Étude thermodynamique des trois isomères de l'acide chlorobenzoïque. Partie II

1995 ◽  
Vol 73 (9) ◽  
pp. 1538-1545 ◽  
Author(s):  
Raphaël Sabbah ◽  
Aaron Rojas Aguilar
Keyword(s):  
Nous Avons ◽  
Resonance Energy ◽  
Combustion Calorimetry ◽  
Enthalpies Of Formation ◽  
Condensed State ◽  
Thermodynamic Quantities ◽  
Chlorobenzoic Acid ◽  
Gaseous State ◽  
Calorimetric System ◽  
Experimental Values

Our isoperibol rocking-bomb calorimeter, previously described, has been modified to: (i) reduce and stabilize the heat exchange between the calorimetric system and its surroundings; (ii) change its thermometer; (iii) associate with it a computer program for the robotics of different steps of an experiment, data acquisition, and determination of the thermodynamic quantities. After testing these modifications and calibrating the calorimetric system, the enthalpies of formation in the condensed state and at 298.15 K of the three isomers of chlorobenzoic acid have been determined by combustion calorimetry. Associating these values with those of their enthalpies of sublimation previously measured, we determined their enthalpies of formation in the gaseous state. The experimental values of the thermodynamic functions [Formula: see text] [Formula: see text] are given for 2-chlorobenzoic acid, 3-chlorobenzoic acid, and 4-chlorobenzoic acid. From the experimental value of the enthalpy of atomization, it has been possible to determine an enthalpy value for the Cb—Cl bond. The experimental and theoretical values of the resonance energy of the three isomers are compatible. The relative stability of some monosubstituted derivatives of benzoic acid studied in our laboratory is also discussed. Keywords: thermodynamics, combustion calorimetry, differential thermal analysis; 2-chlorobenzoic acid, 3-chlorobenzoic acid, 4-chlorobenzoic acid, enthalpies of combustion, of formation, resonance energy, enthalpies of atomization, of intramolecular bonds, reference material.Notre calorimètre isopéribolique à bombe rotative, précédemment décrit, a été modifié: (i) en diminuant et en stabilisant les échanges thermiques entre le système calorimétrique et le milieu extérieur; (ii) en modifiant son thermomètre de mesure; (iii) en lui associant un système informatisé de robotique, d'acquisition et de traitement des signaux thermiques. Après avoir vérifié la bonne marche de l'appareil ainsi modifié et réalisé l'étalonnage du système calorimétrique, nous avons déterminé à 298,15 K et par calorimétrie de combustion les enthalpies de formation à l'état condensé des trois isomères de l'acide chlorobenzoïque. En associant ces valeurs à celles de leurs enthalpies de sublimation à 298,15 K, nous avons pu déterminer leurs enthalpies de formation à l'état gazeux. Les valeurs expérimentales des fonctions thermodynamiques [Formula: see text] [Formula: see text] sont données pour les acides 2-chloro-benzoïque, 3-chlorobenzoïque et 4-chlorobenzoïque. À partir de l'enthalpie d'atomisation expérimentale de ces trois acides, une valeur enthalpique a été proposée pour la liaison Cb—Cl dans ce type de composés. Les valeurs expérimentale et théorique de l'énergie de conjugaison sont compatibles. Une discussion sur la stabilité relative de quelques dérivés monosubstitués de l'acide benzoïque étudiés au laboratoire est aussi développée. Motsclés: thermodynamique, calorimétrie de combustion, analyse thermique différentielle; acide 2-chlorobenzoïque, acide 3-chlorobenzoïque, acide 4-chlorobenzoïque, enthalpies de combustion, de formation, énergie de conjugaison, enthalpies d'atomisation, de liaisons intramoléculaires, substance d'intercomparaison.

