Synthesis, structure, spectroscopic, and thermal properties of organic-based new salts of acesulfame and saccharin

In this thesis study, compounds including nicotinamidium acesulfamate, triethanolammonium acesulfamate, nicotinamidium saccharinate, triethanolammonium saccharinate, 2-amino-3-hydroxypyridinium saccharinate, 4-aminopyridinium saccharinate, and anilinium saccharinate were synthesized. Based on elemental analysis results, it was determined that these synthesized compounds form 1:1 salts through acid-base or ion exchange reactions. The characteristic vibrational frequencies related to the functional groups of these synthesized compounds were determined, and the similarities and differences in bonding modes, structures, and substituent groups were discussed. It was observed that the carbonyl stretching vibrations (ν(C=O)) appearing at 1674 cm-1 in acesulfamic acid and 1715 cm-1 in saccharin shift to lower frequencies in all acesulfamate and saccharinate salts. Furthermore, the 1H-NMR spectrum of 2-amino-3-hydroxypyridinium saccharinate was thoroughly evaluated. The synthesized salts were subjected to simultaneous recording of TG, DTG, and DTA curves in a static atmospheric environment, and the thermal decomposition mechanisms and thermal stabilities were discussed in detail. According to their thermal behavior, it has been observed that the synthesized compounds, namely nicotinamidium acesulfamate (135 ºC), triethanolaminium acesulfamate (205 ºC), and aniliniumium saccharinate (188 ºC), Simultaneous occurrence of melting and degradation has been observed. In contrast, it was observed that nicotinamidium saccharinate (137 ºC), triethanolaminium saccharinate (80.7 ºC), 2-amino-3-hydroxypyridinium saccharinate (195 ºC), and 4-aminopyridinium saccharinate (179 ºC) were melted. Considering the maximum decomposition temperatures (DTGmax) of the newly synthesized compounds, the thermal stability order was found as: nicotinamidium saccharinate (169 ºC) < triethanolaminium acesulfamate (205 ºC) < anilinium saccharinate (209 ºC) < triethanolaminium saccharinate (236 ºC) < nicotinamidium saccharinate (281 ºC) < 2-amino-3-hydroxypyridinium saccharinate (305 ºC) < 4-aminopyridinium saccharinate (324 ºC). Nicotinamidium saccharinate remains stable in the liquid state within the temperature range of 137-190 °C, triethanolaminium saccharinate within the range of 80.7-200 °C, 2-amino-3-hydroxypyridinium saccharinate within the range of 195-220 °C, and 4-aminopyridinium saccharinate within the range of 179-245 °C. Therefore, it can be observed that these newly synthesized salts, composed of an organic cation and an organic anion, exhibit ionic liquid characteristics. Nicotinamidium saccharinate, 4-aminopyridinium saccharinate, 2-amino-3-hydroxypyridinium saccharinate, and nicotinamidium acesulfamate crystal structures were elucidated using X-ray single crystal diffraction method. It was observed that the saccharin anion undergoes proton transfer from the imine nitrogen to the pyridine's nitrogen of nicotinamide, 4-aminopyridine, and 2-amino-3-hydroxypyridine, forming 1:1 salts. Similarly, in acesulfamate, proton transfer from the imine nitrogen to the pyridine's nitrogen of nicotinamide was observed. Nicotinamidium saccharinate and 4-aminopyridinium saccharinate were determined to have a triclinic crystal system, while 2-amino-3-hydroxypyridinium saccharinate and nicotinamidium saccharinate were found to have a monoclinic crystal system.