The conditions of thermal decomposition of scandium(l I I) hemimellitate, trimellitate and trimezinate in air and nitrogen atmospheres have been studied. On heating, the benzenetricarboxylates of Sc(lll) decompose in two stages. First, the hydrated complexes lose crystallization water; heating in air finally yields Sc20 3, and heating in a nitrogen atmosphere Sc20 3 and C. The dehydration of the complexes is associated with strong endothermic effects. Thedecomposition of benzenetricarboxylates in air is accompanied by an exothermic effect and in nitrogen by an endothermic effect.The activation energies of the dehydration and decomposition reactions have been calculated for the Sc(I I I) benzenetricarboxylates. (lll) have not been studied so far. As a continuation of our work on the thermal decomposition of scandium(Ill) carboxylates [5][6][7], we now report the thermal decomposition of scandium(l I I) benzenetricarboxylates in air and nitrogen atmospheres.
ExperimentalScandium(Ill) benzenetricarboxylates were prepared in double decomposition reactions by adding ammonium hemimellitate (pH 5.8), trimellitate (pH 4.6) or trimezinate (pH 5.6) to a hot solution containing Sc(lll)nitrate (0.1 M). The precipitate formed was heated in the mother liquor for 1 h, then filtered off, washed with water to remove NH~ ions and dried at 30 ~ to constant mass.
The conditions of thermal decomposition of scandium(lll) m-nitrobenzoate, mchlorobenzoate, m-hydroxybenzoate and m-aminobenzoate were studied. On heating, most of these carboxylates decompose in two steps; only scandium(Ill) 3-aminobenzoate decomposes in one step. The hydrated complexes first lose crystallization water and are then transformed to Sc20 3. The hydration of the complexes is accompanied by an endothermic effect, and the decomposition of the anhydrous complexes by a strong exothermic effect. Scandium(Ill) 3-nitrobenzoate decomposes explosively.Rare earth element complexes with m-benzoic acids are little known, mHydroxybenzoates of Y, La and lanthanides have been prepared as hydrated salts with a metal to ligand ratio of 1 : 3 [1-4], their IR and X-ray spectra have been recorded and their thermal decompositions in air and nitrogen atmospheres have been studied. Pirkes et al. [5] isolated La, Ce(III), Pr(III), Nd and Sm(III) mnitrobenzoates with general formula Ln(NO2C6H4COO)3 9 2H20. During heating to 300 ~ these complexes are decomposed, m-Chlorobenzoates and maminobenzoates of rare earth elements have not been prepared.Scandium(III) complexes with m-benzoic acids have not been studied so far. The aim of our work was to obtain the m-nitrobenzoate, m-chlorobenzoate, mhydroxybenzoate and m-aminobenzoate of scandium(III) and to examine their thermal decompositions in air atmosphere.
The thermal decompositions of scandium 2,4-dinitrobenzoate, 3,5-dinitrobenzoate, 2,4-dichlorobenzoate and 3,4-diaminobenzoate were studied. On hea~ing, the carboxylates decompose in two steps. The hyd~rated complexes first lose crystallization water and are transformed to Sc203. The dehydration of the complexes is accompanied by an endothermic effect and decomposition of the anhydrous or monohydrate complezes by strong exothermic effects. Scandium 2,4-dinitrobenzoate and 3,5-dinitrobenzoate decompose explosively.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.