Influence of the functional groups −NH2, −OCH3, and −OH on the thermochemistry of indanes

2019 ◽  
Vol 97 (11) ◽  
pp. 788-794
Author(s):  
Ana L.R. Silva ◽  
Paula M.V. Gama ◽  
Maria D.M.C. Ribeiro da Silva
Keyword(s):  
Enthalpy Of Formation ◽  
Gaseous Phase ◽  
Molar Enthalpy ◽  
Enthalpies Of Formation ◽  
Condensed State ◽  
Calvet Microcalorimetry ◽  
Energy Of Combustion ◽  
Experimental Values ◽  
Enthalpies Of Sublimation

This work is a contribution to the thermochemical characterization of bicyclic hydrocarbons, reporting the study of six indane derivatives: 4-aminoindane, 5-aminoindane, 5-methoxyindane, 1-indanol, 2-indanol, and 5-indanol. The combustion calorimetry technique was used to measure the massic energy of combustion of each compound in the condensed state, which has been used to derive the corresponding standard (p° = 0.1 MPa) molar enthalpy of formation, at 298.15 K. The standard molar enthalpies of sublimation or vaporization of the compounds were determined by high-temperature Calvet microcalorimetry. For each indane derivative, the results obtained for those two properties, allowed to derive the respective value of standard molar enthalpy of formation, in the gaseous phase. Additionally, a theoretical study at the G3(MP2)//B3LYP level has been carried out, and the calculated enthalpies of formation have been compared with the experimental values. The values of the enthalpy of formation, in the gaseous phase, were analysed in terms of correlations between the structural (different substituents in the indane core) and energetics characteristics.

Étude thermodynamique des acides phtalique, isophtalique et téréphtalique

1999 ◽  
Vol 77 (9) ◽  
pp. 1508-1513 ◽  
Author(s):  
Raphaël Sabbah ◽  
Laurence Perez
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Resonance Energy ◽  
Intermolecular Forces ◽  
Enthalpies Of Formation ◽  
Enthalpy Of Sublimation ◽  
Gaseous State ◽  
Combustion Enthalpy ◽  
The One ◽  
Triple Point Temperature

A thermodynamic study of phthalic, isophthalic, and terephthalic acids (general formula: C8H6O4) was carried out by sublimation calorimetry and differential thermal analysis. With values of combustion enthalpy taken from the literature, it was possible to determine their enthalpies of formation in the gaseous state and at 298.15 K and their resonance energy. The results enabled us to do a comparative study of the relative stability of the three acids, on the one hand, and of different benzene disubstituted derivatives, on the other hand. From the enthalpy of sublimation, it was possible to determine the energetic contribution of the different intermolecular forces in the crystals of the three acids.Key words: thermodynamic, calorimetry, differential thermal analysis, phthalic, isophthalic, terephthalic acids, enthalpy of fusion, of sublimation, of formation, of intermolecular bonds, resonance energy, triple point temperature.

scholarly journals An approach to determine enthalpies of formation for ternary compounds

2010 ◽  
Vol 46 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Y. Du ◽  
J. Wang ◽  
Y.F. Ouyang ◽  
L.J. Zhang ◽  
Z.H. Yuan ◽  
...  
Keyword(s):  
Experimental Data ◽  
First Principles ◽  
Integrated Approach ◽  
Enthalpies Of Formation ◽  
Calphad Approach ◽  
Miedema Model ◽  
Theoretical Computation ◽  
Ternary Compounds ◽  
Data Yield ◽  
Experimental Values

An integrated approach of experiment and theoretical computation to acquire enthalpies of formation for ternary compounds is described. The enthalpies of formation (DHf ) for Al71Fe19Si10 and Al31Mn6Ni2 are measured via a calorimeter. Miedema model, CALPHAD and first-principles method are employed to calculate DHf for the above compounds and several Al-based ternary compounds. It is found that first-principles generated data yield good agreements with experimental values and thus can be used as key 'experimental data', which are needed for CALPHAD approach.

