Title: Selected free radicals and critical intermediates:
thermodynamic properties from theory and experiment
Chairman: Branko Ruscic
Bérces, J. E. Boggs,
A. Burcat, A.
Császár, J. Demaison,
R. Janoschek, J.M.L.
Martin, M. J. Rossi,
J. Stanton, P.
Westmoreland, and F.
The main objective of this project activity is the continued compilation
and critical evaluation of published thermodynamic properties, including
the computation of accurate thermochemical data for selected free
radicals, that are of importance in atmospheric and combustion chemistry.
A distinguishing feature of the critical data evaluation is the systematic
utilization of all available kinetic, spectroscopic and ion thermochemical
results as well as high-level computations.
Knowledge of accurate thermochemical properties of free radicals
is of great importance in many branches of chemistry, in particular
atmospheric and combustion modeling. Thermochemical kinetic estimations
provide sometimes the only possibility for obtaining rate coefficients
and branching ratios for reactions of short-lived intermediates such
as free radicals. Thermodynamic quantities for stable molecules are
relatively well established. These are typically obtained from calorimetric
determinations, while heat capacities and entropies are derived from
the results of spectroscopic measurements. For free radicals and other
short-lived intermediates, direct calorimetric measurements are (in
most cases) not possible, while spectroscopic investigations require
more skill and sophisticated instrumentation. Consequently, thermochemical
data for a number of free radicals have a higher uncertainty than
the corresponding values of closed shell species. However, computational
chemistry has made great progress in reliability and accuracy. A solid
basis of thermochemistry now comprises the optimized combination of
experimental and computational results.
Such type of work has been initiated in our IUPAC
project 2000-013-1-100 which comes to a preliminary conclusion
at the end of the year 2003. Within this project the critical evaluation
of thermodynamic properties of 36 free radicals has been carried out.
The success of this work so far suggests an extension
of data evaluation beyond the initial goal to cover an increased number
of key radicals that play important part in atmospheric chemistry
and combustion. This requires the development of datasheets for about
25 further radicals.
extension of project #2000-013-1-100
project was presented at a poster session at the IUPAC Congress/GA
pdf - 1.00MB<
July 2005 - A substantial part of the work has
been completed and 12 papers have appeared or are in press during
2004-05. Additional papers are being written as the work progresses.
While the scope of this project was originally targeted to perform
a systematic critical evaluation of the thermochemistry of important
radicals, the scientific problems that are being encountered and formulated
as the evaluation effort progresses, have become a unique spiritus
movens, motivating ground-breaking research and development of new
general methods. This is especially the case in the areas of electronic
structure calculations (W3 and HEAT), and of dealing efficiently with
complex interrelationships inherently present in thermochemistry (ATcT).
The following publications have appeared from this project:
- Thermochemical Properties of the Hydroxy-formyl Radical
HO CO, and the Formyloxy Radical, HC(O)O, and their Role in the Reaction
OH + CO .H + CO2: Computational G3MP2B3 and CCSD(T)-CBS Studies
W. M. F. Fabian and R. Janoschek. J. Mol. Struct. TheoChem
713, 227 (2005)
- Ab Initio Determination of the Heat of Formation of Ketenyl (HCCO)
and Ethynyl (CCH) Radicals.
P. G. Szalay, A. Tajti, and J. F. Stanton. Mol. Phys. 103,
- IUPAC Critical Evaluation of Thermochemical Properties
of Selected Radicals: Part I.
B. Ruscic, J. E. Boggs, A. Burcat, A. G. Császár, J.
Demaison, R. Janoschek, J. M. L. Martin, M. L. Morton, M. J. Rossi,
J. F. Stanton, P. G. Szalay, P. R. Westmoreland, F. Zabel, and T.
Bérces. J. Phys. Chem. Ref. Data 34, 573-656 (2005)
abtract on the JCPRD website
- Pulsed Field Ionization Photoelectron-photoion Coincidence
Study of the Process N2 + h . .N + + N + e - : Bond Dissociation Energies
of N2 and N2 +
X. Tang, Y. Hou, C. Y. Ng, and B. Ruscic. J. Chem. Phys. 123,
- Thermochemical Properties of Free Radicals from G3MP2B3
Calculations, Set-2: Free Radicals with Special Consideration of CH2=CH-C=CH2,
cyclo-C5H5, CH2OOH, HO-CO, and HC(O)O.
