Die Schmelzenthalpie des Benzils und 4-Nitrophenols

Booß, Hans-Jürgen; Hauschildt, K.-R.

doi:10.1007/bf00430787

Cited by 13 publications

(5 citation statements)

References 8 publications

(3 reference statements)

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“…Benzil was examined in a control experiment since it is a 14-carbon α-diketone just like di- tert -butyl- o -benzoquinone ( 5 ) and its thermochemistry previously has been reported. Our measured standard molar enthalpy of formation in the solid phase is −39.41 ± 0.79 kcal mol -1 , which is very nearly the average of the two most contemporaneous values in the literature (i.e., −42.8 ± 1.0 and −36.8 ± 1.0 kcal mol -1 ). , Likewise, our measured fusion and sublimation enthalpies at 298 K (5.468 ± 0.047 and 25.41 ± 0.67 kcal mol -1 , respectively) also are in good accord with earlier measurements of 5.423 and 23.5 kcal mol -1 (no uncertainties given) at a mean temperature of 329 K. , Consequently, calorimetric experiments were carried out on 5 since o -benzoquinone is too reactive and unstable to carry out a direct determination of its enthalpy of formation via combustion calorimetry.…”

Section: Resultssupporting

confidence: 90%

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

et al. 2005

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Radical anions of o-, m-, and p-benzoquinone were produced in a Fourier transform mass spectrometer by low energy electron attachment or collision-induced dissociation and were differentiated. Classical derivatization experiments also were carried out to authenticate the ortho and meta anions. Gas-phase techniques were used to measure the proton affinities of all three radical anions and the electron affinities of o- and m-benzoquinone. By combining these results in thermodynamic cycles, we derived heats of hydrogenation of o-, m-, and p-benzoquinone (Delta(hyd)H degrees (1o, 1m, and 1p) = 42.8 +/- 4.1, 74.8 +/- 4.1, and 38.5 +/- 3.0 kcal mol(-)(1), respectively) and their heats of formation (Delta(f)H degrees (1o, 1m, and 1p) = -23.1 +/- 4.1, 6.8 +/- 4.1, and -27.7 +/- 3.0 kcal mol(-)(1), respectively). Good accord with the literature value for the para derivative was obtained. Combustion calorimetry and heats of sublimation also were measured for benzil and 3,5-di-tert-butyl-o-benzoquinone. The former heat of formation agreed with previous determinations, while the latter result (Delta(f)H degrees (g) = -73.09 +/- 0.87 kcal mol(-)(1)) was transformed to Delta(f)H degrees (1o) = -18.9 +/- 2.2 kcal mol(-)(1) by removing the effect of the tert-butyl groups via isodesmic reactions. This led to a final value of Delta(f)H degrees (1o) = -21.0 +/- 3.1 kcal mol(-)(1). Additivity was found to work well for m-benzoquinone, but BDE1 and BDE2 for 1,2- and 1,4-dihydroxybenzene differed by a remarkably small 14.1 +/- 4.2 and 23.5 +/- 3.7 kcal mol(-)(1), respectively, indicating that o- and p-benzoquinone should be excellent radical traps.

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Section: Resultssupporting

confidence: 90%

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

et al. 2005

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“…The 3% difference may not seem to amount to much, but it is quite sufficient to account at least qualitatively for the melting-point differences. Heat and entropy of fusion are available for the 1,4-isomer: DH f 18.05 kJ mol À1 , DS f 55.3 J mol À1 K À1 [27]. Corresponding values for the other two isomers are unfortunately not available; to estimate these quantities from the above data, we would require a knowledge of the heat capacities of the solid and liquid phases for all three isomers, which we do not have.…”

mentioning

confidence: 99%

Solid-State Behaviour of the Dichlorobenzenes: Actual, Semi-Virtual and Virtual Crystallography

Boese

Kirchner

Dunitz

et al. 2001

HCA

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For Edgar, a teacher whose influence will never stop The crystal structures of the low-melting 1,2-and 1,3-dichlorobenzene isomers have been determined by Xray analysis and in situ crystallisation techniques. Attempts to predict these structures in advance by force-field calculations were not successful, although the known crystal structures of two of the three polymorphs of the 1,4-isomer were successfully a posteriori predicted. Calculated lattice energies were supplemented with estimated lattice-vibrational entropies obtained in the rigid-body approximation. Energy calculations for actual and virtual crystal structures indicate that the higher melting point of the 1,4-isomer can be largely attributed to more efficient crystal packing.

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“…The enthalpies of fusion (DH m ) of BZL and MNA are determined to be 108.27 J g À1 and 167.22 J g À1 , respectively, giving the entropies of fusion, DS m , to be 61.58 J (mol K) À1 and 60.05 J (mol K) À1 , in excellent agreement with the reported results, 61.65 J (mol K) À1 and 61.3 J (mol K) À1 . 47 This suggests that no oxidation occurs during the DSC measurements for the pure MNA. The FT-IR results also reveal the same absorption peaks of the -NH 2 and -NO 2 groups for the mixtures at the eutectic composition before and after DSC measurements as those in the FT-IR spectrum of the pure MNA.…”

Section: Resultsmentioning

confidence: 93%

Glass transition and mixing thermodynamics of a binary eutectic system

Chen

Gao

et al. 2014

Phys. Chem. Chem. Phys.

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A quantitative evaluation of the contribution of mixing thermodynamics to glass transition is performed for a binary eutectic benzil and m-nitroaniline system. The microcalorimetric measurements of the enthalpy of mixing give small and positive values, typically ~200 J mol(-1) for the equimolar mixture. The composition dependence of the glass transition temperature, T(g), is found to show a large and negative deviation from the ideal mixing rule. The Gordon-Taylor and Couchman-Karasz models are subsequently applied to interpret the T(g) behavior, however, only a small fraction of the deviation is explained. The analyses of the experimental results manifest quantitatively the importance of the mixing thermodynamics in the glass transition in miscible systems.

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Die Schmelzenthalpie des Benzils und 4-Nitrophenols

Abstract: Von allen wurde der Schmelzpunkt mit dem Schmelzpunktbestimmungsger~t l~p 1, Mettler, kontrolliert und ~bereinstimmung mit dem Literaturwert innerhalb einer Abweichung yon 0,05--0,1 ~ gefunden; nur bei 1,4-Dichlorbenzol betrug die Abweichung + 0,3 ~ In Tab.

Cited by 13 publications

References 8 publications

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

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

Solid-State Behaviour of the Dichlorobenzenes: Actual, Semi-Virtual and Virtual Crystallography

Glass transition and mixing thermodynamics of a binary eutectic system

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