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Issue 4, 2003
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Protonation and phase effects on the NMR chemical shifts of imidazoles and pyrazoles: experimental results and GIAO calculations

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Abstract

The effects produced on 1H, 13C and 15N chemical shifts by protonation and by hydrogen-bonding solvents on five azoles have been determined experimentally. The following compounds have been studied: imidazole, 4,5-dimethylimidazole, pyrazole, 3,5-dimethylpyrazole and 4,5-dihydro-3-methyl-2H-benz[g]indazole. Phase effects on the 13C chemical shifts of the C-4 atom of pyrazole are discussed based both on empirical models and on GIAO calculations of absolute shieldings in different complexes. The special case of the chemical shifts of pyrazoles in the solid state, where they form multiple N–H⋯N hydrogen bonds, has also been studied theoretically.

Graphical abstract: Protonation and phase effects on the NMR chemical shifts of imidazoles and pyrazoles: experimental results and GIAO calculations

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Publication details

The article was received on 17 Oct 2002, accepted on 10 Dec 2002 and first published on 04 Mar 2003


Article type: Paper
DOI: 10.1039/B210251J
Citation: New J. Chem., 2003,27, 734-742
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    Protonation and phase effects on the NMR chemical shifts of imidazoles and pyrazoles: experimental results and GIAO calculations

    R. M. Claramunt, C. López, M. Á. García, G. S. Denisov, I. Alkorta and J. Elguero, New J. Chem., 2003, 27, 734
    DOI: 10.1039/B210251J

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