Thermochemical data sources

In order to calculate polynomial coefficients, the thermodynamic and thermochemical property values must be found in tables or calculated from molecular properties by the methods of statistical thermodynamics. The available tables will be described in the following section. 

A popular and often quoted source is the JANAF Thermochemical Tables (1971), prepared by a team of thermodynamicists at the Dow Chemical Company headed by D. R. Stull and M. W. Chase. This source has thermochemical values for small, mostly inorganic molecules, radicals, and ions up to 6000 K. The calculations are mainly done using the rigid rotator 

Most of the JANAF tables have been fitted to polynomials by the NASA thermodynamics group. Polynomial coefficients for the species included in the main JANAF volume (1971) have been published (Gordon and McBride, 1971) and are supplied with the NASA SP-273 computer program. 

A second source comparable to the JANAF tables published in the Soviet Union by Gurvitch et al. (1967) is not well known in the Western hemisphere. Gurvitch et al. published with their tables a set of nine-term polynomials that cover the temperature range 0-5000 K. This set of polynomials was reprinted in a later publication of Alemasov et al. (1974). Unfortunately, the explanation of how to use these polynomials is not clear, making their use guesswork. 

Most of these drawbacks were corrected by Stull, Westrum, and Sinke (1969). In a regular-size volume the authors have included the ideal gas thermodynamic functions of the API Project 44 as well as others that were not 

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Sources of thermochemical data for such calculations are Vol 7, H38 Lff Heat Effects — Data for Common Explosives NBS Circular 500 (Ref 39a) Cox Pilcher (Ref 89) and the studies of Rhodes Nelson (Ref 24b) and McKinley Brown (Ref 28a) on mixed acids As an example of such a calculation we will compute the heat evolution and temp rise occurring during the mixed acid nitration of glycerol to NG. We will assume that a typical 50/50 nitric acid/sulfuric acid MA is used and that the MA/glycerol ratio is 5/1. Further assumptions are that all the glycerol is converted to NG, and that the heats of soln of NG in die. spent acid, and of spent acid in the NG, are negligibly small (cf discussion of these effects by the writer in Ref 51). The net reaction is then ... 

The thermochemical data for the sulfoxides, sulfones, sulfites and sulfates, derived from calorimetric measurements, are given in Tables 1-5. All entries in the tables were checked by examination of the original sources. Where available, data are given for the gas phase and either the liquid (lq) or solid (c) phase. Preference was given to gas and liquid phase data. 

The needed thermochemistry for many thousands of molecules is available from standard sources such as the JANAF tables. " Polynomial fits of this data in the form required by our kinetics software are also available. However, experimental thermochemical data is often lacking for many of the intermediate species that should be included in a detailed kinetics mechanism. Standard methods have been developed for estimating these properties, discussed in detail by Benson. ... 

The data in this appendix have been compiled from a number of sources. Nearly all of the critical property data are taken from Appendix A of The Properties of Gases and Liquids, Second Edition, by R. C. Reid and T. K. Sherwood, copyright 1966, McGraw-Hill Book Company. They are used with the permission of McGraw-Hill Book Company. Most of the thermochemical data (AG°, AH°f, and S°) were obtained from the following sources. 

Unless otherwise said, our preferred sources for enthalpies of formation of hydrocarbons are Reference 8 by Roth and his coworkers, and J. B. Pedley, R. D. Naylor and S. P. Kirby, Thermochemical Data of Organic Compounds (2nd ed.), Chapman Hall, New York, 1986. In this chapter these two sources will be referred to as Roth and Pedley , respectively, with due apologies to their coworkers. We will likewise also occasionally take enthalpies of fusion from either E. S. Domalski, W. H. Evans and E. D. Hearing, Heat Capacities and Entropies of Organic Compounds in the Condensed Phase , J. Phys. Chem Ref. Data, 13, 1984, Supplement 1, or E. S. Domalski and E. D. Hearing, J. Phys. Chem Ref. Data, 19, 881 (1990), and refer to either work as Domalski . 

CO)4FeSOOH- + C02. Squires128 had previously measured the bond strength of S02-OH- to be 61.9 kcal/mol, and calculated the bond strength of Fe(CO)5-OH- to be 60.3 kcal/mol. Combined with the heats of formation of Fe(C05) and OH-, they calculated A//f of Fe(CO)4COOH- = -267 kcal/mol. The thermochemical data of the relevant species involved in the catalysis, tabulated from numerous sources, are shown in Table 17. 

Kinetic studies in solution and in the gas phase have been playing an increasingly important role as a source of thermochemical data (see examples in chapter 15). Here we discuss how to relate thermochemical and kinetic information by approaching the subject as we did in the previous chapter by highlighting important practical issues and reducing to a minimum the description of theoretical models. In other words, the present chapter also relies on the material usually covered at the undergraduate level [1]. Further details can be found in more specialized books [55-59],... 

The experimental methods designed to investigate the energetics of gas-phase ions have been another important source of thermochemical data, particularly throughout the past two or three decades [9,10]. In this chapter, we discuss the main quantities that are measured experimentally and lead to reaction enthalpy values. 

Burcat [ Thermochemical Data for Combustion Calculations, in Combustion Chemistry. (W. C. Gardiner, Jr., ed.), Chapter 8. John Wiley Sons, New York, 1984] discusses in detail the various sources of thermochemical data and their adaptation for computer usage. Examples of thermochemical data tit to polynomials for use in computer calculations are reported by McBride, B. J Gordon, S., and Reno, M. A., Coefficients for Calculating Thermodynamic and Transport Properties of Individual Species, NASA, NASA Langley, VA, NASA Technical Memorandum 4513, 1993, and by Kee, R. J., Rupley, F. M and Miller, J. A., The Chemkin Thermodynamic Data Base, Sandia National Laboratories, Livermore, CA, Sandia Technical Report SAND87-8215B, 1987. 