R. Janoschek and M. J. Rossi. Int. J. Chem. Kinet. 36, 661
- W3 Theory: Robust Computational Thermochemistry in
the kJ/mol Accuracy Range.
A. D. Boese, M. Oren, O. Atasoylu, and J. M. L. Martin. J. Chem.
Phys. 120, 4129 (2004)
- Benchmark Thermochemistry of the Hydroperoxyl Radical.
B. A. Flowers, P. G. Szalay, J. F. Stanton, M. Kállay, J. Gauss,
and A. G. Császár. J. Phys. Chem. A 108, 3195
- Vibrational Spectrum and Thermochemistry of the Formyl
(HCO) Radical: A Variational Study by the Coupled Cluster CCSD(T)
Method with Complete Basis Set Extrapolation.
A. V. Marenich and J. E. Boggs. J. Phys. Chem. A 108, 5431
- Thermodynamic Properties of C1 and C2 Bromo Compounds
and Radicals: A Relativistic ab Initio Study.
M. Oren, M. A. Iron, A. Burcat, and J. M. L. Martin. J. Phys. Chem.
A 108, 7752 (2004)
- Introduction to Active Thermochemical Tables: Several
Key Enthalpies of Formation Revisited.
B. Ruscic, R. E. Pinzon, M. L. Morton, G. Von Laszevski, S. J. Bittner,
S. G. Nijsure, K. A. Amin, M. Minkoff, and A. F. Wagner. J. Phys.
Chem. A 108, 9979 (2004)
- B. Ruscic
Active Thermochemical Tables in: 2005 Yearbook of Science and Technology,
McGraw-Hill, New York, 2004, pp. 3-7
- Equilibrium Geometry of the Ethynyl (CCH) Radical.
P. G. Szalay, L. S. Thøgersen, J. Olsen, M. Kállay,
and J. Gauss. J. Phys. Chem. A 108, 3030 (2004)
- HEAT: High Accuracy Extrapolated Ab Initio Thermochemistry.
A. Tajti, P. G. Szalay, A. G. Császár, M. Kállay,
J. Gauss, E. F. Valeev, B. A. Flowers, J. Vázquez, and J. F.
Stanton. J. Chem. Phys. 121, 11599 (2004)
- Enthalpy of Formation of 2 . 3/2 SH.
A. G. Császár, M. L. Leininger, and A. Burcat. J.
Phys. Chem. A 107, 2061 (2003)
- Equilibrium Structure and Force Field of NH2.
J. Demaison, L. Margulès, and J. E. Boggs. Phys. Chem. Chem.
Phys. 5, 3359 (2003)
- Structural and Thermochemical Properties of the Hydroxymethyl
(CH2OH) Radical: A High Precision Ab Initio Study.
A. V. Marenich and J. E. Boggs. J. Chem. Phys. 119, 10105 (2003)
- Coupled Cluster CCSD(T) Calculations of Equilibrium
Geometries, Anharminic Force Fields, and Thermodynamic Properties
of the Formyl (HCO) and Isoformyl (COH) Radical Species.
A. V. Marenich and J. E. Boggs. J. Phys. Chem. A 107, 2343
- A Variational Study of Nuclear Dynamics and Structural
Flexibility of the CH2OH Radical.
A. V. Marenich and J. E. Boggs. J. Chem. Phys. 119, 3098 (2003)
- Thermochemical Properties of Free Radicals from G3MP2B3
R. Janoschek and M. J. Rossi. Int. J. Chem. Kinet. 34, 550
- The Enthalpy of Formation of 2 . CH.
A. G. Császár, P. G. Szalay, and M. L. Leininger. Mol.
Phys. 100, 3879 (2002)
- Anharmonic Force Field, Structure, and Thermochemistry
of CF2 and CCl2.
J. Demaison, L. Margulès, J. M. L. Martin, and J. E. Boggs.
Phys. Chem. Chem. Phys. 4, 3282 (2002)
Last update: 24 August 2007