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Image Removal
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.
--
Takometer01:58, 23 April 2006 (UTC)reply
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.
Walkerma04:25, 23 April 2006 (UTC)reply
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)reply
Work in Progress!
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!
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....
Kjaergaard06:40, 3 January 2006 (UTC)reply
Peak sizes in split peaks, style
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?
Walkerma05:37, 3 February 2006 (UTC)reply
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.
DMacks06:01, 3 February 2006 (UTC)reply
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.
Walkerma05:37, 3 February 2006 (UTC)reply
examples
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
Jhum10106:11, 25 February 2006 (UTC)reply
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)reply
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)reply
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 (
talk •
contribs)
16:56, 23 January 2014 (UTC)reply
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)reply
Virtual Coupling
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.
Ghiles10:16, 16 June 2006 (UTC)reply
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.
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 8215:00, 1 February 2007 (UTC)reply
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 BeetstraTC15:10, 1 February 2007 (UTC)reply
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)reply
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)reply
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)reply
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)reply
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.
Walkerma04:20, 28 May 2007 (UTC)reply
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."
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
76.123.153.3919:58, 30 October 2007 (UTC)reply
Spectrometer
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)reply
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)reply
iNMR
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.
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)reply
chemical shift picture
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.
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)reply
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)reply
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)reply
J-coupling and EFNMR
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."
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)reply
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