Even for potential energy the other approach [93] required one parameter additional to oiu-s, apart from Dq, the latter quantity, equilibrium binding energy, is stated to be based on thermochemical data, but the cited source [95] indicates a value of dissociation energy 29q <2.84eV to arise from spectral analysis. Such an upper limit must be understood to provide an asymptotic limit for V(i ) at large i in a formula of Morse type because an attempted evaluation of 29e from only infrared spectral data is unreliable. The stated reason for the choice... 

Data for other substances can be obtained from the following critical compilations and online in the NIST Chemistry WebBook at http //www.webbook.nist.gov/ chemistry/ or from the NIST-TRC Databases available on disk. (Information can be found at http //www.nist.gov/srd/thermo.htm, or at http //srdata.nist.gov/ gateway/gateway keyword = thermodynamics.) An exhaustive list of earlier sources of tabulated thermochemical data can be found in Volume 1 of Chemical Thermodynamics, A Specialist Periodical Report [2]. A useful list of websites containing thermodynamic data is available at http //tigger.uic.edu/ mansoori/ Thermodynamic.Data. and.Property.html. 

Where do the thermochemical data that are used to determine the energetics of a reaction come from For closed-shell species that can be generated chemically via proton transfer, gas phase acidities (reaction [2]) and basicities (reaction [3]) are the principal sources. If the acidity or basicity for a reaction leading to a given ion is known, then the heat of formation for that ion can be calculated via Equations (4) and (5). This latter point is important, because this is the source for much of the ionic thermochemical data that are used for application of the no endothermic reactions tool. 

For an up-to-date, on-line source of thermochemical data for ion-molecule reactions, see S.G. Lias and J. Bartmess, Gas Phase Ion Chemistry webbook. ni st. gov/ chemi stry/ion . 

G3 is a recipe involving a variety of different models with the purpose of providing accurate thermochemical data. Original reference (a) L. A. Curtiss, K. Raghavachari, PC. Redfem, V. Rassolov and J.A. Pople, J. Chem. Phys., 109, 7764 (1998). For an up-to-date, on-line source of G3 data see (b) L A. Curtiss, Computational Thermochemistry, chemistry.anl.gov/compmat/ comptherm.htm ... 

The thermochemical data for 1,4-dioxane and 12-crown-4 come from our archival source that for 18-crown 6 come from summing those from V. P. Vasil ev, V. A. Borodin and S. B. Kopnyshev, Russ. J. Phys. Chem. (Engl. TransL), 66, 585 (1992) (enthalpy of formation, solid) and G. Nichols, J. Orf, S. M. Reiter, J. Chickos and G. W. Gokel, Thermochim. Acta, 346, 15 (2000) (enthalpy of sublimation). 

We will now consider a practical example of calculating thermochemical properties for the species CH3. Actually a lot is known about the CH3 radical, and we choose it as example in order to compare the calculated results with experimental data. The NIST-JANAF Thermochemical Tables [62] are a standard source for experimental thermochemical data, as well as moments of inertia, vibrational frequencies, and the like. The NIST-JANAF Tables use the same basic approach outlined here to calculate the temperature dependence for their thermodynamic data, based on species vibrational frequencies and moments of inertia. 

Insofar as electron impact mass spectrometry is concerned, the cycloproparenes almost always display a molecular ion. The primary source of fragmentation is by loss of a C(1) substituent radical to provide a cycloproparenyl cation. However, labelling studies have shown that loss of H from 1 and 11 (at least) occurs only after complete scrambling of the carbon atoms216217. The use of appearance energy measurements218 for the loss of Br from ionized 2-bromocyclopropabenzene (57a), when coupled with thermochemical data, have led to the prediction that cation 110 is more stable than the phenyl cation by at least 27.6 kcal mol"1 AHf of 110 is estimated at 311 kcalmol"1. 

The sources and magnitudes of thermochemical data have been the subject of many entries in this Encycl. The use of the data presupposes a general acquantance with chemical thermodynamics (next article) and with detonation theory (Vol 4, D268-L to D298-R). The principle difference between classic thermodynamics and the thermochemistry of reactive systems is that expins and deflagrations do not represent equilibrium processes. In principle, the heat of reaction is obtained by ... 

J. B. Pedley, R. D. Naylor and S. P. Kirby, Thermochemical Data of Organic Compounds (2nd ed.), Chapman Hall, New York, 1986. This is the chosen archival source of enthalpy-of-formation data, and so an unreferenced datum may be assumed to arise from this source. Where cited explicitly in the text, this volume will usually be referred to as Pedley . 

This program stores data for approximately 7800 compounds. Data come from a variety of sources. Those chiefly used for calculations in this work include Barin, I., Thermochemical Data of Pure Substances, VCH Velagsgesellschaft, Wein-heim, 1989 and 1993. 

Gas-phase methods also constitute a source of important information on basic physical properties of silylenium ions. In particular, the thermochemical behavior is well characterized (30,33,34,47,61). Thermochemical data are applied for the evaluation of relative thermodynamic reactivities of silylenium ions in some systems. For example, affinities of R3Si+ and R3C+ toward various bases may be compared as the heterolytic dissociation energies of corresponding bonds [Eq. (12)] (47,61). It was shown that... 

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