Talk:J-coupling

Physics Mid‑importance

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Chemistry Low‑importance

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Typo[edit]

Did the author in intend to say "intent pulses" or "intense pulses"? I'm changing it to intense unless someone objects..

J-value[edit]

I think J-value should redirect to this article instead of to nowhere. And perhaps a section on the numerical calculation of it? Or should there be a separate article on J-value? Jojojlj (talk) 00:12, 1 May 2011 (UTC)[reply]

Line splitting[edit]

This article does not highlight line-splitting. As that is the observable phenomenon referred to as J-coupling, also AFAIK as 'spin-spin coupling' and 'electron coupled spin-spin interactions', I feel strongly that line-splitting should be featured. See: http://www.chem.ucalgary.ca/courses/351/Carey5th/Ch13/ch13-nmr-5.html What do you think? GilesW (talk) 16:20, 29 June 2011 (UTC)[reply]

To-Do List for this Article[edit]

I don't have time right now to totally flesh out this article, but if anyone's interested, here's what I think the To-Do list should be:

Add a section on NMR line-splitting with a few examples and Pascal's Triangle
Add a real section about how J-coupling is measured (I removed the one that was there because it was not really accurate and had no real information anyway) (This is a good start)
Add a proper discussion of sign of J-coupling (similarly I removed the section because it made erroneous and uncited claims)
Provide a table of the magnitude of common J-coupling values. These are available in various tabulated forms. I would suggest at least a few orders of magnitude for 1, 2 and 3-bond couplings for H-H, C-C and C-H couplings. For the H-H couplings it's probably important to just do stuff like sp3-sp3, sp2-sp3, etc, plus some of the aromatic couplings and geminal vs. vicinal couplings are interesting. This seems like a lot, but if done right it would probably be only a few small tables, possibly placed as insets into a paragraph describing the important features.
Some description of the mechanism of the interaction. I've added a 1952 Hahn citation^{[todo 1]} which describes the mechanism. It works because the hyperfine interactions between nuclear spins and their local electrons create a net magnetic field, and since the electron cloud is somewhat delocalized across the molecule, this induces local fields in distant local fields. When you have that kind of mutual interaction, it turns out to look like a scalar coupling JI•S, where J is determined by the strength of the hyperfine interactions and the electron distribution. Presumably it's not hard to find a simple explanation of how this would be affected by bond angles and energy levels to flesh out a nice little section.

^ E. L. Hahn and D. E. Maxwell (1952). "Spin Echo Measurements of Nuclear Spin Coupling in Molecules". Phys. Rev. 88 (5): 1070–1084. doi:10.1103/PhysRev.88.1070.

0x0077BE (talk) 21:26, 25 October 2012 (UTC)[reply]

Good luck with the plans. I am hurt that you removed my section on sign of J. It is almost impossible to find info on that topic but the idea is pervasive - oh well, you try. My plea - dont turn this article into a physics-math thing. Many spectroscopy articles in Wikipedia have been ruined (IMHO) in this way. Users of NMR vastly (!) outnumber physicists, so please be kind to us idiots. I was going to say something about magnitude of J's but got distracted looking for a good list of nuclear magnetic moments (apparently does not exist in Wikipedia). Also I wished that I knew more about reduced coupling constants (corrected for the moments of the participating nuclei). Another slightly obscure theme was to remind readers that J-coupling exists even when it is not observed, i.e. the H's in CH4 are strongly coupled, its just that all the transitions have the same energy (or something like that). Maybe you can straighten me out. Final advice - be incremental. --Smokefoot (talk) 22:37, 25 October 2012 (UTC)[reply]

I actually liked most of the changes you made, but some of them felt like placeholders and had some inaccurate information, which is why I removed them from the page (to avoid confusion until someone has time to flesh them out) and put up this To Do list. As far as the direction of the page, I think most people will come looking for NMR stuff, so I think that's likely the right direction. A prominently featured section with line-splitting will help a lot in that regard, I think. --0x0077BE (talk) 22:55, 25 October 2012 (UTC)[reply]

I don't think that you should try to explain couplings through a section that is called vector-model... Maybe the author made a common mistake and confused the vector model with an energy scheme of spin-states? --16:10, 7 November 2016 (UTC) — Preceding unsigned comment added by 134.76.64.168 (talk)

J coupling or J-Coupling?[edit]

The first reference (Spin Echo Measurements of Nuclear Spin Coupling in Molecules Phys. Rev. 88, 1070–1084 (1952) ) consistently refers to scalar coupling without the dash. However, the wiki article uses it. It should be changed. Sjmantyl (talk) 07:04, 12 November 2013 (UTC)[reply]

[1] E. L. Hahn and D. E. Maxwell (1952). "Spin Echo Measurements of Nuclear Spin Coupling in Molecules". Phys. Rev. 88 (5): 1070–1084. doi:10.1103/PhysRev.88.1070.

[todo 1]