Thermal decomposition of metal p-hydroxybenzoates (in Russian)
The thermal decomposition of the p-hydroxybenzoato complexes of divalent Mg, Mn, Co, Ni, Zn, Cu, Cd, and Ba has been studied under dynamic conditions in air in the 20-1000/sup 0/C temperature range. It has been found that the polyaquo complexes of Mg, Mn, Co, Ni, Zn, and Cu form a series of isomorphous compounds, whose structures consist of octahedral (M(H/sub 2/O)/sub 6//sup 2 +/ aquo ions /or an (Cd(H/sub 2/O)/sub 5/(PHB))/sub 2//sup +/ ion in the case of the Cd complex/, two anions of the acid, and two molecules of water of crystallization. The temperature ranges for the existence of the intermediate phases with low water contents and anhydrous phases have been established. The destruction of the anhydrous complexes takes place with the release of p-hydroxybenzoic acid and the formation of stable intermediates. The Mn, Cd, and Ni complexes decompose with the release of 1 mole of p-hydroxybenzoic acid, while the Mg, Co, and Zn complexes decompose with the release of 0.5 mole of the acid. The thermal stability of the anhydrous complexes decreases along the series Cd > Mn > Mg > Co > Cu > Zn > Ni. The stable phases have been identified by the methods of thin-layer chromatography, chemical analysis, x-ray diffraction analysis, and x-ray structural analysis, the crystal structure of the intermediate triaquo(hydroxybenzoato)manganese has been interpreted, and a structure has been proposed for anhydrous zinc p-hydroxybenzoate. It has been shown that the polyaquo Mn, Cd, and Zn complexes are converted into isomeric hydrates at 35-55/sup 0/C as a consequence of the displacement of the two weakly bound water molecules located in trans positions to one another to the hydration shell of the metal by O atoms of the COO groups of two p-hydroxybenzoate anions. The final thermolysis products are the oxides of the respective metals and BaCO/sub 3/. The Ni, Co, and Cu complexes initially decompose to the free metal, which then undergoes oxidation.
- OSTI ID:
- 6476467
- Journal Information:
- Sov. J. Coordinat. Chem.; (United States), Vol. 12:1; Other Information: Translated from Koordinatsionnaya Khimiya, 12: No. 1, 37-46(Jan 1986)
- Country of Publication:
- United States
- Language:
- Russian
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
BARIUM COMPLEXES
PYROLYSIS
CADMIUM COMPLEXES
COBALT COMPLEXES
COPPER COMPLEXES
MAGNESIUM COMPLEXES
MANGANESE COMPLEXES
NICKEL COMPLEXES
ZINC COMPLEXES
ANHYDRIDES
BARIUM OXIDES
CADMIUM OXIDES
CARBOXYLIC ACIDS
CATALYTIC EFFECTS
COBALT OXIDES
COPPER OXIDES
CRYSTAL STRUCTURE
DIFFERENTIAL THERMAL ANALYSIS
HYDROXY COMPOUNDS
MAGNESIUM OXIDES
MANGANESE OXIDES
NICKEL OXIDES
PYROLYSIS PRODUCTS
STRUCTURAL CHEMICAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
THIN-LAYER CHROMATOGRAPHY
X-RAY DIFFRACTION
ZINC OXIDES
ALKALINE EARTH METAL COMPLEXES
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CADMIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
CHROMATOGRAPHY
COBALT COMPOUNDS
COHERENT SCATTERING
COMPLEXES
COPPER COMPOUNDS
DECOMPOSITION
DIFFRACTION
GRAVIMETRIC ANALYSIS
MAGNESIUM COMPOUNDS
MANGANESE COMPOUNDS
NICKEL COMPOUNDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
QUANTITATIVE CHEMICAL ANALYSIS
SCATTERING
SEPARATION PROCESSES
THERMAL ANALYSIS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENT COMPOUNDS
ZINC COMPOUNDS
400201* - Chemical & Physicochemical Properties
360602 - Other Materials- Structure & Phase Studies