Determination of the relative signs of the spin-spin interaction constants in some N¹⁵-substituted organonitrogen compounds

Conclusions

The determination of the absolute values and signs of the SSIC$J_{N^{15} - H}$ has great value both for investigating the electronic structure of organonitrogen compounds and for verifying and developing the theory of spin-spin interaction. It has been recently disclosed [8–10] that the magnitudes of the direct, geminal, and vicinal SSIC$J_{N^{15} - H}$ depend on the dielectric constant of the solvent on its protonation. In addition, the sign of the geminal SSIC$J_{N^{15} - H}$ in oximes depends on the configuration of the latter [8, 9].

The signs of the SSIC that we determined agree with those found earlier for some organonitrogen compounds [6, 8, 11–15] and add to those mentioned above the instance when one of the protons, which is directly bonded to the nitrogen, froms an intramolecular hydrogen bond. It is interesting that the geminal SSIC$J_{N^{15} - H}$ in compound II is zero. This agrees with the fact that the geminal SSIC changes sign upon passing through zero. At the same time, the vicinal SSIC J_H-H differs from zero and is larger than the geminal SSIC J_H-H in compound I.