Radiation Chemistry at the Radiation Chemistry Data Center

Data on short-lived chemical species have been documented at the RCDC in critically evaluated compilations on kinetics and other properties of transients from water and from inorganic and organic solutes. A bibliographic database was developed and it has been maintained and used to provide information services. The database also supports compilation activity on excited-state processes, mainly from photochemistry and photophysics.

Data compilations currently derive from two main areas:

1. Radical kinetics in solution
2. Thermodynamic and spectroscopic properties of free radcials

Printed compilations are found in the Journal of Physical and Chemical Reference Data and the NSRDS-NBS report series.
Rate constants for radical processes, including more recently added data, can be found by searching online via the World Wide Web or through the NDRL/NIST Solution Kinetics Database on your personal computer.

Kinetics of Radical Processes

Rate constants for primary radicals from the radiolysis of water, including hydrated electrons, hydrogen atoms, and hydroxyl radicals, were critically reviewed in a 1988 compilation. A compilation of kinetic data for nonmetallic inorganic radicals in solution was published in 1988. A recently completed compilation covers rate constants for metal transients in aqueous solution. Rate constants for aliphatic carbon-centered radicals in aqueous solution was published in 1996.

• Rate Constants for Reactions of Aliphatic Carbon-centered Radicals in Aqueous Solution
  P. Neta, J. Grodkowski and A.B. Ross
  J. Phys. Chem. Ref. Data 25 709-1066 (1996)
  The radiolysis of water produces short-lived primary radicals which react with aliphatic compounds such as alcohols, acids, amines, ethers, halogen compounds, amino acids, etc., to produce secondary radicals which undergo further reactions of addition, oxidation, reduction, abstraction, etc. Rate constants have been compiled for 2,500 reactions of 350 aliphatic carbon-centered radicals with various solutes. The radicals include:
  
  • alkyl
    
  • hydroxyalkyl
    
  • haloalkyl
    
  • alkoxyalkyl
    
  • carboxyalkyl
    
  • aminoalkyl
    
  • benzyl and ketyl radicals
    
  • other substituted alkyl radicals
    

• Critical Review of Rate Constants for Reactions of Transients from Metal Ions and Metal Complexes in Aqueous Solution
  G.V. Buxton, Q.G. Mulazzani and A.B. Ross
  J. Phys. Chem. Ref. Data 24 1055-1349 (1995)
  Kinetic data for transient metal species in aqueous solution have been critically reviewed. The compilation covers over 2000 measurements of rate constants involving 660 metal ions and metal complexes from Groups 4-15. Data have been collected from 500 publications through 1993. Lanthanides and actinides are not included.

• Rate Constants for the Decay and Reactions of the Lowest Electronically Excited Singlet State of Molecular Oxygen [Singlet Oxygen] in Solution. An Expanded and Revised Compilation
  F. Wilkinson, W.P. Helman and A.B. Ross
  J. Phys. Chem. Ref. Data 24 663-1021 (1995)
  Reactions of singlet oxygen are of much current interest because of their importance in photooxidations of chemical and biological systems, including reactions used in photo-chemotherapy. Rate constants for the chemical reaction and physical deactivation of singlet oxygen have been critically compiled from the literature through 1993. Solvent deactivation rates are tabulated for 145 solvents and second-order rate constants for 1,915 compounds with singlet oxygen are reported. This publication supersedes Wilkinson and Brummer, J. Phys. Chem. Ref. Data 10 809 (1981).

• Rate Constants for Reactions of Peroxyl Radicals in Fluid Solutions
  P. Neta, R.E. Huie and A.B. Ross
  J. Phys. Chem. Ref. Data 19 413-513 (1990)
  Peroxyl radials (ROO) are important reactive intermediates in organic and biological oxidations, and in atmospheric chemistry, which are formed by the addition of oxygen to alkyl radicals. Fast kinetic techniques initiated by radiolysis or photolysis have been used to obtain absolute rate constants for reactions of alkylperoxyl and substituted alkylperoxyl radicals. Rate constants in aqueous and nonaqueous fluid solution have been compiled from the literature through 1989.

• Rate Constants for Reactions of Inorganic Radicals in Aqueous Solutions,
  P. Neta, R.E. Huie and A.B. Ross
  J. Phys. Chem. Ref. Data 17 1027-1284 (1988)
  One-electron transfer oxidations and reductions by inorganic radicals are important in atmospheric and industrial processes. Rate constants have been compiled for reactions of various inorganic radicals produced by radiolysis or photolysis, as well as by other chemical means, in aqueous solutions. Radicals have been derived from carbonate, azide, nitrite, nitrate, phosphite, phosphate, sulfite, sulfate, selenite, thiocyanate, chloride, bromide, iodide and formate ion. Rate constants for reactions of ozone and various radicals from N, S, Se, Cl, Br and I compounds are also included.

