Thermodynamics trends

I think this would provide at least a partial explanation of some of these different trends. For example, the large rate increase with Co(CN)fi 3 as reductant in going from Co(NH3)6Ff2 through to Co(NH3)6Br+2 is in line with the favored thermodynamic trend with respect to the stability of both the bond being broken and that being formed. 

DSC analysis represents a superior method of thermal analysis, in that the area under a DSC peak is directly proportional to the heat absorbed or evolved by the thermal event, and integration of these peak areas yields the enthalpy of reaction (in units of calor-ies/gram or Joules/gram). Even though conclusions reached on the basis of enthalpies of fusion are possibly compromised by their omission of the entropy contribution, an indication of the thermodynamic trends inherent in the system is often possible. For instance, the same polymorphic form of moricizine hydrochloride was deduced on the basis of thermal analysis and equilibrium solubility measurements. On the other hand, auranofin represents a compound for which one anhydrous polymorphic form is predicted to be the most stable by virtue of its melting point and heat of fusion but for which solubility measurements demonstrate that the other polymorph was in fact the thermodynamically stable form. ... 

In conclusion, the general thermodynamic trends in the isomerization of bicyclic olefins have been outlined, but the detailed mechanisms of these acid-catalyzed reactions require further investigation. 

On the basis of the most recent and most complete data set [985], the thermodynamics of the dissociation reaction equation (15.3) strongly favour the right-hand side of the equation [1764]. The thermodynamic trends in dissociation of the carbonyl dihalide series of symmetrical compounds are shown in Table 15.3. 

Semiempirical calculations of free energies and enthalpies of hydration derived from an electrostatic model of ions with a noble gas structure have been applied to the ter-valent actinide ions. A primary hydration number for the actinides was determined by correlating the experimental enthalpy data for plutonium(iii) with the model. The thermodynamic data for actinide metals and their oxides from thorium to curium has been assessed. The thermodynamic data for the substoicheiometric dioxides at high temperatures has been used to consider the relative stabilities of valence states lower than four and subsequently examine the stability requirements for the sesquioxides and monoxides. Sequential thermodynamic trends in the gaseous metals, monoxides, and dioxides were examined and compared with those of the lanthanides. A study of the rates of actinide oxidation-reduction reactions showed that, contrary to previous reports, the Marcus equation ... 

Thermodynamic Trend Methanation much favored against FT-Synthesis... 

Greeley J, Norskov JK (2007) Electrochemical dissolution of surface alloys in acids thermodynamic trends from first-principles calculations. Electrochim Acta 52 5829—5836... 

In addition to the convincing success of first-principles computations in predicting more active catalyst compositions and morphologies, the important challenge associated with the chemical stability in the reaction environment of the catalyst has been pointed out [7, 24, 104]. ORR occurs in aqueous electrochemical environment and at high potentials where both metal dissolution and surface oxidation of catalyst may become favorable. The thermodynamic trends for electrochemical dissolution of surface alloys in acids from first-principles calculation have been reported by Greeley and Norskov [105]. The dissolution potentials for solute metal atoms in the surface layer of host metal are calculated. Correlation between the... 

This monograph contains a general discussion of the methodology, kinetics, mechanisms, structural features, and general thermodynamic trends of ionic association reactions in solution. In the Appendix there are several tables of thermodynamic functions for ion-association reactions with references to the source literature. 

Mathematical Consistency Requirements. Theoretical equations provide a method by which a data set s internal consistency can be tested or missing data can be derived from known values of related properties. The abiUty of data to fit a proven model may also provide insight into whether that data behaves correctiy and follows expected trends. For example, poor fit of vapor pressure versus temperature data to a generally accepted correlating equation could indicate systematic data error or bias. A simple sermlogarithmic form, (eg, the Antoine equation, eq. 8), has been shown to apply to most organic Hquids, so substantial deviation from this model might indicate a problem. Many other simple thermodynamics relations can provide useful data tests (1—5,18,21). 

Turbine-Blade Cooling The turbine inlet temperatures of gas turbines have increased considerably over the past years and will continue to do so. This trend has been made possible by advancement in materials and technology, and the use of advanced turbine bladecooling techniques. The olade metal temperature must be kept below 1400° F (760° C) to avoid hot corrosion problems. To achieve this cooling air is bled from the compressor and is directed to the stator, the rotor, and other parts of the turbine rotor and casing to provide adequate cooling. The effect of the coolant on the aerodynamic, and thermodynamics depends on the type of cooling involved, the temperature of the coolant compared to the mainstream temperature, the location and direction of coolant injection, and the amount of coolant. 

The basic thermodynamic data for the design of such reactions can be used to assess the dissociation energies for various degrees of dissociation, and to calculate, approximately, tire relevant equilibrium constants. One important source of dissociation is by heating molecules to elevated temperamres. The data below show the general trend in the thermal dissociation energies of a number of important gaseous molecules. 

