engleski

Solid-State Structure and Temperature Evacuation-Induced Dehydration of Sodium Saccharinate 1.875 Hydrate

The anion of saccharin is a polyfunctional ligand that binds to a plethora of metal ions. The solid hydrate of sodium saccharinate ("sodium saccharin" or "saccharinum soluble" ; Scheme 1) is an edible chemical which constitutes more than half of the world's artificial sweeteners, but which is suspected to be carcinogenic. Although the compound has been extensively used for more than 150 years, its exact structure has not been unequivocal1y established. In most chemical catalogues it is !isted as the dihydrate Na(sac)'2H20 (sac= C ; H4N03S-). An earlier effort to determine its crystal structure failed because of an unusuaUy large monoc1inic unit cell] and partial dehydration. Air-stable triclinic Na(sac).2/3 H20 is obtained upon recrystallization from ethano1. Herein we report the first determination of the structure of the commerciai artificial sweetener sodium saccharinate. The relative stability and the mechanisms of isobaric dehydration (heating at constant pressure ) and isothermal dehydration (evacuation at constant temperature) of the two hydrates are also revealed. Recrystallization of sodium saccharinate from different solvents yielded two hydrates. Whereas the physicochemical analysis of the hydrate obtained from 95 % ethanol was consistent with the triclinic Na(sac)• 2/3 H20 described previously, 15.61 the monoc1inic hydrate that was obtained from water was identical to the unpurified commercial product. Preci se thermoanalytical measurements of the latter showed 1.87 (1% by diffraction, see below) water molecules per formula unit.

artificial sweeteners; hydrates; IR spectroscopy; structure elucidation; X-ray diffraction

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