Étude thermodynamique des trois isomères de l'acide hydroxybenzoïque

1993 ◽  
Vol 71 (9) ◽  
pp. 1378-1383 ◽  
Author(s):  
Raphaël Sabbah ◽  
Thi Huy Duc Le
Keyword(s):  
Thermal Analysis ◽  
Heat Capacity ◽  
Differential Thermal Analysis ◽  
Thermodynamic Study ◽  
Experimental Results ◽  
Ortho Isomer ◽  
Resonance Energies ◽  
Hydroxybenzoic Acids ◽  
Heat Capacity Measurements ◽  
Good Agreement

A thermodynamic study of the three hydroxybenzoic acids was carried out by combustion and sublimation calorimetry, heat capacity measurements, and differential thermal analysis. The experimental results (in kJ mol−1) are summarized as:[Formula: see text]From these experimental results, it was possible to determine for the three isomers (i) the resonance energies. From their comparison, the ortho isomer seems to be the most stable. This result is discussed using a structural consideration; (ii) the enthalpies of atomization. These values are in good agreement with that calculated using a contribution method.

Energetics of Intra- and Inter-molecular Bonds in the Three Nitrophenols

1994 ◽  
Vol 47 (9) ◽  
pp. 1651 ◽  
Author(s):  
R Sabbah ◽  
M Gouali
Keyword(s):  
Thermal Analysis ◽  
Hydrogen Bond ◽  
Heat Capacity ◽  
Differential Thermal Analysis ◽  
Relative Stability ◽  
Intermolecular Bond ◽  
Resonance Energies ◽  
Heat Capacity Measurements ◽  
Intramolecular Hydrogen ◽  
Good Agreement

A thermodynamic study of the three nitrophenol isomers (general formula C6H5NO3) was realized by combustion calorimetry of small amounts of substance (a few milligrams), sublimation calorimetry, differential thermal analysis and heat capacity measurements. The experimental enthalpies of combustion, sublimation and fusion of these compounds are as follows: ortho para -ΔcH�m(s,298.15K)/kJ mol-1 2871.0�1.3 2875.1�0.9 2868.5�1.0 ΔsubH�m(298.15K)/kJ mol-1 72.30�0.28 91.23�0.49 92.39�0.43 ΔfusHm/kJ mol-1 18.32�0.35 20.54�0.34 17.33�0.10 Ttriple point/K 318.40�0.01 370.51�0.01 387.26�0.05   The strength of the intramolecular hydrogen bond in the ortho isomer was estimated equal to 20.09 kJ mol-1. The relative stability of the three isomers is discussed, and the intermolecular bond enthalpies have been determined. The experimental resonance energies Eexp,conj are 168.7, 142.8 and 148.2 kJ mol-1 for ortho -, meta- and para-nitrophenol respectively, and are in good agreement with theoretical values. The experimental atomization enthalpies Δa,expH°m(298.15K) are 6742.5�1.9, 6719.5�1.7 and 6724.9�1.8 kJ mol-1 for ortho -, meta- and para-nitrophenol respectively.

Energetics of Intramolecular Bonds in 1H-1,2,4-Triazole and 1H-Benzotriazole

1999 ◽  
Vol 52 (4) ◽  
pp. 235 ◽  
Author(s):  
Raphaël Sabbah ◽  
Laurence Perez
Keyword(s):  
Thermal Analysis ◽  
Heat Capacity ◽  
Differential Thermal Analysis ◽  
General Formula ◽  
Triple Point ◽  
Thermodynamic Quantity ◽  
Atomization Enthalpy ◽  
A Value ◽  
Resonance Energies ◽  
Heat Capacity Measurements

This paper deals with a thermodynamic study of 1H-1,2,4-triazole and 1H-benzotriazole (general formula C2H3N3 and C6H5N3 respectively). Investigations were performed by combustion calorimetry of small amounts of substance (a few milligrams), sublimation calorimetry, differential thermal analysis and heat capacity measurements. The experimental combustion, sublimation and fusion enthalpies of the two compounds were determined as well as their triple point temperatures and are as follows: From these results, experimental resonance energies have been obtained and compared with theoretical values. The experimental atomization enthalpy of 1H-1,2,4-triazole is compatible with the calculated value. In the case of 1H-benzotriazole, it was possible to determine from this thermodynamic quantity a value of 298·4 kJ mol-1 for the N=N bond enthalpy.

