Thermal investigations of the calcium salts of monocarboxylic aliphatic fatty acids

Calcium salts of acetic and mono, di and trichloroacetic acids were investigated with respect to their dehydration and decarboxylation, using a derivatograph. A phase transition was noticed only in the case of calcium acetate. Effects of crucible and diluent on the thermal behaviour of the above salts were also studied. The decomposition products were investigated qualitatively, and from these gaseous products and also from the residue after pyrolysis the probable mechanisms of decompositions have been suggested. Activation energies for the decarboxylation processes were evaluated from the TG curves.

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Zusammenfassung Die Calciumsalze von EssigsÄure sowie von Mono-, Di- und TrichloressigsÄure wurden mittels eines Derivatographen hinsichtlich ihrer Dehydratisierung und Decarboxylierung untersucht. Ein Phasenübergang wurde nur im Falle des Calciumacetats beobachtet. Der Effekt des Tiegels und des Verdünners auf das thermische Verhalten obiger Salze wurde ebenfalls untersucht. Die Zersetzungsprodukte wurden qualitativ geprüft und aus diesen gasförmigen Produkten sowie aus ihren Pyrolyseresten wurde ein wahrscheinlicher Zersetzungsmechanismus vorgeschlagen. Die Aktivierungsenergien der DecarboxylierungsvorgÄnge wurden aus den TG-Kurven ermittelt.

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Résumé La déhydratation et la décarboxylation des sels de calcium des acides acétique, mono, di et trichloroacétique ont été étudiées à l'aide d'un Derivatograph. Seul l'acétate de calcium présente une transition de phase. Les effets respectifs du creuset et du diluant sur le comportement thermique de ces sels ont également été suivis. Les produits de décomposition ont été analysés qualitativement. D'après la nature des gaz émis et celle des résidus de pyrolyse, un mécanisme est proposé pour ces décompositions. Les énergies d'activation des réactions de décarboxylation sont calculées à partir des courbes TG.

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The authors express their most grateful thanks to the Council of Scientific and Industrial Research, New Delhi, for financial assistance.     

Investigation and radiometric determination of saturated and unsaturated aliphatic monocarboxylic acids and aromatic dicarboxylic acids

Investigations have been carried out on the precipitation of calcium salts of saturated and unsaturated aliphatic monocarboxylic acids and of aromatic dicarboxylic acids. The optimum ethanol/water solvent ratio has been studied at which the sodium, ammonium or triethylammonium salts of the acids have a good solubility, whereas the calcium salts are poorly soluble and can be precipitated. Based on these investigations the radiometric determination of formic acid, palmitic acid, stearic acid, methacrylic acid, oleic acid, and o-, m- and p-phthalic acids has become possible. A linear correlation has been found between the solubilities of the calcium salts of o-, m- and p-phthalic acids and the dielectric constant of the solvent mixture. CaCl₂ solution labelled with⁴⁵CaCl₂ was used for the titrations, with a solvent composition identical to that of the solution to be titrated. Radiometric titrations were carried out in 0.05M solutions for dicarboxylic acids, and in 0.1M solutions for monocarboxylic acids. For palmitic and stearic acids titrations were also carried out in the 0.01M concentration range. The equipment used for titrations was capable of detecting isotopes of soft β-radiation.     

Open-framework copper adeninate compounds with three-dimensional microchannels tailored by aliphatic monocarboxylic acids

A series of isostructural copper(II) coordination polymers containing the nucleobase adenine and different monocarboxylic acids as bridging ligands, [Cu(2)(μ(3)-ade)(2)(μ(2)-OOC(CH(2))(n)CH(3))(2)]·xH(2)O (n from 0 to 5), have been prepared. Single-crystal X-ray analysis of acetate (n = 0) and butanoate (n = 2) compounds shows a covalent three-dimensional network in which the copper(II) centers are bridged by μ-N3,N7,N9-adeninato and μ-O,O'-carboxylato ligands, with crystallization water molecules trapped in the pores, which are decorated by the Watson-Crick faces of the adenine. The tunable permanent porosity of guest-free compounds was confirmed by gas adsorption measurements.     

Application of variable anti-connectivity index to active sites. Modelling pK a values of aliphatic monocarboxylic acids

A partial distance-weighted variable anti-connectivity topological index was introduced for modelling pK _a values of 31 aliphatic carboxylic acids and haloalkyl-carboxylic acids. The partial distance-weighted variable anti-connectivity index showed superior modelling capabilities compared with the index calculated from the complete graph, because it is capable of accounting correctly for the intramolecular interactions of unconnected vertices to specific bond strengths (active site), thereby improving the RMS_CV error by about 30% (0.221 pK _a units).     

Kinetics of the oxidation of aliphatic ketones by thallic salts in sulfuric acid medium

: - - 1–3 .

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With increasing partial pressure of molecules in atomic-molecular mixtures, the yield and intensity of radical-recombination luminescence of inorganic luminophors increase by 1–3 orders of magnitude.

