Fusion of Inorganic and Organic Chemistry in the General Course' WILLIAM HERED Gary College, Gary, Indiana
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N RECENT years the emphasis in general chemis-
of covalent bonds leads to a simplification rarely possible in the use of inorganic molecules as examples. These covalent bond structures may be translated into their electron-pair equivalents after the electron theory has been presented. A discussion of the gradual development of polarity with the introduction of electron-attracting or electron-repelling atoms culminates in the development of the theory of ionization. Usnally the ionic bond is introduced first, but the simpler covalent bond is a more logical starting point. The free use of molecular models in connection with the structural formulas is suggested. The cry of "too much symbolism" is sure to be raised a t this, but there is very little in what we teach that is not symbolic to some extent. Even the notions of mass and length are symbolic; they describe the results of experiment just as do "picture" formulas and models. There should be no objection to picturization if the limitations of such pictures are carefully indicated. The concept of chemistry in space is amplified by a discussion of rate and mechanism of reaction. The dependence of rate on activation and on proper orientation lends itself admirably to treatment as a space phenomenon. For example, the "umbrella" mechanism for the substitution reaction RBr + OH- e ROH + Brr is simple enough for presentation and the accompanying idea of an intermediate reaction state is of considerable importance. A brief study of reaction mechanisms serves to moderate a too-excessive worship of the chemical equation. The fact that the equation is merely a record of the reactants and products of a reaction and gives no information as to the rate, mechanism, or formation of by-products is not to be ignored. The nature of catalytic action in solution is poorly explained in many general courses. This is due, in part, to the scarcity of illustrative material available in inorganic chemistry. Organic chemistry, on the other hand, furnishes an abundant source of such material. The esterification reaction is a beautiful example of homogeneous catalysis and the role of hydrogen and hydroxide ions is not difficult to present by means of structural formulas. Furthermore, by noting that the reverse reaction of the hydrolysis of esters is catalyzed by the same ions, is led smoothly into the concept of systems in on such and the absence of catalytic effects systems. ~h~~ the usual material on gas-phase equilihrium is supplemented by a fine example of equilibrium in solution and the latter topic is given the importance i t 1 Presented before the Division of Chemical Education at the deserves. lOlst meeting of the A. C. S., St. Louis, Missouri, April 9, 1941. 439
try has been transferred from the study of a mass of frequently irrelevant factual information to a consideration of the underlying principles of the science. This procedure has been justified on the ground that i t is of more permanent value not only to the embryo chemist but also to the non-chemistry major. During this time the presentation of the organic section of the general course has remained, on the other hand, largely a collection of isolated facts. A fundamental inconsistency exists in admitting the value of a deeper knowledge of chemistry and a t the same time adhering to an out-moded manner of presenting the organic content. Many of the principles of chemistry can better he developed through the use of illustrations taken from organic chemistry. Furthermore, the inclusion of concepts derived from organic chemistry serves to enrich the traditional material. These concepts may be so woven into the fabric of the general course that the usual sharp line of demarcation is obliterated. It is the purpose of this paper to propose a fusion of organic, inorganic, and physical chemistry in such a way as to make of the first-year course a representative survey of chemistry as a whole. This course will then serve not only those who plan further courses in the subject, but also those whose contact with the science begins and ends with the general course. The fact that chemistry is concerned with space and is not necessarily limited to two dimensions has not been emphasized sufficiently in the elementary course, and, accordingly, the average student finds the significance of structure and mechanism difficult to grasp in his advanced work. The space concept should be built up from the very beginning. Structure theory atfords a convenient means. Too frequently, since inorganic compounds are used in illustration, structure theory stops with the molecular formula. Certainly we would not he satisfied with a description of a house in terms of the number of bricks or the area of glass surface contained in i t ; the sense of incompleteness left in the mind of the student is unfortunate and unnecessary. afford a basis for The simpler organic further elaboration of structure theory. The phenomenon of isomerism is not too difficult to grasp; the "picture" formula is a logical extension of the molecular formula. Fortunately the constancy of valence of elements in organic compounds and the prevalence
The study of the periodic system atfords yet another opportunity to correlate the organic and the inorganic material. The tendency toward chain formation by elements such as lead, tin, silicon, and boron, which are neither strongly electronegative nor strongly electropositive, can be explained as a consequence of the type of bond exhibited in such chains. The culmination of this tendency in the compounds of carbon is a natural extension of this observation. The stability of long carbon chains is contrasted with the marked instability of even short chains of the elements mentioned above. The importance of carbon to life can then be treated as a result of the infinite possibility of variation in the structure of carbon compounds and the consequent possibility of a high specifiaty. The extreme complexity of proteins and high polymers extends this idea further and atfords an opportunity to introduce a few of the modern physical methods of investigating structure. The use of the ultra-centrifuge, the X-ray, and electron diffraction illustrates the cooperation of the sciences in the search for truth. The excursion into purely organic chemistry need not be long if the fusion has been effective. A brief mention may be made of typical homologous series as oxidation levels and of the meaning of the term oxidation-reduction as applied to the covalent bond. The work of the organic chemist in analyzing structures and in building molecules can be made an inspiring addition to this material. The proposed reorganization of the course will make necessary an examination of the traditional material in the light of its actual value to the student. The "sacred cows" of chemical antiquity must be slaughtered if there is to be room for more valuable matter. One such "sacred cow" is the balanced equation. Once the meaning of the law of conservation of mass has been transmitted, there is little further justifica-
tion for the exhaustive and thorough development of methods of balancing complex equations of little importance. Another "sacred cow" is the thorough development of the method of determining atomic weights. An understanding of the basis of the method is rarely acquired during the first year, and most students must resort to memorization of the operations involved. One solution is to defer an exhaustive discussion of this topic until later courses. In the same category are the topics of combining volumes, and of combination in simple and multiple proportions. Detailed descriptions of industrial processes should also be curtailed. It is debatable whether a knowledge of scrubbing towers and filter presses constitutes part of a liberal education. The degeneration of the general course a t the end of the year into a wealth of unimportant detail concerning the properties of metals is likewise out of keeping with the purpose of the course. The hasty touch of qualitative analysis designed to fix these details in the mind of the student and to bribe him into attention by giving him a problem to solve has as much justification as a section in hemstitching for the arousal of feminine interest. Finally there should be a judicious selection of the newer material. The principle of relevancy and not of recency should guide the selection. A course is not necessarily modem because the mesotron is mentioned. In the summing up, general chemistry must present a coherent and unified picture of the methods used by the chemist, his reasoning, and the products of his reasoning, in such a manner that the student whose contact with chemistry is limited to one year may retain something of value to himself and to his own philosophy of life.
