Sources of Thermochemical Data

There are a large number of scientific handbooks and textbooks that contain theamochemical data. In addition, many 

NIST (National Institutes of Standards and Technology) Scientific and Technical Databases (http //www.nist.gov/sid/thermo.htm), most notably the NIST Chemistry WebBook (2005), which contains an extensive collection of thermochemical data for over7000 organic and small inoiganic compounds. 

Lide and H. V. Kehiaian (Eds.), CRC Handbook of Thermophysical and Thermochemical Data, CRC Press, Boca Raton, FL, 1994. 

Binnewies and E. Milke (Eds.), Thermochemical Data of Elements and Compounds, 2nd rev. ed., Wiley-VCH, Weinheim, Germany, 2002. 

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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 ... 

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. 

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 . 

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... 

These latter assumptions make use of thermochemical data ancillary to the enthalpy of hydrogenation. These data are not just the enthalpies of formation of C02(g) and H20(lq), needed for his/her counterpart who measures enthalpies of combustion. The use of ancillary thermochemical information becomes imperative, e.g. the enthalpy of formation of an alkane that is the product of hydrogenating a diene of interest. It is an easy conceptual step to go from ancillary information to secondary sources of thermochemical data. This is consonant with our own bibliographic preferences and prejudices, in this paper we tacitly choose to cite secondary sources over primary sources. This strongly simplifies the writing and reading of our text at the risk of offending an occasional author of an uncited primary research paper. 

Ionization techniques are extremely important sources of thermochemical data for ions. Excellent chapters are given in Refs. 37, 41 and 42. 

We have recently initiated appearance potential (AP) studies in an attempt to determine D(Cp2Zr -OT3). AP measurements have many well knosvn limitations, but they are nevertheless a common source of thermochemical data (I), To obtain the desired Zr-C bond enthalpy, the AP values for eqs 5-7 must be considered. 

High-pressure mass spectrometry and pulsed high-pressure mass spectrometry have also been a source of thermochemical data for organometaiiic compounds (e.g., proton affinities, electron affinities, and bond dissociation enthalpies). The essential difference between both techniques is the fact that in the former the reactants are produced outside the collision cell. 

As illustrated in Fig. 1, there are essentially four methods for obtaining thermochemical data for the species in our reaction mechanism. The first choice is to find the needed data in databases or in the literature in general. This includes both published experimental data and published quantum chemical calculations, which can also be a reliable source of thermochemical data. If no information on a substance is available in the literature, one should consider whether it can be treated by group additivity methods. If a well-constructed group additivity method is available for the class of molecules of interest, the results, which can be obtained with minimal effort, will be comparable in accuracy to those from the best quantum chemistry calculations. If group additivity is not applicable to the molecules of interest, then we may want to carry out quantum chemistry calculations for them, as discussed in detail in an earlier chapter. In some cases, the effort required to carry out the quantum chemical calculations may not be warranted, and we may want to make coarser, empirical estimates of thermochemical properties. 

Chapter 7 presents a critical survey of sources of thermochemical data, their calculation or estimation, method of tabulation, instructions for carrying out calculations with respect to maximum technological utilization of the results of calculations and an example of the treatment of a system of practical interest errors, which may cause some uncertainty in the calculation, are briefly analyzed. 

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