A  17 O NMR study of the protonation of urea | Zendy

Valentine B. | Zendy; Amour T. E. St. | Zendy; Fiat D. | Zendy

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A 17 O NMR study of the protonation of urea

Author(s) -

Valentine B.,

Amour T. E. St.,

Fiat D.

Publication year - 1984

Publication title -

organic magnetic resonance

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 0.483

H-Index - 72

eISSN - 1097-458X

pISSN - 0030-4921

DOI - 10.1002/mrc.1270221105

Subject(s) - protonation , chemistry , urea , aqueous solution , solvent , diamagnetism , chemical shift , inorganic chemistry , nuclear chemistry , nuclear magnetic resonance , organic chemistry , physics , ion , quantum mechanics , magnetic field

17 O NMR has been applied to the study of urea over a wide pH range, in fluorosulfonic acid and in magic acid (HFSO 3 SbF 5 ). A 96 ppm diamagnetic chemical shift was observed on modifying the medium from an aqueous solution at pH 3 to a fluorosulfonic acid solvent. We attributed this shift to a protonation reaction at the urea oxygen having a p K a of 0.1. A 36 ppm paramagnetic shift was observed in magic acid relative to the resonance position in fluorosulfonic acid, which is consistent with the formation of a diprotonated form of urea. Values of transverse and longitudinal relaxation rates were found to be equal as a function of pH and to double on lowering the pH from 2 to −1.

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