Thermodynamic Data and Structures

The choice of a given database as source of auxiliary values may not be straightforward, even for a thermochemist. Consistency is a very important criterion, but factors such as the publication year, the assignment of an uncertainty to each value, and even the scientific reputation of the authors or the origin of the database matter. For instance, it would not be sensible to use the old NBS Circular 500 [22] when the NBS Tables of Chemical Thermodynamic Properties [17], published in 1982, is available. If we need a value for the standard enthalpy of formation of an organic compound, such as ethanol, we will probably prefer Pedley s Thermodynamic Data and Structures of Organic Compounds [15], published in 1994, which reports the error bars. Finally, if we are looking for the standard enthalpy of formation of any particular substance, we should first check whether it is included in CODATA Key Values for Thermodynamics [16] or in the very recent Active Thermochemical Tables [23,24],... 

J. B. Pedley. Thermodynamic Data and Structures of Organic Compounds. Thermodynamics Research Center Data Series, vol. 1 Thermodynamics Research Center College Station, 1994. 

Pedley JB (1994) Thermodynamical data and structures of organic compound, vol 1. TRC Data Series, Boca Raton, FL... 

The reactivity of chromium(V) and chromium(IV) species is uncertain since there are no reliable thermodynamic data, and not much can be said at present about the structure of these species. With respect to the latter some hints can be obtained from the fact that the changeover from chromium(V) to chromium(IV) or vice versa in all cases was found to be rate determining, which seems to correlate well with the conclusion of Tong and King d that Cr(VI) and Cr(V) have coordination number four, whereas Cr(IV) and Cr(III) have six. 

The primary source of information for enthalpies of formation is J. B. Pedley, R. D. Naylor and S. P. Kirby, Thermochemical Data of Organic Compounds (2nd Ed.), Chapman Hall, New York, 1986. The successor to this volume, J. B. Pedley, Thermochemical Data and Structures of Organic Compounds, Vol. I, Thermodynamics Research Center, College Station, Texas, USA, 1994, has recently been published. We have used values from this latter source when the compounds were not included in the earlier edition. In any case, no reference citation is given except for occasionally referring to either volume as Pedley or merely archival . Where data were... 

J. B. Pedley, R. D. Naylor and S. P. Kirby, Thermochemical Data of Organic Compounds (2nd edn.), Chapman Hall, New York, 1986 J. B. Pedley, Thermochemical Data and Structures of Organic Compounds, Volume 1, Thermodynamics Research Center, College Station, 1994. 

Pedley JB (1994) Thermochemical data and structures of organic compounds. Thermodynamics Research Center, College Station, TX... 

A number of force fields used in organic chemistry have been fitted to thermodynamic data, and most force fields used in inorganic chemistry are based on these. Also, initial guesses for parameters are often based on spectroscopic force constants and therefore related to physically meaningful parameters. Thus, in many cases, reasonably accurate thermodynamic data can be obtained with force fields where parts were fitted to structural data165,66. ... 

The physics of electrostatics in aqueous solution has attracted scientists notice for centuries. At present, the solvation of ions, volumes and radii of ions in solution, and ionic interactions are still hotly debated research fields. Recently, thermodynamic, transport and structural data were mutually employed for gaining fruitful physicochemical insights into electrolyte solutions [2]. This chapter recapitulates the essential... 

This is clearly an area where the combination of thermodynamic, kinetic and structural information potentially can lead to successful strategies for controlling the polymorphic form obtained, in specific instances a metastable form, and as the means for obtaining these data become more sophisticated the approaches described here are sure to be developed and expanded (see also Section 3.7). 

The thermal stability of compounds is able to be evaluated by discussion based on the thermodynamic data and/or the electronic structures. As for the search of new materials, one can get information on the electronic structure using either the molecular orbital or the band calculations, though the thermodynamic data may not be obtainable in some cases. 

The calculation depends on many molecular parameters, which are estimated from a combination of experimental bulk thermodynamic data and molecular structure calculations, employing both molecular and quantum mechanics. The model semiquantitatively reproduces water absorption, polymer density, and the number of water molecules per exchange site in these polymers. For a comprehensive description of this work, see References 60, 91, and 92. 

A pseudo-quantitative application of the theoretical formalism has been made for Nafion. The values for the requisite molecular parameters were estimated from a combination of experimental bulk thermodynamic data and molecular structure calculations using both molecular and quantum mechanics (23,24). A constraint was imposed in the development of the structural formalism. The model was constructed so that the predicted structural information could be used in a computer simulation of ion transport through an ionomer, that is, modeling the ionomer as a permselective membrane. 

The thermodynamic, kinetic and structural data presented above give some indications about the folding pathway required to form G-quadruplexes. In terms of folding intermediates, the best-studied systems concern tetramolecular quadruplexes. Several experimental and theoretical studies provide clues on the possible ways to a fully formed quadruplex. 

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