Chemical Reactions of Energetic Atoms 1947-67

Carbon atoms in inorganic systems

The chemistry of energetic carbon atoms has been under intensive investigation at BNL with the object not only to ascertain the gross features of the chemical behavior but to determine details of the mechanisms of individual reactions. The specific methods used in this work, first developed here, involved the application of degradative procedures to molecular recoil products in order to identify loci of attack of the incident atoms on the substrate molecules. With the isotope carbon-11, it has been practicable to study systems with free choice of phase and temperature; and because C¹¹ is produced with relatively controllable accompanying radiation dosages to the system, explicit assessment of the role played by radiation chemistry in hot-atom reactions could be made.

It has been possible in some of these experiments to obtain information about the spin states of the reacting atoms and about the energy content of reaction complexes formed in the atom-molecule collisions. Insertion of species such as methyne (CH) and methylene (CH₂) has been shown to occur, and the recognition of the insertion reaction of the methylene radical was a major step in the advance toward understanding hot atom reactions. It has been shown further that the insertion reaction is followed essentially by an intramolecular step. Thus, well defined reaction sequences, rather than the previously accepted random disruption and recombination, are now ascribed to these systems.

A. P. Wolf, "Labeling of Organic Compounds by Recoil Methods," Ann. Rev. Nucl. Sci. 10, 259 (1960).
A. P. Wolf, "The Reactions of Energetic Tritium Atoms and Energetic Carbon Atoms with Organic Compounds," Adv. in Phys. Organic Chem. 2, 201 (1964).
H. J. Ache and A. P. Wolf, "Bond Energy Effects and Acetylene Production in the Reactions of Energetic Carbon Atoms with Alkyl Halides and Propane," J. Am. Chem. Soc. 88, 888 (1966).
A. P. Wolf, "Labeling of Organic Compounds by Irradiation and other Non-Synthetic Methods," Proc. Symposium Methods Preparing and Storing Labelled Molecules, Euratom 1966.

Inorganic systems

In addition to the study of chemical effects produced by recoil atoms in organic systems, effects produced in inorganic systems have also been the subject of investigation for a number of years at BNL.

It was early realized in work done here that a great complexity of recoil atom containing products often results from the reactions in a given inorganic crystal species. For example, P³² recoil in KH₂PO₄ produces twelve different identified P³² containing molecules - tripolyphosphate, pyrophosphate, hypophosphate, etc. Though a diversity of reactions occurs, the behavior is not governed by random recombination events, a fact borne out by the preferred-locus labelling found in some molecules with two or more phosphorous atoms.

In some cases the thermal reconversion ("annealing") of the recoil atom to the original chemical form takes place at low temperatures, in one instance -78ºC. Solution methods useful at such temperatures were developed for these investigations. Annealing is found often to consist of a set of individual processes, each having a discrete activation energy and each affected differently by radiation damage.

L. Lindner and G. Harbottle, "Chemical Behaviour of Phosphorus-32 Recoils in Crystalline Disodium Hydrogen Phosphate," J. Inorg. Nucl. Chem. 15, 386 (1960).
S. Veljkovic and G. Harbottle, "Low-Temperature Studies of Recoil Reactions," J. Inorg. Nucl. Chem. 24, 1517 (1962).

Applications

Information obtained in this work has been employed at BNL and elsewhere in the recoil synthesis of specifically labeled compounds. Isonicotinic acid hydrazide (Isoniazid), a drug much used in the treatment of tuberculosis and labeled only with difficulty by conventional techniques, was labeled at BNL some years ago and was successfully used in biological studies. The methods are especially useful, because of their relative ease and speed, for labeling with the short-lived C¹¹, a source of more penetrating radiations than those of C¹⁴.

Another important practical application in the development here of a method for the production of Cr⁵¹ of high specific activity. This method is now used world-wide to produce the Cr⁵¹ required for measurements of red blood corpuscle circulation and turnover.

G. Harbottle and A. G. Maddock, "The Preparation of Chromium-51 of High Specific Activity," J. Chem. Phys. 21, 1686 (1953).
A. P. Wolf, "Recoil Labeling of Organic Molecules with Special Reference to Compounds of Biological and Biochemical Significance," Proc. Symposium on Preparation and Biomedical Application of Labeled Molecules, EUR 2200e, p. 423, 1964

Last Modified: January 31, 2008