THERM: THERMODYNAMIC PROPERTY ESTIMATION FOR GAS PHASE RADICALS and MOLECULES

We have developed a computer code for an IBM PC/XT/AT or compatible which can be used to estimate, edit, or enter thermodynamic property data for gas phase radicals and molecules using Benson's group additivity method. The computer code is called THERM (THermo Estimation for Radicals and Molecules). All group contributions considered for a species are recorded and thermodynamic properties are generated in old NASA polynomial format for compatibility with the CHEMKIN reaction modeling code. In addition, listings are created in a format more convenient for thermodynamic, kinetic, and equilibrium calculations. Polynomial coefficients are valid from 300–5000 K using extrapolation methods based upon the harmonic oscillator model, an exponential function, or the Wilhoit polynomials. Properties for radical and biradical species are calculated by applying bond dissociation increments to a stable parent molecule to reflect loss of H atom. THERM contains a chemical reaction interpreter to calculate thermodynamic property changes for chemical reactions as functions of temperature. These include equilibrium constant, heat release (required heat, ΔHr), entropy change (ΔSr), Gibbs free energy change (ΔGr), and the ratio of forward to reverse Arrhenius A-factors (for elementary reactions). This interpreter can also process CHEMKIN input files. A recalculation procedure is incorporated for rapid updating of a database of chemical species to reflect changes in estimated bond dissociation energies, heats of formation, or other group values. All input and output files are in ASCII so that they can be easily edited, expanded, or updated.

[1]  D. Golden,et al.  Revised group additivity parameters for the enthalpies of formation of oxygen-containing organic compounds , 1973 .

[2]  D. Griller,et al.  Thermochemistry of .alpha.-aminoalkyl radicals , 1981 .

[3]  R. Reid,et al.  The Properties of Gases and Liquids , 1977 .

[4]  David M. Golden,et al.  Hydrocarbon Bond Dissociation Energies , 1982 .

[5]  D. Golden,et al.  Thermochemistry of some six-membered cyclic and polycyclic compounds related to coal , 1977 .

[6]  Stephen E. Stein,et al.  High-temperature stabilities of hydrocarbons , 1985 .

[7]  John M. Hoffmann,et al.  Chemical process hazard review , 1985 .

[8]  D. Golden,et al.  Additivity rules for the estimation of thermochemical properties , 1969 .

[9]  E. S. Domalski,et al.  Estimation of the Thermodynamic Properties of Hydrocarbons at 298.15 K , 1988 .

[10]  R. Timonen,et al.  Kinetics and thermochemistry of the t-C4H9 radical. Study of the equilibrium t-C4H9+HBr⇄i-C4H10+Br , 1988 .

[11]  Heats of formation of alkyl radicals from appearance energies , 1988 .

[12]  S. Benson,et al.  Additivity Rules for the Estimation of Molecular Properties. Thermodynamic Properties , 1958 .

[13]  A. Castelhano,et al.  Heats of formation of some simple alkyl radicals , 1982 .

[14]  D. Golden,et al.  Predictive scheme for thermochemical properties of polycyclic aromatic hydrocarbons , 1977 .

[15]  Kenneth S. Pitzer,et al.  Energy Levels and Thermodynamic Functions for Molecules with Internal Rotation I. Rigid Frame with Attached Tops , 1942 .

[16]  D. Gutman,et al.  Kinetics and thermochemistry of methyl, ethyl, and isopropyl. Study of the equilibrium R + HBr .dblharw. R-H + Br , 1988 .

[17]  J. D. Cox,et al.  Thermochemistry of organic and organometallic compounds , 1970 .

[18]  W. Tsang.  The stability of alkyl radicals , 1985 .