Energétique des liaisons inter- et intramoléculaires dans les trois isomères du benzènediamine

1997 ◽  
Vol 75 (4) ◽  
pp. 357-364 ◽  
Author(s):  
Raphaël Sabbah ◽  
Laurence Perez
Keyword(s):  
Thermal Analysis ◽  
Hydrogen Bond ◽  
Heat Capacity ◽  
Differential Thermal Analysis ◽  
Triple Point ◽  
Relative Stability ◽  
Enthalpy Of Combustion ◽  
Resonance Energies ◽  
Heat Capacity Measurements ◽  
Intramolecular Hydrogen

The present work is concerned with a thermodynamic study of the three benzenediamine (BDA) isomers (general formula: C6H8N2). It was achieved using four techniques: combustion calorimetry of small amounts of substance (a few milligrams), sublimation calorimetry, differential thermal analysis, and heat capacity measurements. From this study it was possible: to determine the enthalpies of combustion; sublimation, and fusion of these compounds as well as their triple point temperatures; to discuss the relative stability of the three molecules; to determine the experimental resonance energies and to compare them with the theoretical values; to determine the atomization enthalpies and to compare them with the values calculated from the energetical contributions previously obtained in our laboratory; to determine the intermolecular enthalpy bonds; to consider the existence of an intramolecular hydrogen bond in the ortho isomer. Keywords: benzenediamine isomers; enthalpy of combustion, of sublimation, of fusion, of inter- and intramolecular bonds.

Energétique des liaisons inter- et intramoléculaires dans les trois isomères de l'aminopyridine

1998 ◽  
Vol 76 (1) ◽  
pp. 18-24 ◽  
Author(s):  
Raphaël Sabbah ◽  
Maria Ermelinda da Silva Eusébio
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
General Formula ◽  
Triple Point ◽  
Relative Stability ◽  
Combustion Calorimetry ◽  
Thermodynamic Study ◽  
Enthalpy Of Combustion ◽  
Resonance Energies

The present work is concerned with a thermodynamic study of the three aminopyridine (AP) isomers (general formula: C5H6N2). It was achieved using three techniques: combustion calorimetry of small amounts of substance (a few milligrams), sublimation calorimetry, and differential thermal analysis. From this study, it was possible to determine the enthalpies of combustion, sublimation, and fusion of these compounds and their triple point temperatures; to discuss the relative stability of the three molecules; to determine the experimental resonance energies and compare them with the theoretical values; to determine the atomization enthalpies and compare them with the values calculated from the energetical contributions previously determined in our laboratory; to determine the enthalpy of the intermolecular bonds.Key words: aminopyridine isomers; enthalpy of combustion, of sublimation, of fusion, of inter- and intramolecular bonds.

Energétique des liaisons inter et intramoléculaires dans les trois isomères de l'aminophénol

1996 ◽  
Vol 74 (4) ◽  
pp. 500-507 ◽  
Author(s):  
Raphaël Sabbah ◽  
Meriem Gouali
Keyword(s):  
Thermal Analysis ◽  
Hydrogen Bond ◽  
Differential Thermal Analysis ◽  
Resonance Energy ◽  
Enthalpy Of Combustion ◽  
Atomization Enthalpy ◽  
Resonance Energies ◽  
Heat Capacity Measurements ◽  
Intramolecular Hydrogen ◽  
Triple Point Temperature

The prsesent work is concerned with a thermodynamic study of the three aminophenol isomers (general formula: C6H7NO). It was achieved using four techniques: combustion calorimetry of small amounts of substance (a few milligrams), sublimation calorimetry, differential thermal analysis, and heat capacity measurements. From this study, it was possible: to determine the enthalpies of combustion, sublimation, and fusion of these compounds; to discuss the relative stability of the three molecules; to determine the intermolecular enthalpy bonds; to determine the experimental resonance energies and to compare them with the theoretical values; to determine the atomization enthalpies and to compare them with the values calculated from the energetical contributions previously determined in our laboratory; to consider the existence of an intramolecular hydrogen bond in the ortho isomer. Key words: thermodynamics; thermochemistry; calorimetry; differential thermal analysis; 2-aminophenol or ortho-aminophenol; 3-aminophenol or meta-aminophenol; 4-aminophenol or para-aminophenol; enthalpy of combustion, of sublimation, of fusion, of atomization, enthalpy of inter and intramolecular bonds; hydrogen bond; resonance energy; triple point temperature.

scholarly journals DTA measurements in the ternary Ag-Au-Ga system

2020 ◽  
pp. 21-21
Author(s):  
Dominika Jendrzejczyk-Handzlik ◽  
Piotr Handzlik
Keyword(s):  
Experimental Data ◽  
Thermal Analysis ◽  
Phase Diagram ◽  
Differential Thermal Analysis ◽  
Phase Transformations ◽  
Cross Sections ◽  
Calphad Method ◽  
Experimental Results ◽  
Zero Rate ◽  
Good Agreement

In this work, the ternary Ag-Au-Ga system was studied experimentally by differential thermal analysis (DTA). Measurements were carried out along two chosen cross-sections determined by the ratio of mole fractions XAg/XGa=1:1 and XAu/XGa=1:1 by applying Pegasus 404 apparatus form Netzsch. Experiments were performed at three rates: 1 K min-1, 5 K min-1 and 10 K min-1. Next, the obtained experimental results were used to estimate the temperatures of liquidus by applying extrapolation to zero rate. Moreover, the temperatures of invariant reactions and other phase transformations were investigated from DTA measurements which were carried out with the rate 1 K min-1. Finally, the experimental results were compared with the isopleths obtained from prediction and calculation of the phase diagram which were done by using CALPHAD method. Experimental data obtained in this work are in good agreement with the results of calculation.

