Thermodynamic properties of organic compounds

By employing calorimetric and cryometric methods, the melting total and the premelting enthalpies of stearic acid were measured and the phase diagrams of the solid-liquid equilibria stearic acid +A (whereA is an aromatic compound or a dicarboxylic acid or I₂) were determined.

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Zusammenfassung Die Gesamt-Schmelz-Enthalpie und die Vor-Schmelz-Enthalpie der Stearinsäure werden unter Anwendung kalorimetrischer und kryometrischer Methoden gemessen und die Phasendiagramme der festflüssigen Gleichgewichte von Stearinsäure+A (wobeiA eine aromatische Verbindung oder eine Dicarbonsäure oder I₂ ist) bestimmt.

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Résumé Mesure de l'enthalpie totale de fusion de l'acide stéarique, ainsi que de celle de pré-fusion, par calorimétrie et cryométrie. Etablissement des diagrammes de phases pour les équilibres solide-liquide du système acide stéarique +A;A désignant un composé aromatique ou un acide dicarboxylique ou I[in2].

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- + ( . I₂).

     

Thermodynamic properties of organic compounds

Journal of Thermal Analysis and Calorimetry - Calorimetric and cryometric methods were employed to measure the enthalpy and entropy of fusion of caprylamide and stearamide.     

Thermodynamic properties of organic oxygen compounds 42. Physical and thermodynamic properties of benzaldehyde

The following properties of a purified sample of benzaldehyde have been measured: vapour pressure (311 to 481 K); density of liquid (293 to 490 K); heat capacity of crystals and liquid (13 to 425 K); enthalpy of fusion; triple-point, normal boiling, and critical temperatures; and enthalpy of combustion in oxygen. From the measurements, the enthalpy of vaporization, the entropy (crystal, liquid, and ideal gas); and the enthalpy of formation (liquid and ideal gas) have been calculated. Thermodynamic functions (0 to 1000 K) of the ideal gas have been calculated from a vibrational assignment and molecular dimensions.     

Thermodynamic properties of lanthanum(III) and holmium(III) hydroxo compounds

Conductometric and potentiometric titration experiments were performed to determine the pH values of hydroxo compound formation in solutions of lanthanum(III) and holmium(III) nitrates. The instability constants of monohydroxo complexes, the solubility product constants of hydroxides, and the Gibbs energies of formation of the corresponding compounds are calculated.     

Thermodynamic properties of oxygen compounds I. Vinyl acetate

A complete vibrational assignment is made and ideal gas thermodynamic properties of vinyl acetate have been reported from 100–1500 K. Internal rotational contributions have been calculated using Pitzer and Gwinn's tables.     

Thermodynamic properties of organic compounds IV. Miscibility gaps in mixtures of o-terphenyl + aliphatic dicarboxylic acid

Miscibility gaps, critical solution temperatures, and critical compositions for mixtures of C₅ to C₉ aliphatic dicarboxylic acids with o-terphenyl are reported.     

Thermodynamic studies on iodine(III) compounds

The standard enthalpies of aqueous hydrolysis of I₂Cl₆(c) and I₂(CH₃COO)₆(c) have been determined as −59.3 ± 3.4 and −57.1 ± 2.0 kJ mol⁻¹, respectively, leading to the estimates of the standard enthalpies of formation {ΔH^⊖_f[I₂Cl₆(c)] = −179.8 ± 4.0 and ΔH^⊖_f [I₂(CH₃COO)₆(c)] = −2101.6 ± 9.0 kJ mol⁻¹, respectively}. A thermometric titration of I₂Cl₆ with aqueous AgNO₃ has been used to investigate the mechanismof the hydrolysis reaction.     

Partial molar volumes of organic compounds in water. III. Carbohydrates

Partial molar volumes in water at 25°C have been determined for a number of carbohydrates, including mono-, di-, tri-, tetra-, penta-, hexa-, hepta-, and polysaccharides and their derivatives. The experimental values can be calculated from the van der Waals volumes of the molecules if account is taken of the shrinkage in volume caused by hydrogen-bonding of solvent molecules to the hydroxyl groups of the sugars.     

Thermodynamic and crystallographic properties of REPd intermetallic compounds

REPd phases have been extensively studied both by thermal, crystallographic, thermodynamic and micrographic methods. As a result of this investigation a possible sequence of structures is proposed which is correlated with the thermal and thermodynamic data.Europium is a divalent rare earth in EuPd while ytterbium in YbPd seems to be present with certain, fixed percentage of atoms in the trivalent state.     

Thermodynamic properties of organic compounds in aqueous solution. II. Apparent molal heat capacities of piperidines,morpholines, and piperazines

Apparent molal heat capacities of some piperidine, morpholine, and piperazine derivatives in aqueous solution have been determined by adiabatic calorimetry in the temperature range 20–55°C and in the molality range 0.2–1m. Comparison of experimental values with those calculated through group contributions, found for monofunctional compounds, indicates strong interactions between the hydrophilic centers. An interpretation is given of the possible mechanism of this interaction. Also, values of ΔC _p for the addition reaction of proton to nitrogen centers of mono- and bifunctional organic compounds are examined.     

