Vapor formation enthalpy

This is the solvent and vaporization-corrected enthalpy of hydrogenation of the diene from Reference 23. There is no need in the current context for the enthalpy of formation of the hydrogenation product 2,3-di-f-butylbutane (or more properly named 2,2,3,4,5,5-hexamethylhexane), unlisted in our archives, and derived in Reference 23 by molecular mechanics. 

Thermochemical attention in this chapter is directed towards compounds with carbon—zinc bonds, i.e. species that are usually labeled organometallic. The thermodynamic properties that we discuss are restricted to the enthalpy of formation (often called the heat of formation ), enthalpy of vaporization and carbon—zinc bond energies. We forego discussion of other thermochemical properties such as entropy, heat capacity or excess enthalpy. The energy units are kJmoU where 4.184 kJ is defined to equal 1 kcal. 

Screttas, C.G., and M. Micha-Screttas. 1991. Some properties and trends of enthalpies of vaporization and of Trouton s ratios of organic compounds. Correlation of enthalpies of vaporization and enthalpies of formation with normal boiling points. /. Org. Chem. 56 1615-22. 

Enthalpies of formation are from A. M. Rozhnov and T. N. Nesterova, Russ. J. Phys. Chem., 27, 1390 (1973). The dibromobutane gas-phase enthalpies were obtained from liquid-phase isomerization of the 1,2-species and semiempirical corrections to the 1,4-dibromobutane enthalpy of vaporization. The enthalpies of formation are (kJmol1) 1,2-dibromobutane [(1), -140 8 (g),-92.9]. 

The enthalpies of vaporization and formation of halogenide for 2-chloro-l,3,2-dioxarsinane 63 have been determined. The formation enthalpy of the compound in the condensed and gaseous phases has also been calculated <1996PS97>. 

An investigation of the thermodynamic properties of the series of lactones of ring size 5-14 has been conducted. The enthalpies of formation, enthalpies of hydrolysis, enthalpies of reduction to the diol, enthalpies of vaporization, and strain energies of these lactones were determined. Caprylolactone (13) was found to be among the most strained of the lactones examined. The experimentally determined heat of formation of caprylolactone was compared with that calculated using the MM3 force field (unoptimized at the time for esters), and the results were useful for refining the MM3 parameters <91JA7697>. 

The vapor generated by flash distillation has a higher enthalpy than the liquid. The energy demand of the vapor formation is covered by a temperatrrre decrease of the whole system. From (5.1-41) follows ... 

Because the calorimetric methods of measurement of enthalpy of vapor formation are very difficult, the indirect mefliods are used, especially for less volatile substances. The application of generalized expression of the first and second laws of thermodynamics to the heterogeneous equilibrium between a condensed phase in isobaric- thermal conditions is given in the Clausius-Clapeyron equation that relates enthalpy of a vapor formation at the vapor pressure, P, and temperature, T. For one component system, the Clausius-Clapeyron equation has the form ... 

The authors discuss experimental methods used to measure and derive enthalpies of polymerization. A listing of experimental data on enthalpies of polymerization is provided for 81 organic polymerization reactions. Other tables give enthalpies.of formation, enthalpies of vaporization, entropies, Gibbs... 

This monograph is a summary and a consolidation of the results of some years of work by Tatevskii and others, extending and elaborating some procedures introduced by Rossini and others. Properties calculated include molar volume, molar refraction, vapor pressure, enthalpy of formation from atoms or eiements, Gibbs energy of formation, and enthalpy of combustion. Three different methods are used. Tables of constants and illustrations of the accuracy of the methods are given. 

The thermochemistry and thermal effects of reactions involving dithio-phosphoric acids have been analyzed and the formation enthalpies of a series of dithiophosphates determined. Analysis of the resulting experimental data was carried out on the basis of an additive scheme. Group contributions into the vaporization and formation enthalpies were determined and thermochemical characteristics of the compounds were calculated. 

Heat Capacity of Selected Solids, 12-200 Heat Capacity of the Elements at 25 C, 4-135 Heat conductivity see Thermal conductivity Heat of Combustion, 5-70 Heat of dilution see Enthalpy of dilution Heat of formation see Enthalpy of formation Heat of fusion see Enthalpy of fusion Heat of solution see Enthalpy of solution Heat of vaporization see Enthalpy of vaporization Hebrew alphabet, 2-36 Helium see also Elements... 

In pure metals, empirical relationships have been noted between the monovacancy formation enthalpy and dtho-the heat of vaporization, the Debye temperature, or the electron density at the boundary of an atomic cell (Miedema, 1979). In particular, the analogy with a macroscopic hole has suggested the fairly accurate Miedema relationship... 

Molecular Nature of Steam. The molecular stmcture of steam is not as weU known as that of ice or water. During the water—steam phase change, rotation of molecules and vibration of atoms within the water molecules do not change considerably, but translation movement increases, accounting for the volume increase when water is evaporated at subcritical pressures. There are indications that even in the steam phase some H2O molecules are associated in small clusters of two or more molecules (4). Values for the dimerization enthalpy and entropy of water have been deterrnined from measurements of the pressure dependence of the thermal conductivity of water vapor at 358—386 K (85—112°C) and 13.3—133.3 kPa (100—1000 torr). These measurements yield the estimated upper limits of equiUbrium constants, for cluster formation in steam, where n is the number of molecules in a cluster. 

An overview of some basic mathematical techniques for data correlation is to be found herein together with background on several types of physical property correlating techniques and a road map for the use of selected methods. Methods are presented for the correlation of observed experimental data to physical properties such as critical properties, normal boiling point, molar volume, vapor pressure, heats of vaporization and fusion, heat capacity, surface tension, viscosity, thermal conductivity, acentric factor, flammability limits, enthalpy of formation, Gibbs energy, entropy, activity coefficients, Henry s constant, octanol—water partition coefficients, diffusion coefficients, virial coefficients, chemical reactivity, and toxicological parameters. 

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