     

Exchange characteristics of monocarboxylic acids and monosulfonic acids onto anion-exchange resins

In the previous paper (N. Kanazawa, K. Urano, N. Kokado, Y. Urushigawa, J. Colloid Interface Sci. 238 (2001) 196), the equilibria of propionic acid and benzoic acid adsorption onto three anion-exchange resins were investigated, and an equation was proposed that summed of the physical adsorption of the carboxylic acid molecule and the ion exchange of the dissociated carboxylate ion. The ion exchange equation, including a selectivity coefficient to chloride ion for each combination between carboxylate ions and anion-exchange resins, could be used in wide ranges of concentration and pH. In this research, ion-exchange equilibria using 16 anion-exchange resins and 9 organic acids including monocarboxylic and monosulfonic acids were investigated. It could be confirmed that the proposed equation applied to the ion exchange with these monoorganic acids. Characteristics of ion exchange between the organic anions and anion exchange were also studied by the selectivity coefficients.     

Acid-base equilibria in ternary water/methanol/dioxane solvent systems : Determination of pKa values of some aliphatic monocarboxylic acids

The thermodynamic acidity constants of n-butanoic, n-pentanoic, n-hexanoic, and n-heptanoic acids were determined at 25°C in ternary water/dioxane/methanol mixtures. The results obtained show that the composite medium effect, expressed by a parameter b = dpK′/du (u being a variable expressing the solvent composition), depends on the ratio of the organic co-solvent concentrations. In the ternary mixtures, superposition of the various effects detected in the corresponding binary solvents (water/dioxane and water/methanol) enables simple interpolation formulae to be used to estimate the pK_a values in solution with any ratio of the three solvents.     

The effect of different monocarboxylic acids on the gelation behaviour of Cu ethoxide

Cu ethoxide becomes soluble in methoxyethanol when formic, acetic, or acrylic acid is added. For the complete dissolution, the minimum molar ratio of an acid to Cu ethoxide is two for formic acid (HOFA), and one for acetic (HOAC) or acrylic (HOAA) acid. The solutions of Cu ethoxide with any amounts of formic acid are incapable of forming gels. Those with acetic or acrylic acid/Cu ratio of 1 are able to convert to gels. For the range of the water concentration from 1.5 to 10 M, the gelation time is strongly dependent on [H₂O] for the solution with HOAC/Cu ratio of 1, while it is almost independent for the solution with HOAA. It is suggested that the differences in the behaviour of soluble Cu species derived from the three acids are attributed to different coordination forms and the bonding strength between ligands and copper ions.     

Kinetics of oxidation of some aliphatic ketones by ditelluratocuprate(III) in alkaline medium

The kinetics of oxidation of some ketones by ditelluratocuprate(III) were followed spectrophotometrically by estimating the disappearence of potassium ditelluratocuprate(III). The reaction follows first order kinetics in both substrates and oxidant. A correlation is found between the order of reactivity and partial rates of enolization of these ketones. By assuming that the mechanism of oxidation involves the enol form of the ketone in a slow step, the observed order of reactivity of these ketones is explained.

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Palladium-catalyzed oxidation of lower aliphatic alcohols with oxygen in the presence of aromatic nitriles in aqueous medium

The kinetics of oxidation of lower aliphatic alcohols (C₁–C₄) to the corresponding carbonyl compounds with oxygen in the presence of palladium(II) tetraaqua complex and aromatic nitriles (benzonitrile, phenylacetonitrile, and o-tolunitrile) in aqueous medium (c = 0.01 M) at 65°C under atmospheric pressure were studied. A probable reaction mechanism and kinetic equation were proposed. Aromatic nitriles were found to stabilize decomposition of low-valence palladium species, ensuring activation of molecular oxygen and subsequent oxidation of alcohols.     

Depositional ice nucleation on monocarboxylic acids: effect of the O:C ratio

The heterogeneous ice nucleation efficiency of a series of thin C3-C6 monocarboxylic acid films between 180 and 200 K has been investigated using a Knudsen cell flow reactor. At each temperature, the critical ice saturation ratio for depositional nucleation as well as the effective contact angle was found to be strongly dependent on the chemical nature of the film. For the organic acids used in this study, increasing the O:C ratio lowered the supersaturation required for the onset of heterogeneous ice nucleation and decreased the effective angle of contact. This could be the result of an increase in surface hydrophilicity, which allows the film to better adsorb a metastable, icelike layer of water that serves as a template for the new phase of ice. These ice nucleation results are in excellent agreement with ice nucleation on laboratory generated α-pinene secondary organic aerosol as well as on predominantly organic particles collected in Mexico City.     

Oxidative decarboxylation of cyclohexane monocarboxylic acid III. Initiated oxidation

A mechanism is suggested for the oxidative decarboxylation of cyclohexane monocarboxylic acid initiated by decomposition of H₂O₂. The process is a non-branching chain reaction. Cyclohexanone and cyclohexanol form in termination reactions.