Fred Basolo Northwestern University Evanston. IL 60201
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Systematic Inorganic Reaction Chemistry Inorganic reaction types, general methods of synthesis, and the periodic table
The teaching of inorganic reactions and syntheses, often called descriptive inorganic chemistry, has largely been ignored during the past couple of decades. The result is that we now have a generation of young chemists, including even PhD inorganic chemists, who know very little descriptive inorganic chemistrv. , This is certainlv not the fault of these very capable people, hut it isdefinitelGhe fault of we chemical t;duiators who have failed todo our id,. I aisume that our iob is to teach chemistry, which must include teaching both inorganic and organic reactions and syntheses. In these days of bringing suit against one's medicaidoctor, and even against one's own parents, it might occur to chemistry graduates to bring suit against their chemistry teachers for not having taught them even the most common chemical reactions. I wish to address my lecture to these common chemical reactions. These inorganic reactions were once taught in general chemistry courses,-hut some years ago the content for these courses turned away from reactions and syntheses. Many reasons are eiven for this. hut one reason almost always mentioned ib;hat studen~srefuse to memorize reactions and they think this iadull and boring. I eontend that it is possible to teach inorganic reactions and synthes~swithout the studenLs havine to memorize specific reactions, and without the lectures being dull and boring. ~
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One approach to teaching inorganic reactions without having students memorize specific individual reactions is to discuss these in terms of general reaction types, and to make extensive use of the periodic tahle of elements. Different approaches may he used to teach systematic reaction chemistry, but one which others and I' have found useful is that of classifying reactions under the following headings: I I1 111 IV V
Combination Decomposition Replacement
Metathesis Neutralization
We can easily make it clear to the students that thousands of specific reactions are known for each category, hut that one 'eed not memorize any of the specific individual reactions. One need only know, for example, that one subgroup of the combination reaction category is the reaction of a metal with a nonmetal. With some knowledge of the periodic tahle and trends in the oeriodic table. the student should be shown how to make ed&ated guesses of the reactions between different metals with different nonmetals. This allows the teacher a chance to stress the importance of the periodic tahle in terms of the maximum and minimum oxidation states of the ele~
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Volume 57, Number 11, November 1980 1 761
Fred Bssolo received his B.S. from Southern Illinois and the PhD from Illinois (Urhana) in 1943. He is Professorof Chemistry at Northwestern University, 4 where he has been on the faculty sincef 1946, serving as Chairman of the Chemistry Department 1969-72. He is a memher of the National Academic of Sciences and a Fellow of the AAAS, has received the ACS Awards for Research in Inorganic Chemistry and Distinguished Service in Inorganic Chemistry and was\ awarded the first Bailar Metal, in addition to numerous other awards, fellowships and lectureships. Author of several hooks and over 250 seie&ific papers, hehas served as Chairman of the Division of Inorganic Chemistry of the ACS and as Chairman of the Board of Trustees of the Gordon Research Canferences,and he is presently President of Inorganic Syntheses, Inc.
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ments, and the relative oxidizing power of the nonmetal. The teacher will have to be tolerant and grade the students' answers on the basis of their making good chemical sense, and not strictly on the basis of whether the particular reaction as written does or does not take place. This approach allows the student to learn chemistrv in a general aualitative fashion without having to memorize specific reacGon equations, and with the confidence that the answer given will be correct more than 90% of the time. Another example of teaching systematic inorganic reaction chemistry can be involved with the preparation (or manufacture) of elements from their compounds (or minerals). Surely we expect chemists to know how copper, commonly used in electrical wiring, is made from its low grade copper ore; and how chlorine, widely used in water purification, is produced from its mineral sodium chloride. The student starts
762 / Jwrnal of Chemical Education
bv recoenizine that elements can he made onlv from their &mpo&ds b;redox reactions. The element in the compound must either be reduced to its elemental zero oxidation state or i t must be oxidized. This can be done either chemically or electrolvticallv and the general categories for the meparation of e~emkntsfrom their compounds&e as follows: I. Oxidation of the Element 11. Reduction of the Element 111. Thermal Redox Reaction
The students will have to he told which are the common oxidizing and reducing agents. Also they will need to know that a few elements such as fluorine can be made electrolvticallv only, whereas other elements such as chlorine and aluminum are manufactured electrolvticallv because of the favorable economics of the process. ~ i t hee A a l redox reaction category is not often used to preoare elements, but we know it to be the method used by ~ i i e d tto l ~make oxygen, and the thermal decomposition of K3PbF7 does give Fp. A junior-senior level inorganic chemistry course should not have to teach these general inorganic reactions syntheses. I t should teach such topics as transition metal org&ometallic chemistry with its oxidative addition, reductive elimination, ligand migration, etc. reactions. It should teach the chemistry of the less familiar elements, boron chemistry, bioinorganic chemistry, solid state inorganic chemistry, etc. Yet can we justify teaching these currently fashionable topics a t the expense of teaching students how to make such common inorganic compounds as HzS04, NazCOa, KMn04, KpPtC14, etc.? I do not think so, and I hope that it will again be possible to teach this "bread and butter" type inorganic chemistry in our general chemistry courses.
' Bmolo, F.,and Parry, R W., J. CHEM. EDUC., 57, 172, (1980).