The above data are correct to about 20 kJ mole but it will be seen that the general trend among these more covalent bonds does appear to be a decrease in stability from carbon to silicon, i.e. the same way as was found for more ionic bonds in the halides. Thermodynamic data for metallorganic methyl compounds used in the produchon of semiconductor systems are shown in Table 2.3. 

The thermodynamic and other physical properties of binary oxides (e.g. A//f, AGf, mp, etc.) show characteristic trends and variations when plotted as a function of atomic number, and the preparation of such plots using readily available compilations of data can be a revealing and rewarding exercise. 

Trends in chemical reactivity are also apparent, e.g. ease of hydrolysis tends to increase from the non-hydrolysing predominantly ionic halides, through the intermediate halides to the readily hydrolysable molecular halides. Reactivity depends both on the relative energies of M-X and M-0 bonds and also, frequently, on kinetic factors which may hinder or even prevent the occurrence of thermodynamically favourable reactions. Further trends become apparent within the various groups of halides and are discussed at appropriate points throughout the text. 

These values should be compared with those for the other halogens (in 1 M acid) (p. 854). Noteworthy features are that At is the only halogen with an oxidation state between 0 and V that is thermodynamically stable towards disproportionation, and that the smooth trends in the values of E°( X2/X ) and (HOX/jXi) continue to At. 

Various /-alkoxy radicals may be formed by processes analogous to those described for /-butoxy radicals. The data available suggest that their propensities for addition vs abstraction are similar.72 However, rate constants for [3-scission of /-alkoxy radicals show marked dependence on the nature of substituents a to oxygen (Figure 3.6).210 420,421 Polar, steric and thermodynamic factors are all thought to play a part in favoring this trend.393... 

Equilibrium vapor pressures were measured in this study by means of a mass spectrometer/target collection apparatus. Analysis of the temperature dependence of the pressure of each intermetallic yielded heats and entropies of sublimation. Combination of these measured values with corresponding parameters for sublimation of elemental Pu enabled calculation of thermodynamic properties of formation of each condensed phase. Previ ly reported results on the subornation of the PuRu phase and the Pu-Pt and Pu-Ru systems are correlated with current research on the PuOs and Pulr compounds. Thermodynamic properties determined for these Pu-intermetallics are compared to analogous parameters of other actinide compounds in order to establish bonding trends and to test theoretical predictions. 

It would be interesting to further examine the vaporization of Pu-intermetallics at higher temperatures in order to search for molecular vapor species involving Pu and the noble metals. Due to the directional nature of 5f electrons in Pu, they may not be involved in the bonding of the solid intermetallics, but could contribute to the stability of a gas phase molecule. Additional measurements of the thermodynamic stabilities of Np- and Am-noble metal intermetallics corresponding to the Pu phases considered in this work would also assist in establishing bonding trends. 

All of the information obtained in this research area depends upon indirect evidence through the use of nonisotopic carriers or normalized data in the form of ratios. These are subject to error but the trends and insights that have been obtained are very useful to the description of the behavior of plutonium in the environment. Better thermodynamic data in the range of environmental concentrations would be helpful in further quantification of chemical species, as would phenomenalogical descriptions of the behavior of plutonium in reasonably good models of the environment. 

A major goal was to investigate the solid state structures of such compounds by single crystal X-ray diffraction. It was found that Lewis acid-base adducts R3M—ER3 show general structural trends, which allow estimations on the relative stability of the adducts. The experimental results were confirmed by computational calculations, giving even deeper insights into the structural parameters and the thermodynamic stability of simple Lewis acid-base adducts. In addition, their thermodynamic stability in solution was investigated by temperature-dependent NMR spectroscopy. 

Reliable information on the thermodynamic stability of group 13/15 adducts is usually obtained by gas phase measurements. However, due to the lability of stibine and bismuthine adducts in the gas phase toward dissociation, temperature-dependent H-NMR studies are also useful for the determination of their dissociation enthalpies in solution [41b], We focussed on analogously substituted adducts t-BusAl—E(f-Pr)3 (E = P 9, As 10, Sb 11, Bi 12) since they have been fully characterized by single crystal X-ray diffraction, allowing comparisons of their thermodynamic stability in solution with structural trends as found in their solid state structures. 

The nonnuclear chemistry of Fr reduces to studies of coprecipitation in which Fr shows the behavior of the heavier alkali metal. Coprecipitation is followed by ion exchange to concentrate Fr Physical (mp, density, crystal parameters) and chemical (thermodynamics, solvation entropies) properties are theoretically derived or extrapolated from the trends exhibited by the other alkali metals. 

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