Thermal Reactions of Systems in Solution 1947-67

Inorganic chemical reactions

The Department has done pioneering work on the mechanisms of electron transfer and of substitution reactions of inorganic compounds in solution.

Rates of various one-electron exchange reactions between metal ions have been successfully measured, and the long-standing problem of the ferrous-ferric exchange was solved. This has stimulated many investigations in this field of chemical kinetics. It has been found that electron transfer from iron(II) and vanadium(II) proceeds via binuclear complexes in which the donor and acceptor metal ions are connected via a bridging group. Bridging groups vary enormously in their ability to promote electron transfer.

Certain unsymmetrical groups possess two different sites for binding to a metal center. Two complexes containing chromium(III) and thiocyanate have been prepared. In one complex the thiocyanate is attached to the chromium through the nitrogen atom and in the other through the sulfur atom. These two complexes differ considerably in their properties, and they afford one of the very few examples of linkage isomerism. A novel type of intramolecular reorganization reaction, the mercury(II) catalyzed reorganization of a thiocyanate complex, was discovered. In this reaction the metal atom moves from one end of the thiocyanate group to the other. This process may have important implications for mechanisms of more complex reactions.

J. Silverman and R. W. Dodson, "The Exchange Reaction Between the Two Oxidation States of Iron in Acid Solution," J. Phys. Chem. 56, 846 (1952).
N. Sutin, J. K. Rowley, and R. W. Dodson, "Chloride Complexes of Iron(III) Ions and the Kinetics of the Chloride-Catalyzed Exchange Reaction Between Iron(II) and Iron(III) Ions in Light and Heavy Water," J. Phys. Chem. 65, 1248 (1961).
A. Haim and N. Sutin, "The Reactions of Isothiocyanatobis(ethylene- diamine)cobalt(III) Complexes with Chromium(II) and the Linkage Isomerization of the Monothiocyanate Complex of Chromium(III)," J. Am. Chem. Soc. 88, 434 (1966).
M. Orhanovic and N. Sutin, "The Mercury(II)-Catalyzed Isomerization of the Sulfur-Bonded Monothiocyanate Complex of Chromium(III)," J. Am. Chem. Soc. 90, 538 (1968).

Complex organic reactions at low temperatures

At very low temperatures the chemical behavior of systems is often simplified because reaction velocities are greatly decreased and because many perturbations are diminished or eliminated. It thus becomes possible to study with relative ease species which at ordinary temperatures have only transitory existence. The study of chemical reactions in solutions at very low temperatures has had much development at BNL. One of the substances studied is chlorophyll b, which, in alkaline media at ordinary temperature, reacts to produce a short-lived, irreversibly disappearing, red intermediate. At l50 K measurements were made of this substance undergoing slow, reversible reactions. Similarly, phosphorescences were observed which would have been quenched at higher temperatures and which have proved to be useful in the analysis of substances of biochemical interest.

S. Freed and K. M. Sancier, "Reversible Reaction of Chlorophyll Giving the Red-Brown Intermediate of the Molisch Phase Test," Science 11, 655 (1953).
S. Freed and M. H. Vise, "On Phosphorimetry as Quantitative Microanalysis with Application to Some Substances of Biochemical Interest," Anal. Biochem. 5, 338 (1963).

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Last Modified: June 28, 2012