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.

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.

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.

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.

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 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.

Étude thermodynamique des trois isomères du dihydroxybenzène

1991 ◽  
Vol 69 (3) ◽  
pp. 481-488 ◽  
Author(s):  
R. Sabbah ◽  
E. N. L. E. Buluku
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Triple Point ◽  
Van Der Waals Interactions ◽  
Enthalpies Of Formation ◽  
Chemical Calculation ◽  
Conjugation Energy ◽  
Heat Capacity Measurements ◽  
Intramolecular Hydrogen ◽  
Enthalpies Of Sublimation

The present work is concerned with a thermodynamic study of the three isomers of dihydroxybenzene. By combustion calorimetry of small amounts of substance, sublimation calorimetry, differential thermal analysis, and heat capacity measurements, it was possible to determine the enthalpies of formation of 1,2-, 1,3-, and 1,4-dihydroxybenzene in the condensed and gaseous phases, their enthalpies of fusion and transition, and the temperature of their triple point and transition. The experimental results are used to discuss the relative stability and determine the conjugation energy of the three compounds. The values are in good agreement with the theoretical values obtained from a quantum chemical calculation. The enthalpies of atomization enabled us to determine an energy value for the intramolecular Cb—OH bond in dihydroxybenzenes and to correlate it with previous results obtained from a study of alkane-diols. The enthalpies of sublimation were discussed. An intramolecular hydrogen bond was displayed in the ortho isomer. Intermolecular hydrogen bonds associated with van der Waals interactions exist in dihydroxybenzenes. Their energy contributions were determined. Key words: thermodynamics, calorimetry, differential thermal analysis, 1,2-benzenediol or 1,2-dihydroxybenzene or catechol; 1,3-benzenediol or 1,3-dihydroxybenzeneorresorcinol; 1,4-benzenediol or 1,4-dihydroxybenzene or hydroquinone or quinol; enthalpies of combustion, of sublimation, of fusion, of transition, energy of conjugation, enthalpies of atomization, of inter- and intramolecular bonds; triple point and transition temperatures.

Intramolecular hydrogen bonds: common motifs, probabilities of formation and implications for supramolecular organization

2000 ◽  
Vol 56 (5) ◽  
pp. 849-856 ◽  
Author(s):  
Clair Bilton ◽  
Frank H. Allen ◽  
Gregory P. Shields ◽  
Judith A. K. Howard
Keyword(s):  
Hydrogen Bond ◽  
Bond Formation ◽  
Intermolecular Hydrogen Bond ◽  
The Other ◽  
Supramolecular Organization ◽  
Intermolecular Bond ◽  
Hydrogen Bond Formation ◽  
Ability To Act ◽  
Structural Database ◽  
Intramolecular Hydrogen

A systematic survey of the Cambridge Structural Database (CSD) has identified all intramolecular hydrogen-bonded ring motifs comprising less than 20 atoms with N and O donors and acceptors. The probabilities of formation Pm of the 50 most common motifs, which chiefly comprise five- and six-membered rings, have been derived by considering the number of intramolecular motifs which could possibly form. The most probable motifs (Pm > 85%) are planar conjugated six-membered rings with a propensity for resonance-assisted hydrogen bonding and these form the shortest contacts, whilst saturated six-membered rings typically have Pm < 10%. The influence of intramolecular-motif formation on intermolecular hydrogen-bond formation has been assessed for a planar conjugated model substructure, showing that a donor-H is considerably less likely to form an intermolecular bond if it forms an intramolecular one. On the other hand, the involvement of a carbonyl acceptor in an intramolecular bond does not significantly affect its ability to act as an intermolecular acceptor and thus carbonyl acceptors display a substantially higher inclination for bifurcation if one hydrogen bond is intramolecular.

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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