• Representative Rate Constants for Radical Reactions of Biologically Important Molecules
  P. Neta and A.B. Ross
  Chemical Kinetics of Small Organic Radicals, Volume IV, Reactions in Special Systems, Z.B. Alfassi (ed.), CRC Press, Inc., Boca Raton, FL, 1988, p.187-212

• Critical Review of Rate Constants for Reactions of Hydrated Electrons, Hydrogen Atoms and Hydroxyl Radicals in Aqueous Solution
  G.V. Buxton, C.L. Greenstock, W.P. Helman and A.B. Ross
  J. Phys. Chem. Ref. Data 17 513-886 (1988)
  Kinetic data for the radicals H and OH, and the hydrated electron in aqueous solution have been critically reviewed. Rate constants of the radicals have been measured directly mainly by pulse radiolysis. When directly determined values have not been reported and steady-state determinations are available, selected and recommended values have been used to normalize relative rates. Data for over 3,500 reactions are tabulated.

• Rate Constants for Reactions of Radiation-Produced Transients in Aqueous Solution of
  S. Gordon, J.C. Sullivan, and A.B. Ross
  J. Phys. Chem. Ref. Data 15: 1357-1367 (1986)

• Reactivity of Hydroperoxyl/Superoxide Radicals in Aqueous Solution
  B.H.J. Bielski, D.E. Cabelli, R.L. Arudi, and A.B. Ross
  J. Phys. Chem. Ref. Data 14 1041-100 (1985).
  One-electron reduction of oxygen produces the superoxide radical which is associated with damage to biological systems. Kinetic data for the superoxide radical and its protonated form, hydroperoxyl radical (pKa = 4.8), in aqueous solution have been critically assessed. Rate constants for more than 300 reactions with organic and inorganic ions, molecules and other transient species have been tabulated.

Thermodynamic and Other Properties of Radiation Induced Transients

Some earlier data compilations at the RCDC covered: absorption spectral data for transient inorganic radicals, electron mobilities and free ion yields, the radiolysis of selected substances (methanol, ethanol, nitrous oxide and ammonia) with G values (radiation yield).

• Reduction Potentials of One-Electron Couples Involving Free Radicals in Aqueous Solution
  P. Wardman,
  J. Phys. Chem. Ref. Data 18 1637-1755 (1989)
  Reduction of an electron acceptor (oxidant), or oxidation of an electron donor (reductant), is often achieved stepwise via one-electron processes in which the intermediate is a free radical. The reduction potentials of such one-electron couples are of value in predicting the direction or feasibility, and in some instances the rate constants, of many free-radical reactions. Electrochemical methods have limited applicability in measuring these properties of frequently unstable species, but fast, kinetic spectrophotometry (especially pulse radiolysis) has widespread application in this area. Tables of about 1,200 values of reduction potentials of about 700 one-electron couples in aqueous solution are presented. The majority of organic oxidants listed are quinones, nitroaryl and bipyridinium compounds. Reductants include phenols, aromatic amines, indoles and pyrimidines, thiols and phenothiazines. Inorganic couples largely involve compounds of oxygen, sulfur, nitrogen and the halogens. Proteins, enzymes, and metals and their complexes are excluded.

• Optical Spectra of Nonmetallic Inorganic Transient Species in Aqueous Solution
  G.L. Hug
  NSRDS-NBS 69 (1981)

NDRL/NIST Solution Kinetics Database

The NDRL/NIST Solution Kinetics Database (Version 3.0) includes chemical kinetic data for free radical processes involving primary radicals from water, inorganic radicals and carbon-centered radicals in aqueous solution, organic peroxyl radicals in various solvents, metal transients in aqueous solution and rate constants for chemical reaction and physical quenching of singlet molecular oxygen in solution. Data from the literature through 1994 have been compiled and evaluated; recommended values of rate constants are designated for certain reactions.

Version 3.0 contains:

• 14,000 rate determinations
• 10,800 reactions
• 11,600 chemical species which are reactants or products.

You may search by reactants, products, chemical species containing a particular element, chemical name fragment, author or a particular reference. The search programs are based on the software for the NIST Chemical Kinetics Database which contains data for gas-phase reactions.

The database functions on any MS-DOS or PC-DOS computer and requires a hard disk with 10 MB free space.

Published by: A.B. Ross, W.G. Mallard, W.P. Helman, G.V. Buxton, R.E. Huie and P. Neta
Other contributors: B.H.J. Bielski, D.A. Cabelli, C.L. Greenstock, J. Grodkowski