Introduction The genesis of the State of the Art Symposium on Radiation Chemistry, held a t the Second Chemical Congress of the North American Continent in Las Vegas, Nevada on August 25 and 26, 1980, goes back several years to the time when Glenn Crosby and I discussed the concept of the State of the Art Symposia: to bring to chemical educators a knowledge of research areas in chemistrv that thev" mieht .. otherwise not obtain in their own teaching and research experience. For a lone time. I and other researchers who use the techniques of radiation chemisrry h a w ~lt.spi~~red ahout its relative absence in thr ch6:miral educatim curriculum. Althougl~the field of radiation chemistry is quite vigorous, with many national and international meetings bringing together scientists whose interests cross the many disciplinary boundaries hetween chemistry and biology, medicine, and physics, the principles and practice of radiation chemistry do not appear in the undergraduate or, except for very few highly specialized courses, eraduate curricula. In the first instance, the distinction between radiation chemistrv and radio- or nuclear chemistrv must be clarified. has not t~ecrssnrilyheen Ilnfortunntely. such a d~stitwti~m madv until fairlv recentlv so rhat, historira.1~ . nw,lkine, . - rodiation and radio-chemistry have been interchangeable terms. Current usaee renards radiation chemistry as dealina with the chemical effe~t~induced by the interaction of ionizing radiation (e.~.. hiah-energy - alpha . ~articles, . .. electrons, electromagnetic gamma rays and x-rays, elc.) with matter. Because the interaction is very energetic, ionization and excitation occur which lead to a cascade of reactions. Nuclear chemistry deals with the chemical result of the decay of unstable nuclei or the capture of energetic particles: changes in the atomic number and weight of atoms. Most general chemistry textbooks have a chapter, or a t least a section, on nuclear decay, radioactivity, and nuclear reactions. Although we may never get to that chapter in our general chemistry courses because of the time spent on wave mechanics, molecular orbitals, and thermodynamics, we encourage the students to understand the concepts of radioactive half-life, binding energy, and nuclear stoichiometry. It is important for the student to be familiar with the chemistry of the transuranium elements, the use of isotopic tracers in mechanistic and analytical studies, and the processes of fission and fusion. Aspects of nuclear chemistry re-emerge in the curriculum in analytical chemistry and occasionally in an upper level course in radiochemistry that may have a laboratory component dedicated to the techniques of handling "hot" materials. In contrast, there is virtually no concern expressed in the entire chemical curriculum about the chemistrv that results when the high energy emissions from the decay bf radioactive nuclei imwinee on matter. Not onlv do our students remain unaware of t i e detailed chemical effects of radiation, hut it is likely that their teachers, never having had courses themselves in the subject, have the same lack of knowledge. The events of March 1979 a t Three Mile Island and the ongoing controversy about nuclear power, nuclear waste, and &erapeutic X-rays make it imperative that this ignorance he ended. This noint is heine recoinized bv the federal eovernment in the ekahlishmenrof taik forces" to review thz status of the nhvsics., chemistry. " , and hioloev -" of radiation effects. A casual examination of general, physical, and biochemistry texts reveals that discussion of the chemical effects of radiation is totally absent. There appears to be only one current comprehensive textbook in the field.' The most recent detailed article in the Journal of Chemical Education on the chemical
-
.
A
'Spinks, J. W. T., and Woods, R. J., "An Introduction to Radiation Chernistry,"Znd Ed., John Wiley & Sons, New York, 1976. ZAllen,A.O., J. CHEM. EDUC., 45,290 (1968).
effects of ionizing radiation appeared in May 1968.2 It must be recognized that the history of radiation chemistry is as old as the discoverv of radioactivitv. hv Becouerel and of X-rays by Roentgen. Perhaps radiation biology is a bit older than its chemical countemart because the initial effects of radiation were found to be physiological, often from selfexperimentation. Early workers, such as the Curies, Giesel, Ramsay, and Soddy, noted that the action of the radiation from radium salts upon water led to its decomuosition; by 1909, the stoichiometry of the reaction had heen-established Hz02 + H2. After by quantitative measurements: 2 H20 world War I, the development of intense X-ray sources changed the techniques required to perform radiation chemical studies; the efforts during and since World War I1 have made radioactive sources and high energy accelerators nracticallv standard lahoratorv items.
-
the st&eeof the art of radiatidn chemistry in order to povid; a basis of bringing the material, to some degree, to our students. The Symposium was organized to he tutorial in nature with a strong ped~gilgicalemphasis; the invitd lmrtiripants, dl of ulwm are experts i n rhr ileld, n e w a w 4 1,) Le, for their oral and written presentations, the best teachers they have ever been so that the basic material can he reenforced to provide some lasting effect. This Symposium issue is highly structured with the later papers built upon the foundations of the earlier ones. The first four papers are devoted to background material for those to come. The paper by Dorfman (p. 84) establishes the hasic principles and techniques of radiation chemistry; Willis (p. 88) and Lipsky (p. 93) examine radiation effects in gas phase and non-polar fluids, respectively. Because there is so much concern with the behavior of aqueous solutions, which includes biological systems, Schwarz's review (n. 101) of the eeneration of radicals in water is especially important. The next four papers deal with the application of radiation chemical techniques to fundamental research in physical and inorganic chemistry. Sevilla (D.106) examines the esr rowert ties of radiation-uroduced free radicals and Neta (p. l i 0 ) discusses the redoxpoperties of free radicals which govern their reactivity. The papers by Sellers (p. 114) andHoffman and Whitburn (p. 119) review the generation and behavior of metal ions in unusual valency states and ligand-radicals coordinated to metal centers. ~ f t & Simic's paper (0. . . . 125) on free radical mechanisms in autox~d;jtionprocesses, tlw next five papers examino radiation effe, t.; in hiolog~cal>ystem,: Hedpath (p. 1.31) MI simple hioThomas dlemical :\%ems. N'ard tn. 1'1.5 an Lenetlc t~~aterial. and Chen (p. 140) on organized assemblies, Biaglow (p. 144) on mammalian cells, and Greenstock (p. 156) on cancer therapy. The final two papers deal with the more practical aspects of radiation chemistrv. T a u b (0. 162) presents the chemistry involved in the preservation of food by radiation, and Silverman (D. 168) concludes with a review of the industrial applications of radiation processing. In this way, you can see how the basic principles and some of the research discoveries are applied to the solution of practical problems. I hove that these oawers will enable vou to achieve an understanding of radiation chemistry so that some of its concepts can he aoolied to vour educational tasks. Perhaps this un.. derstnndiny will alsu hr 11wfi11 in your pt,r.iond examination ot rhr role of radistim in 11119nuclear and ~wst-ThreeMile Island world. Morton 2. Hoffman Svrnoosiurn Oraanizer . . Boston ~ G v e r s i t y Boston, MA 02215
-
Volume 58 Number 2
February 1981
83