Methyl Trichlorosilane Prepared Methyl Sodium Silicate

2012 ◽  
Vol 184-185 ◽  
pp. 1064-1067
Author(s):  
Guang Xia Zhang ◽  
Qiao Yun Zhang ◽  
Ze Min Chen
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Sodium Hydroxide ◽  
Sodium Silicate ◽  
Water Solubility ◽  
Experimental Results ◽  
White Powder ◽  
Molten State

This paper studied how to prepare Methyl Sodium Silicate from Methyl Trichlorosilane. Methyl trichlorosilane hydrolyzed on the interface of cyclohexane and water, then hydrolysate and sodium hydroxide prepared methyl sodium silicate at molten state. Manufactrue was characterised by XRD, IR, and differential thermal analysis. The experimental results indicate that the best hydrolyze condition was the proportion of methyl trichlorosilane and water was 10~12:100 , at 5°C, lasting for 45min; the best condition of prepared methyl sodium silicate was the proportion of sodium hydroxide and hydrolysate was 2.1~2.3:1, at 300 ~450°C, lasting for 50min. The manufacture was white powder, water-solubility and well stabilization bellow 450°C.

Custom 1-D CFD Numeric Model of Single-Cell Scale Sample Holder for Scanning Thermal Analysis

2012 ◽  
Author(s):  
Logan M. Compton ◽  
James L. Armes ◽  
Gary L. Solbrekken
Keyword(s):  
Thermal Analysis ◽  
Heat Capacity ◽  
Thermodynamic Properties ◽  
Latent Heat ◽  
Thermoelectric Module ◽  
Experimental Results ◽  
Sample Holder ◽  
Current Profile ◽  
Scanning Calorimetry ◽  
Numeric Model

Successful cryopreservation protocols have been developed for a limited number of cell types through an extensive amount of experimentation. To optimize current protocols and to develop effective protocols for a larger range of cells and tissues it is imperative that accurate transport models be developed for the cooling process. Such models are dependent on the thermodynamic properties of intracellular and extracellular solutions, including heat capacity, latent heat, and the physical phase change temperatures. Scanning techniques, such as differential-scanning calorimetry (DSC) and differential thermal analysis are effective tools for measuring those thermodynamic properties. It is essential to understand the behavior of the in house fabricated differential-scanning calorimeter given different cooling and warming rates to reassure and validate the obtained experimental results. A 1-D transient CFD code was created in Matlab using Patankar’s theory to not only validate obtained experimental results but aid in optimizing the control system to produce linear cooling and warming rates. A freezing model was also implemented as a subroutine to numerically observe the effect of heat release and absorption of the sample during a run. The numeric model is composed of a multilayer scheme that incorporates a thermoelectric module which provides the primary temperature control along with the micron sized bridge with sample holder and thermocouple. An electric current profile is imported in from either an experimental run to validate results or from an optimization program to determine the optimum electrical current profile for a desired temperature profile. Numeric detection of heat capacity, latent heat, and thermal resistance has also been demonstrated.

The Silver–Calcium System

1971 ◽  
Vol 49 (8) ◽  
pp. 1315-1316 ◽  
Author(s):  
A. N. Campbell ◽  
W. H. W. Wood
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
High Temperature ◽  
Powder Diffraction ◽  
Composition Range ◽  
X Ray ◽  
Good Agreement

The Ag–Ca system has been reinvestigated over the composition range 50–100 atomic % Ca, by differential thermal analysis and high temperature X-ray powder diffraction. Our results are in good agreement with those of Alexander et al. (1) and those of Pascal et al. (2) in the region 50–59 atomic % Ca, but the peritectic claimed by Alexander et al., lying at 50% Ca and 598 °C, appears not to exist, according to our DTA and X-ray results. Here and elsewhere our results substantiate those of Pascal et al. We also find that the compound AgCa3 is formed peritectically, and not congruently as suggested by Alexander et al.

scholarly journals Thermodynamic calculation of phase equilibria in stainless steels

2012 ◽  
Vol 48 (3) ◽  
pp. 383-390 ◽  
Author(s):  
G. Klancnik ◽  
Steiner Petrovic ◽  
J. Medved
Keyword(s):  
Thermal Analysis ◽  
Heat Capacity ◽  
Stainless Steel ◽  
Stainless Steels ◽  
Melting Behavior ◽  
Calphad Method ◽  
Thermodynamic Calculations ◽  
Thermodynamic Investigation ◽  
Good Agreement ◽  
Alloy Systems

In this paper two examples of thermodynamic investigation of stainless steels using both, experimental and modeling approach are described. The ferritic-austenitic duplex stainless steel and austenitic stainless steel were investigated using thermal analysis. The complex melting behavior was evident for both alloy systems. Experimentally obtained data were compared with the results of the thermodynamic calculations using the CALPHAD method. The equilibrium thermal events were also described by the calculated heat capacity. In spite of the complexity of both selected real alloy systems a relative good agreement was obtained between the thermodynamic calculations and experimental results.

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