Search Rate Constants

Rate Constants for Reactions of Aliphatic Carbon-Centered Radicals in Aqueous Solution

Pedatsur Neta and Jan Grodkowski,*
Chemical Kinetics and Thermodynamics Division,
National Institute of Standards and Technology,
Gaithersburg, MD 20899

and

Alberta B. Ross
Radiation Chemistry Data Center, Radiation Laboratory, University of Notre Dame,
Notre Dame, IN 46556

J. Phys. Chem. Ref. Data 25: 709-1050 (1996)

*On leave from Institute of Nuclear Chemistry and Technology, Warsaw, Poland

Absolute rate constants for reactions of aliphatic carbon-centered radicals in aqueous solutions have been compiled and evaluated from the literature. Rate constants are included for reactions of radicals with inorganic and organic compounds and for decay by radical-radical reactions. The radicals were generated by radiolysis, photolysis, or other techniques, and their rate constants were determined generally by kinetic spectrophotometry. The tables include data for over 2,500 reactions of 373 radicals from 740 literature references.

Arrangement of Data:

These data have not been arranged for browsing, but may be searched by the name of either of the reactants. When more than one radical may be involved the radicals may be identified only by their origin and given a name such as "Radicals from glucose". The reactions are given by the use of line formulae whenever possible, or else abbreviations and symbols. Products are listed only for those reactions for which evidence has been obtained on the nature of the products; in some cases only the reaction type is given, e.g. addition, electron transfer, etc.

Values of k are in units of L mol^–1 s^–1, the unit of s^–1 is given with the value of k when it refers to a first-order reaction or a bimolecular reaction with water. Rate constants have been rounded to two significant figures and the author's error limits have been omitted. Most of the rate constants in these tables have uncertainties of ± 10% to ± 20%. In cases where the quoted error is large the value has been rounded to one significant figure. Upper and lower limits are indicated when reported. Rate constants for second-order decay of the radicals are given as k (not 2k) where –dR/dt = 2k[R]² has been determined. The molar absorptivity, e, used to calculate k in optical studies is given in the Comments. Rate constants for certain reactions have been determined with reference to the rate constant of another reaction; in those cases the reference values and the reference reactions are listed in the Comments.

The pH and ionic strength are quoted whenever they have been reported; in some cases the pK_a of the substrate is given in the Comments as an indication of the possible ionic forms of the substrate. The pK_a's have not been evaluated by the present authors. In some entries, pK_a's for the radicals have been quoted when reactions of the radicals in different ionic forms are presented. Temperature is assumed to be ambient when not otherwise specified.

The method for generation of the transient is indicated as is the method of measurement. The Comments include other data such as activation energy, activation enthalpy, activation entropy, activation volume, etc. When the symbol R is used in a Comment, such as in G(R) or k(R + R), it refers to the radical of the same entry.

Abbreviations and Symbols.

Introduction to Carbon-Centered Radicals.