The accumulation of radical anions from 3,4-disubstituted 1,2,5thiadiazole S,S-dioxides (1) in solution of organic solvents is achieved by electrochemical, chemical and photoinduced pathways. Electrolytic and chemical reduction of 1 produces the radical anions (1 *-) in high molar yields (> ca. 80%). The survival of 1 *is measured for ca. three months. The stability of the reduced state depends on its structure and the composition (solvent, reducing agent, and supporting electrolyte) of the medium in which it is generated by the chemical and electrochemical routes. In solution of polar aprotic solvents, 1 *persists even in the presence of water or oxygen. Irradiation with 254 nm light generates 1 *but only in DMF solution; the proposed reaction mechanism involves the participation of the solvent. Radical anions are characterized by cyclic voltammetry, UV-Vis spectrophotometry and electron spin resonance spectroscopy. The chemical stability and the properties of 1/1

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Background: Eugenol is a phenolic compound with a wide spectrum of biological activities such as antibacterial and antioxidant. Objective: Eugenol is an ideal candidate as a natural antioxidant additive, especially for those substances that are affected by lipoperoxidation process, this is the case of essential oils that have an important role in the food, perfumery and pharmaceutical industries, which easily deteriorate under high temperature, strong light, and reactive oxygen species. Methods: In order to evidence the influence of the addition of eugenol in the thermal properties of Hedychium coronarium Koening essential oil, were determined the chemical composition, antioxidant properties and TG/DTG analysis after the supplementation with different ratios of eugenol/essential oil. Results: The results showed a high content of oxygenated monoteropenes (50.33%), followed by monoterpene hydrocarbons (23.35%) and sesquiterpene (19.2%), the TG/DTG analysis presented a significant increment in the degradation temperature of the essential oil, being the major value 12 ºC at a supplementation of 4.7% (v/v) of eugenol. Conclusion: Finally, the supplementation with eugenol improved the thermal stability of the essential oil of Hedychium coronarium Koening, which could be applicable to other oils thereby improving their physicochemical properties.