDCl3 is just a stub, while the other articles are redlinked. The bulk properties are not very much different than the undeuterated form, and probably will only remain a stub permanently. There are also important solvents not listed such as DMSO-d6 and D2O. --Rifleman 82 15:00, 1 February 2007 (UTC)

Hmm .. right. Err .. what about a document 'deuterated solvents', that describes how they are made, that their properties are closely related to the un-deuterated solvents, something about specific toxicity and some special properties (I think there are cases of odd effects on boiling points). And then create a redirect from the common deuterated NMR-solvents to these articles? --Dirk Beetstra T C 15:10, 1 February 2007 (UTC)
No objections, though I won't be able to contribute much to this article. I assume this would be a logical daughter article of Nuclear Magnetic Resonance, similar to NMR tube? --Rifleman 82 16:25, 1 February 2007 (UTC)
I have begun this page very roughly on my profile page. It is my first major bit of editing so I'm not sure about formatting and some guidelines - thus I wanted to garner some comments before proceeding. I have headings for some key points which I think gives enough justification for setting this up as a new page. At the moment there are only some bare bones however - and no references yet I'm afraid!--WhirlwindChemist (talk) 22:45, 28 August 2008 (UTC)
That looks like a nice start, and the formatting is pretty good! I'd suggest using {{List of NMR solvents}} in place of your list - I took the liberty of editing your page to reflect that. By the way, for this sort of work I'd recommend using a sandbox page like User:WhirlwindChemist/Sandbox - you can feel free to create pages like that for preparing new articles or rewrites. Thanks, Walkerma (talk) 00:14, 29 August 2008 (UTC)
Thanks for the feedback and help Walkerma - I have yet to learn how to do everything properly, but at the same time knew that if I didn't start somewhere I would never learn by just reading through all the guidelines etc. Back to business though: I have created User:WhirlwindChemist/Sandbox as you suggested, and your modification is very welcome! If only I had thought about that I would have saved time typing out and formatting a list of all those deutero-solvents! --WhirlwindChemist (talk) 01:12, 29 August 2008 (UTC)
This is the only way to learn, to BE BOLD, jump in and try things. That's the beauty of Wikipedia - if you mess up, people can always fix things or revert your mistakes. And you'll find that the chemists are a pretty friendly bunch. Be sure to drop by at WP:Chemistry and let us know when you have the article done. Another useful thing if you find a feature on a page that you like, you can copy the code over. Feel free to ask me questions, Walkerma (talk) 02:13, 29 August 2008 (UTC)

NMR Data Processing[edit]

I have proposed that the NMR Data Processing page is being merged into this page. I don't know if there is anything worth salvaging over there, but the page doesn't make much sense by it self.... Kjaergaard 21:58, 13 February 2007 (UTC)

It would be nice if we had a separate article on this rather technical aspect - there is a whole world of information on that side of NMR that deserves an article. However, the content over there right now isn't necessarily that helpful. Walkerma 04:20, 28 May 2007 (UTC)
Reject. Spectroscopic applications are separate from data processing. Mattabat 08:39, 2 June 2007 (UTC)
Agree with above comments and removed merge with incoherent Data Processing article 84.92.241.186 21:48, 6 June 2007 (UTC)

Basic techniques para[edit]

I propose clearer wording, along these lines:

Delete: "The energy of the absorption and the intensity of the signal are proportional to the strength of the magnetic field."

Insert: "For a particular sample, the resonant frequency, resolution, and signal-to-noise ratio of an instrument are proportional to the strength of the magnetic field. Furthermore, a larger sample improves signal-to-noise ratio, and a more uniform field improves resolution."

Or something like that. Any suggestions? GilesW 20:07, 22 August 2007 (UTC)

Determining the spin system?[edit]

I am having trouble determining the spin system of molecules (ie. A2X2, AMX, etc..). I can see how protons are chemically equivalent but I am not completely grasping what makes them magnetically different. Would someone be willing to go into more detail about this? Or at least post some links? I have a set of molecules (practice problems) for which I eventually have to predict a spectra, but am reluctant to move forward until I know the spin systems are correct. -L 76.123.153.39 19:58, 30 October 2007 (UTC)

Spectrometer[edit]

Should there be some kind of general description of the actual machine that conducts NMR spectroscopy? Perhaps a diagram of the machine? Or should that be made for a new article. LostLucidity (talk) 22:55, 24 January 2008 (UTC)

I think I'm also looking for this. I came in looking to understand the term "NMR spinner", which I think is part of a typical instrument, and haven't won yet. ArthurDent006.5 (talk) 12:11, 28 July 2013 (UTC)

iNMR[edit]

hi everyone. I think one should add iNMR hence it's the only programm for Mac OS X. It's page is www.inmr.net.

thanks alot!

