engleski

Structure of sodium saccharinate 1.875 hydrate, Na64(C7H4NO3S)64∙ 120H2O

The deprotonated saccharin (C7H4NO3S– ) is a polyfunctional ligand that binds to plethora of metal ions. The hydrate of sodium saccharinate is an edible chemical which constitutes more than half of the world’ s artificial sweeteners, but is suspected to be carcinogenic. In most chemical catalogues it is listed as the dihydrate Na(sac)∙ 2H2O (sac = C7H4NO3S– ), but after about 150 years of its extensive use the exact structure of this compound has not been established. An earlier effort to determine its crystal structure failed because of an unusually large monoclinic unit cell [G. Jovanovski, PhD thesis, University of Zagreb, 1981] and partial dehydration. Air-stable triclinic Na(sac)∙ ⅔ H2O is obtained upon recrystallization from ethanol [G. Jovanovski, B. Kamenar, Cryst. Struct. Commun. 11 (1982) 247– 249 ; G. Jovanovski, O. Grupče, B. Šoptrajanov, J. Mol. Struct. 219 (1990) 61-66]. Here we report the first determination of the structure of the commercial artificial sweetener sodium saccharinate. The structure may be regarded as an occupational and displacive modulation of an idealized (i) structure with C2/m Z = 8 symmetry, whereby ai = a, bi = b/4 and ci = c/2. The large number of structurally different water molecules is confirmed by the matrix-isolation spectra of the partially deuterated compound.

metal saccharinates ; modulated structure ; commercial sweetener ; crystal structure ; hydrates ; crystal polymorphs

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