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Article Dans Une Revue Journal of Molecular Structure Année : 2011

A 13C NMR Study of pyridinium phenoxide series with increasing sterical hindrance reveals the dramatic influence of torsion on their structure

Résumé

The 13C resonance signals of five twisted pyridinium phenoxides has been assigned in two different solvents (CD3OD and D6-DMSO), while the torsion angle was varied by changing the pyridinium substituents at ortho positions of the intercyclic bond. The experimental 13C chemical shifts of these compounds were adjusted using calculating shift parameters evaluated from reference compounds, revealing the changes of 13C signals due to the different interplanar angles. A dramatic modification of the structure was observed as the angle increases (transition from quinone form to zwitterion one), adding a piece of information on the still debated question: the relative contributions of the two limit forms (quinone, zwitterion) in a pyridinium phenoxide series. Then the ability of four other twist compounds, bearing no ‘‘protected’’ groups at ortho position of the phenoxide function, to rapid deuteration was studied. This property is once more related to the twist structure of pyridinium phenolates.
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Dates et versions

hal-01151415 , version 1 (31-08-2017)

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Hélène Chaumeil, Patrice Jacques, Vincent Diemer, Didier Le Nouen, Christiane Carré. A 13C NMR Study of pyridinium phenoxide series with increasing sterical hindrance reveals the dramatic influence of torsion on their structure. Journal of Molecular Structure, 2011, 1002 (1-3), pp.70-75. ⟨10.1016/j.molstruc.2011.06.049⟩. ⟨hal-01151415⟩
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