The Enthalpies of Formation ofo-,m-, andp-Benzoquinone:  Gas-Phase Ion Energetics, Combustion Calorimetry, and Quantum Chemical Computations Combined

2005 ◽  
Vol 127 (16) ◽  
pp. 6116-6122 ◽  
Author(s):  
Alireza Fattahi ◽  
Steven R. Kass ◽  
Joel F. Liebman ◽  
M. Agostinha R. Matos ◽  
Margarida S. Miranda ◽  
...  
Keyword(s):  
Gas Phase ◽  
Quantum Chemical ◽  
Combustion Calorimetry ◽  
Enthalpies Of Formation ◽  
Gas Phase Ion ◽  
Quantum Chemical Computations

The standard molar enthalpies of formation of α−Si3N4 and β−Si3N4 by combustion calorimetry in fluorine, and the enthalpy of the α-to-β transition at the temperature 298.15 K

1997 ◽  
Vol 12 (12) ◽  
pp. 3203-3205 ◽  
Author(s):  
P. A. G. O'Hare ◽  
Iwona Tomaszkiewicz ◽  
H. J. Seifert
Keyword(s):  
Combustion Calorimetry ◽  
Enthalpies Of Formation ◽  
Experimental Uncertainty

The standard molar enthalpies of formation ΔfH°m of α−Si3N4 and β−Si3N4 have been determined by fluorine combustion calorimetry: ΔfH°m (Si3N4, cr, α, 298.15 K) = − (828.9 ± 3.4) kJ · mol−1 and ΔfH°m (Si3N4, cr, β, 298.15 K) = – (827.8 ± 2.5) kJ · mol−1. These results indicate that the enthalpy of the α-to-β transition, approximately (1 ± 4) kJ · mol−1, is negligible within experimental uncertainty.

Enthalpies of formation of tin (IV) and tin (II) oxides from combustion calorimetry

1981 ◽  
Vol 13 (7) ◽  
pp. 635-646 ◽  
Author(s):  
E.G. Lavut ◽  
B.I. Timofeyev ◽  
V.M. Yuldasheva ◽  
E.A. Lavut ◽  
G.L. Galchenko
Keyword(s):  
Combustion Calorimetry ◽  
Enthalpies Of Formation

scholarly journals COMPARATIVE CHARACTERISTICS OF COATINGS WITH SiO AND GeO ON LEUCOSAPPHIRE

2021 ◽  
Vol 26 (2(78)) ◽  
pp. 14-21
Author(s):  
V.F. Zinchenko ◽  
I. R. Magunov ◽  
O. V. Mozkova ◽  
B. A. Gorshtein ◽  
V. P. Sobol’ ◽  
...  
Keyword(s):  
Solid Surface ◽  
Multilayer Coating ◽  
Contact Angles ◽  
Qualitative Assessment ◽  
Condensed State ◽  
Multilayer Coatings ◽  
Gaseous State ◽  
Film Forming ◽  
Spectral Ranges ◽  
First Moment

The reasons for the sharp difference in the adhesion of multilayer coatings containing SiO or GeO together with Ge on a leucosapphire (Al2O3) plate have been established. It should be mentioned that Silicon(II) and Germanium(II) oxides are quite stable in the gaseous state and, contrary, are metastable in condensed state; at high temperature they disproportionate into ultra-dispersed composites of amorphous nature. A comparison is made of the surface properties of ultramicroscopic droplets formed on solid surfaces – a substrate or the previous layer – upon condensation of SiO, GeO, or Ge vapors on leucosapphire. A qualitative assessment of the ratio of the corresponding contact angles of wetting by the indicated melts, formed at the first moment of contact, has been carried out. In assessing the surface tension of SiO and GeO melts (or Si – SiO2 and Ge – GeO2 composites), we proceeded from the corresponding values for SiO2 and GeO2, which are 296 and 248 mJ/m2 near the crystallization temperatures. On this basis, it was established that the smallest value of the contact angle, and hence the best wetting, is observed for the GeO melt (somewhat less for the SiO melt) on the solid surface of Al2O3 or Ge; the solid surface of SiO or GeO (especially, the first of them) with molten germanium should be much weaker wetted. Hence, it follows that thin-film multilayer coatings obtained from Ge and GeO on a leucosapphire substrate should have a significantly higher climatic resistance due to higher adhesion compared to multilayer coatings from SiO and Ge. Indeed, a multilayer coating containing SiO on a leucosapphire substrate with a large surface can withstand storage in air for no more than 2–3 months and begins to peel off; at the same time, the GeO coating remains intact after 4 years of storage. Thus, the GeO film-forming material is a promising one for use in multilayer coatings such as cut-off filters in interference optics of the near and mid-IR spectral ranges.

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