Max —Preceding unsigned comment added by 84.176.197.103 (talk) 15:30, 4 February 2008 (UTC)

Request for additional sections[edit]

After reading this page, I still was not clear how NMR spec works. Nuclei absorb energy, and then what? How is the signal measured and processed? A diagram of the structure of an NMR spectrometer would help.

Also, the article would benefit from the addition of a History section. Who invented NMR spec? How has it evolved? What is the state of the art? What are some important discoveries that it has led to? —Preceding unsigned comment added by 65.199.186.2 (talk) 22:57, 14 January 2011 (UTC)

chemical shift picture[edit]

Readded chemical shift picture. There is not existing illustration which shows a chemical shift. Since another editor added it, the (tenuous) consensus is that it belongs in the article. Gerardw (talk)

It's not an informative addition though. This image belongs at hexaborane.
I'll run an NMR spectrum of something simple tomorrow. Acetone only has one line (one chemical shift, all protons equivalent, δ ≈ 2.16 ppm) so doesn't illustrate the concept of different protons having different chemical shifts. Ethanol has three proton environments but is complicated by (i) J-coupling and (ii) hydrogen bonding and proton exchange - OH line may not appear or may be very broad.
If anyone has any suggestions for a molecule with several different chemical shifts but no J-coupling or other complexities, I'll see if I can obtain its NMR spectrum.
Cheers,
Ben (talk) 23:06, 6 March 2011 (UTC)
I agree that the borane case is a pretty poor example for this page...overly complex and poorly resolved. Heck, even the interpretation is confusingly written (diagram not labeled for which H are which signal, etc.) t-Butyl acetate, t-butyl methyl ketone, methyl pivalate, and pivaldehyde are common teaching examples of 1H-NMR structure/shift effects that do not have any splitting or exchange-broadening effects. Shame they only have two signals each though. Methyl acetoacetate or a 1,3,5-trisubstituted benzene with some combination of methyl and t-butyl groups would give more diversity. DMacks (talk) 19:22, 12 March 2011 (UTC)
I too agree for replacement, and I'm the one who posted it! It was my intention just to have something good enough to tide the page over until a good example, and to maybe spark it to happen. -- jslipscomb (talk) 01:48, 13 March 2011 (UTC)
Since the H-1 NMR spectrum of ethanol is discussed in the article, in particular the "Chemical shift" and the "J-Coupling" sections, in the "J-Coupling" section I added a diagram of a 1-dimensional H-1 NMR spectrum of ethanol I found in WikiCommons. It seems to be a theoretically-calculated or computer-generated picture turned into a *.gif file instead of a picture of an experimentally obtained spectrum. Few NMR spectra are available in Wikimedia, as far as I can tell. Images of NMR spectra of vanillin previously present in some NMR articles were removed because they did not have a free license. I believe most experimental NMR spectra images present on the internet are not freely licensed. H Padleckas (talk) 14:37, 24 January 2012 (UTC)

J-coupling and EFNMR[edit]

I propose adding a sentence something like this at the end of the first paragraph on J-coupling:

"J-coupling is of primary importance in Earth's field NMR because chemical shifts are insignificant in such low fields. Features such as multiplets that are separated at high fields are superimposed in EFNMR, complicating the analysis of the resulting spectra."

Any suggestions? GilesW (talk) 11:53, 30 June 2011 (UTC)

Deuterated solvents[edit]

Deuterated solvents redirects to this article but the only thing about them is the list template at the bottom. RJFJR (talk) 20:17, 4 September 2011 (UTC)

Lead is Too Long[edit]

This article's lead (the part before the table of contents) is too long. It would be great if someone knowledgeable about NMR could pare it down and move anything that needs to be preserved to its own section. Thanks! Exercisephys (talk) 15:02, 31 January 2014 (UTC)

No, it isn't. 4 paragraphs is the standard length for a lede. --vuo (talk) 17:32, 31 January 2014 (UTC)