View source

From NMR Wiki

Jump to: navigation, search

Post your question about NMR, EPR or MRI on our Q&A forum

However, please this space and links below to discuss content of the corresponding wiki page.

Sorting order:
Start a new discussion about the current wiki page

Comparison of HN and CH coupings (1)

There have been no changes to this discussion for at least 14 days. If it is concluded, you may want to write a summary.

One bond HN coupling of 90 Hz was incorrectly mentioned as stronger then one bond CH coupling. CH couplings range from ~120 to ~200 Hz (aromatic).

I'm not telling about the absolute value, but for a given gyromagnetic ratio of N vs the one of C, the coupling to the proton is stronger is the case of NH than the one of CH, if N had the same gyromagnetic ratio as the carbon.

2.5*gC=gN

the JCH should be 220 Hz, and not less that 200 Hz, if the electronic configuration of the carbon was the same as the one of nitrogen.

I'm not telling about the absolute value, but for a given gyromagnetic ratio of N vs the one of C, the coupling to the proton is stronger is the case of NH than the one of CH, if N had the same gyromagnetic ratio as the carbon.

2.5*gC=gN

the JCH should be 220 Hz, and not less that 200 Hz, if the electronic configuration of the carbon was the same as the one of nitrogen.

thanks for the aromatic 1JCH coupling constant, I didn't know that it change that's much ( but hybridization state change from sp3 to sp2 ). In which case we get 120 Hz ?

According to table in "Spin dynamics" by M. Levitt, γ(15N)=-27.126 rad s-1T-1 and γ(13C)=67.283 rad s-1T-1 Gyromagnetic ratio article here also lists those values, but they are divided by a factor of 2π

so it's γN *2.5 ~ γC and J coupling values are coming in the same order JHN < JCH.

As for hybridization of carbon, smaller coupling is with sp3, larger coupling with sp2. >200 Hz for aromatics. I guess variation in coupling value with hybridization makes sense since J coupling is mediated by the electron orbitals.

You do not have permission to do that, for the following reason:

The action you have requested is limited to users in the group user.

You can view and copy the source of this page:

Return to Talk:Scalar Coupling.

Personal tools