Concentration Shift of Nuclear Magnetic Resonances in Some Concentrated Acids

概要

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Chemical shifts of nuclear magnetic resonances are caused when two nuclei of the same kind have different magnetic shieldings caused by their environments. When there are two species of molecules having a chemical shift between them and if they are exchanging their states very rapidly by chemical reaction, we cannot observe their nuclear magnetic resonances separately but we observe a single resonance at the position of the field averaged over the two states with a weight of their populations. We observed such resonances for N^<14>, Cl^<35>, Br^<81> and I^<127> in concentrated aqueous solutions of HNO_3, HClO_4, HCl, HBr and HI, respectively. In these cases, the chemically exchanging states are ions and undissociated molecules and from the measurements of the shifts we can get some knowledge of the concentrated acid solutions, such as the degrees of dissociation, the type of the undissociated molecule and so on. All the nuclei examined here have the quadrupole moments, and from the measured line width in HCl, HBr and HI, we concluded that the undissociated molecules are not the HCl, HBr and HI molecules which possess large quadrupole couplings but some other molecules which have much smaller quadrupole couplings.
社団法人日本物理学会の論文
1954-02-25