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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.
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