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Abstract  

Crystalline lamellar titanium phenylphosphonate was intercalated with n-alkylmonoamines, H3C(CH2)n-NH2 (n=0 to 3), which decomposed on heating in four distinct stages. The lamellar compound was calorimetrically titrated with ethanolic amine solution at 298.150.02 K and the enthalpy, Gibbs free energy and entropy were calculated. with the exception of butylamine, the enthalpic values increased with the number of carbon atoms in the amine chain, as -16.200.22; -18.700.19; -23.700.24 and -18.300.22 kj mol-1, from n=0 to 3. The exothermic enthalpic values reflected a favorable energetic process of intercalation, when the solvated ethanol molecules on inorganic matrix are progressively substituted by solute. The negative gibbs free energy results supported the spontaneity of the reactions and the positive favorable entropic values are in agreement with the increase of solvent molecules in the reaction medium, as the amine becomes bonded to the crystalline lamellar inorganic matrix.

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Abstract  

A new analytical method based on thermogravimetry and applied to chemically functionalized surfaces is proposed. The mass losses of surfaces modified with alkoxysilane reagents, Sup-CH2CH2CH2−R (Sup=support andR=Cl, SH, NH2, NHCONH2, NHNHCOCH3 or (CH2)4NH), are interpreted by considering the physically adsorbed water, the silanol groups and the organic moiety. The elemental analyses calculated from these data are in agreement with those obtained by classical elemental analysis. The method is quick and reproducible, and requires the use of only a few milligrams of material.

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Abstract  

A method was developed to estimate the density of the silanol groups attached to silica gel surfaces from thermogravimetric data. Depending on the mechanism of condensation of silanol groups during heating, after removing physically adsorbed water, the results obtained ranged from 4.3 to 6.7 OH nm-2 for a series of silicas. The data are in good agreement with those obtained by other techniques. Thermogravimetry proved to be a reliable tool for this kind of study, with the great advantage of being a simple, quick and inexpensive method requiring only a few mg of the silica sample.

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Abstract  

The surface of natural talc was modified with organosilanes (H3 CO)3 SiR, for R = -(CH2 )3 NH2 , -(CH2 )3 NH(CH2 )2 NH2 and -(CH2 )3 NH(CH2 )2 NH(CH2 )2 NH2 , resulting in the inorganic-organic hybrids TC1, TC2 and TC3 . These aminated talcs contain 4.38, 2.56 and 2.03 mmol g-1 of immobilized organic chains for TCx (x =1 to 3), respectively. The chemisorption isotherm data obtained by a batch wise process were adjusted to a modified Langmuir equation, to give the maximum adsorption capacity TC1 >TC2 >TC3 . The chelate effect was illustrated through calorimetric titration, giving the highest enthalpic values for TC2 and TC3 hybrids and favoured for sulfate counter anion. The enthalpic and entropic values indicated favourable reaction between copper-basic nitrogen center atoms on pendant chain covalently bonded to the inorganic backbone.

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Abstract  

Thermogravimetric data were used to calculate the number of acidic Brnsted sites in lamellar α-titanium (α-TiP), γ-titanium (γ-TiP), α-zirconium (α-ZrP) and γ-zirconium (γ-ZrP) hydrogenphosphates. The numbers of acidic sites calculated for these lamellar compounds were 7.81, 5.67, 6.33 and 5.56 for α-TiP, γ-TiP, α-ZrP and γ-ZrP, respectively. These values are in good agreement with those found through potentiometric titration. The data obtained prove that thermogravimetric measurements can be used as a reliable analytical tool to follow the ion-exchange capacity of this kind of crystalline lamellar compounds.

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Abstract  

Infrared spectroscopy, thermogravimetry and differential scanning calorimetry techniques were used to study the metal-amino acid interactions for adducts of the general formula CdCl2 nL (n=1.0 or 1.5 and L=histidine or cysteine). After characterization the thermal degradation process was kinetically followed by a non-isothermal method. The infrared data confirmed that the cation is coordinated the carboxylic oxygen atoms of the amino acid molecules. The thermogravimetric results indicated that the main step of the thermal degradation of all amino acid adducts is connected to the rupture of the metal-ligand bonds, to give the associated activation energies values of 77, 44, 55 and 41 kJ mol-1 for CdCl2 nL, n=1.0 and 1.5, for histidine and cysteine, respectively.

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Abstract  

Commercial humic acid (HA) was anchored onto silica gel (SiAPTS) previously modified with 3-aminopropyltrimethoxysilane (APTS). HA was anchored onto SiAPTS through two routes: adsorption and covalent chemical immobilization onto the surface. The adsorption occurred by adding SiAPTS to HA in an aqueous solution, producing SiHA1, while chemical immobilization was performed by reacting HA suspended in N,N-dimethylformamide with SiAPTS, to yield SiHA2. The infrared spectra confirm HA immobilization using both procedures and the termogravimetric results showed that the anchored compounds have significantly thermal stability increased. While natural HA presents a thermal stability up to 200C, the anchored compound presents a thermal stability near to 750C.

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Journal of Thermal Analysis and Calorimetry
Authors: M. Basheer, Denise Oliveira, P. Volpe, and C. Airoldi

Abstract  

A structure-activity relationship study (SAR) was applied to correlate the biological activities of m-alkoxyphenol compounds on Chromobacterium violaceum respiration with chemical structure properties. The biological activities of these compounds on metabolism rates were obtained through microcalorimetry. The calculations to estimate several physicochemical properties were carried out at the semi-empirical AM1 and ab initio DFT levels using the CEP-31G basis set and were parameterized using the continuum-solvation model COSMO for solvent contribution. m-alkoxyphenols properties were evaluated by chemometric analyses to carry out a correlation between the physicochemical properties and their biological effects. These compound effects increase with lateral hydrocarbon chain length, volume, dipole moment, proton affinity, energies of HOMO and LUMO, partition coefficient and enthalpy of formation and decrease with solvent effects and ionization enthalpy.

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