Computerized technique in organic microelemental analysis III. Automatic determination of fluorine in organic compounds

The automatic and computerized rapid microanalytical determination of fluorine in organic and organometallic compounds is an easily reproducible procedure. The procedure consists of the combustion of the compound in an empty tube; transfer of the combustion products to the titration vessel by automatic wash; and, finally, colorostatic titration of HF with Th(ClO₄), against alizarin red S.The entire analysis and preparation of the equipment for the next determination are programmed in the time of the 6-min cycle.The analyzer is interfaced to the departmental real-time time-sharing computer, along with electronic microbalances and other analyzers, as a part of the microanalytical laboratory computer service.Results of the analyses are reported on CR terminals and are also stored on the magnetic disk for further processing.     

Optical crystallographic properties of organic compounds

Summary The optical crystallographic properties of coumarin (I), salicylanilide, chlorothymol, and neocinchophen, all used in medicine or related fields, have been determined. These constants are useful in the identification of these compounds. It has been shown that both, chlorothymol and thymol, can be identified in mixtures of these two substances. Salicylanilide shows very strong negative birefringence, whereas coumarin and chlorothymol both show strong and moderately strong positive birefringence, respectively.

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Zusammenfassung Die kristalloptischen Eigenschaften von Cumarin (I), Salioylanilid, Chlorthymol und Neocinchophen, vier Verbindungen, die medizinisch von Interesse sind, wurden bestimmt. Die optischen Konstanten sind für die Erkennung dieser Substanzen nützlich und es wird darauf hingewiesen, daß Chlorthymol und Thymol in Mischungen dieser beiden Verbindungen erkannt werden können. Salicylanilid zeigt sehr starke negative Doppelbrechung, während Cumarin (I) und Chlorthymol stark bzw. mittelmäßig stark positiv doppelbrechend sind.

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Résumé On a déterminé les propriétés cristallographiques optiques de la coumarine (I), de la salicylanilide, du chlorothymol et du néocinchophène, produits employés en médecine. Ces constantes sont utiles pour l'identification de 764 R. N. Castle: Optical Crystallographic Properties of Organic Compounds. ces composés. On a montré que le thymol et le chlorothymol peuvent être identifiés dans les mélanges contenant ces deux substances. La salicylanilide possède une biréfringence négative très forte, tandis que la coumarine et le chlorothymol possèdent respectivement, une biréfringence positive forte et moyenne.

     

Thermodynamic properties of molecular organic crystals containing nitrogen,oxygen and sulfur. III. Molar heat capacities measured by differential scanning calorimetry

In this paper we report on the heat capacities of 18 organic compounds, which form molecular crystals, in the temperature interval 300–450 K. The measurements are performed using DSC technique.     

Thermodynamic properties of spin crossover 3d-metal coordination compounds

Thermodynamic studies are necessary to understand the mechanism of such an interesting phenomenon as spin crossover in complex compounds. A number of reviews have already covered spin crossover in mononuclear complexes, so the suggested review considers in more detail the problems of obtaining thermodynamic data for polynuclear complex compounds of iron (II) with 4-substituted 1,2,4-triazole derivatives. The composition of trinuclear and polynuclear complexes of iron (II) with 1,2,4-triazoles was studied in terms of its effect on C _p(T) dependence; magnetochemical and thermodynamic data are also confronted with each other.     

Relative energy of organic compounds III. Components of the heat of reactions

The relative enthalpies of organic compounds described in Parts I and II of this series made possible to show the contribution of the reactants and products to the heat of reactions. First, the meaning of the relative enthalpies is demonstrated. The components of the heats of reactions are exemplified by a series of reactions: formation of alkyl halides, esters, amides, acid halides, and anhydrides. Further examples are hydrogenation of alkenes, alkynes, benzene, ethylene oxide, aldehydes, and nitriles, and addition of chlorine, water, and hydrogen chloride to ethylene. Acetal and hemiacetal formations and cyclization reactions are also among the examples.     

Thermodynamic and conformational properties of polystyrene. III. Dilute solution studies on branched polymers

Light-scattering and viscometric measurements on dilute solutions of five branched polystyrene polymers are reported. The data include studies in decalin as a function of temperature, including the theta temperature, and in toluene. The results for the radius of gyration and the second virial coefficient are not in accord with the two parameter random-flight model. Possible causes of this descrepancy are considered. It is shown that the intrinsic viscosity of branched chains is not uniquely determined by the radius of gyration.     

Inclusion properties of volatile organic compounds in a calixarene-based organic zeolite

The inclusion properties of a calixarene-based porous material have been studied to investigate the adsorption and the desorption of carbon tetrachloride, chloroform, and water in the zeolite-like structure. Uptake and release processes have been studied both by time-resolved powder X-ray diffraction and by thermogravimetric analysis to obtain structural and kinetic information. The selected guests are able to enter the structure with an increase in the host cell volume and with time-dependent diffusivity coefficients. Chloroform molecules act as a permanent porosity switch promoting a phase transition to non-porous triclinic form.