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Evidence of a phase transition of RbHCO 3 from high‐resolution solid‐state 13 C and 87 Rb NMR by comparison with KHCO 3
Author(s) -
Odin Christophe
Publication year - 2004
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1357
Subject(s) - chemistry , rubidium , monoclinic crystal system , phase (matter) , proton , crystallography , phase transition , carbon 13 nmr satellite , solid state nuclear magnetic resonance , hydrogen bond , analytical chemistry (journal) , nuclear magnetic resonance spectroscopy , nuclear magnetic resonance , crystal structure , potassium , fluorine 19 nmr , stereochemistry , molecule , physics , organic chemistry , quantum mechanics , chromatography
A variable‐temperature high‐resolution 13 C and 87 Rb solid‐state NMR study of powder rubidium hydrogencarbonate, RbHCO 3 , is presented for the first time. At ambient temperature, RbHCO 3 is formed by centrosymmetric dimers linked by hydrogen bonds, but almost no information is available on this compound concerning proton disorder and the low‐temperature phase. However, potassium hydrogencarbonate, KHCO 3 , which has an isomorphic structure for the high temperature phase, was well studied: it undergoes a non‐ferroic, non‐ferroelectric phase transition at T c = 318 K between two monoclinic structures. The protons are disordered in an asymmetric double‐well potential in the low‐temperature phase, and the double‐well potential becomes symmetric in the high‐temperature phase. By comparison with recent solid‐state NMR experimental results on KHCO 3 , we show that RbHCO 3 undergoes a phase transition at T c ≈ 245 K, and give evidence that the proton dynamic disorder in both compounds is very similar. Copyright © 2004 John Wiley & Sons, Ltd.