Symposium on the Extent of Organic Analytical Methods
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ORGANIC CHEMISTRY AND THE ANALYTICAL PROGRAM AT M.I.T. ERNEST H. HUNTRESS, DAVID N. HUME, and LOCKHART B. ROGERS Massachusetts Institute of Technology, Cambridge, Massachusetts
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program of organic analytical instruction a t the Massachusetts Institute of Technology is based upon the needs of three distinct groups of students: (1) undergraduates, (2) graduate students specializing in organic chemistry, and (3) graduate students specializing in analytical chemistry. The needs of these groups are in some respects similar and in others very different. The program must be sufficiently flexible to meet the requirements of all, yet must fit a philosophy of teaching appropriate to each level. The teaching of undergraduate chemistry majors should avoid premature specialization. What is desired is a man well-rounded in his knowledge of chemistry and having a grasp of chemistry as an integrated whole. Attainment of this objective is not always promoted by the conventional groupings of chemical subjects in many undergradute curricula, which by division into traditional administrative units often tend to isolate rather than integrate the components of the subject matter. The separation of chemistry courses into subjects such as general chemistry inorganic qualitative analysis, inorganic quantitative analysis, organic chemistry, organic qualitative analysis, etc., however desirable from other standpoints, become a disservice to the student. The danger lies not so much in the organization of topics as in the segregation of concepts that may result. Ordinarily, the first two years of an undergraduate's chemical training emphasize the general aspects of the periodic table by covering the descriptive aspects and the separation methods of many of the common elements with only a comparatively small proportion of time devoted to carbon and its compounds. On the ot,her hand, the first course in organic chemistry owes its breadth to differencesin the properties of molecules rather than of atoms. Not only are the separation and identification procedures of qualitative organic analysis new to the student, but they appear to have little relation or application to the body of information acquired in prior subjects. Such complete administrative separation often deludes students into a corresponding compartmentalization of their chemical concepts.
The problem of presenting in a one-year beginner's course an integrated and balanced portrayal of chemistry is admittedly perplexing. Many teachers, appalled by modern demands with respect to the other elements, feel that to devote much time to the compounds of carbon is nearly impossible. Nevertheless, contemporary chemical industry has greatly changed and now involves in everyday practice so many organic chemical aspects that readjustment in a corresponding direction is not only desirable but even imperative. Further elaboration of this topic lies beyond the scope of the present symposium but the traditionally limited treab ment of organic chemistry in first-year courses has been contributory to an inadequate appreciation by the student of the necessity for an integrated rather than differentiated philosophy of study. That analytical chemistry provides an excellent framework for teaching either inorganic chemistry or organic chemistry is generally agreed by those who have seriously tried this procedure. The first course in qualitative analysis, although designed to organize the descriptive inorganic chemistry, contains many opportunities to integrate these with organic aspects. Organic precipitants (not including solvents like alcohol which are used for fractional precipitation of the alkaline earths) and lake-forming dyes are employed in nearly every qualitative analytical scheme. At the appropriate time, one lecture can be spent profitably in discussing the idea of "specific groups" and their selective actions with cations. Books such as that of Feigl' provide an interesting and comparatively simple discussion of studies of dimethylglyoximeand related compounds with regard to their specificity for the precipitation of nickel. Moreover, after contrasting the fact that cobalt forms a soluble intensely colored complex with dimethylglyoxime, further discussion of colorforming reagents becomes appropriate. Properly handled, these topics can be understood by students who have not yet taken any formal organic chemistry. FEIGL,F.,"Specific and Special Reactions for Use in Qualitative Analysis," Elsevier Publishing Company, Inc., New York City, 1940.
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in the Graduate and' Undergraduate Curricula In discussing separation methods in qualitative analysis, illustrations from organic chemistry can he used to advantage. Consideration of the extractive separation of ferric chloride or of iodine may he extended to include examples of the extraction of metalborganic compounds, a subject which is finding increasing importance in analytical chemistry, together with extraction of strictly organic substances such as that of organic acids by ether. Similarly, a discussion of the loss of elements by volatilization during the dissolution of the sample or the mention of fractional distillation as a method for separating compounds of elements such as arsenic and antimony can include examples illustrating the importance and general applicability of volatilization in organic chemistry. Finally, in pointing out the striking utility of ion exchange in such problems as the separation of the rare earths, one may draw from the organic field illustrations which employ the closely related technique of chromatography. By such devices as these the student begins to recognize the essential unity of chemistry and transitional frames of reference connect one aspect with the other. In teaching quantitative analysis, the opportunities for emphasizing the general relationships of the principles and techniques are analogous to those in the qualitative field. There is occasion, for example, to show that the behavior of acid-base and oxidationreduction indicators, even though these are complicated organic molecules, is understandable in terms of the already-familiar concepts of electrolytic dissociation and oxidation potential. The use of oxalates and simple organic acids as unknowns allows the instructor to point out that the same general methods and techniques used in inorganic analysis can he applied to many organic systems. However, general consideration of methods of determination of organic compounds is clearly premature and should be resewed for later courses. Just as the first course in qualitative analysis can be used to systematize the reactions of inorganic chemistry, systematic instruction in qualitative organic analysis provides an effective means of teaching organic reactions. The Massachusetts Institute of Technology pioneered in this subject and its values have been fully expressed el~ewhere.~Experience with this approach supplies reality to concepts and compounds which are otherwise too often vague abstractions. Its disciplines provide an indispensable supplement to the conventional study of unit laboratory processes involved in organic synthetic work. For these reasons every undergraduate chemistrv and chemical eneineerin~:
major is trained in the identification and characterization of organic compounds during the junior year as a part of the regular organic laboratory work. Having pursued the sequence of courses just outlined, the Massachusetts Institute of Technology senior undergraduate has had the necessary fundamental instruction in elementary inorganic, analytical, organic, and physical chemistry and is, therefore, in an excellent position to integrate his knowledge into a coherent whole. Such an opportunity is afforded by our course in instrumental analysis (perhaps better described as instrumental methods of solving chemical problems). Its experiments are selected to illustrate applications to every branch of chemistry and the corresponding lectures and class discussions expand and extend appropriately the particular techniques studied by each student in the laboratory exercises. Such an approach is not difficult. A consideration of the papers published on ultraviolet and infrared spectrometry, for example, emphasizes the importance of their organic applications. Increasing numbers of applications of polarography, potentiometry, and radiochemical techniques to organic problems are available from the current literature. This course in instrumental analysis is considered to he a very significant element in the organic analytical program of instruction. Finally, each senior may elect to take for one semester a four-hour lahoratory course in methods of quantitative microanalysis. By executing under supervision analyses for carbon, hydrogen, nitrogen, sulfur, halogens, and certain functional groups, the student gains not only a certain amount of facility with micro equipment, particularly the balance, but also a perspective which materially improves his discrimination in the interpretation of data so obtained. The present discussion has so far stressed the function of organic and instrumental analysis in the undergraduate curriculum. Let us finally consider briefly the opportunities afforded the graduate student, who is now in a position to utilize his broad foundation as a basis for particular specialized aspects. The relatively new analytical graduate program at the Massachusetts Institute of Technology was designed with special reference to the requirements of modern industrial laboratories. It is recognized that a substantial fraction of samples subjected to analysis are organic mixtures and that a versatile analytical chemist must be equally well trained in organic and inorganic methods. With this in mind we have visualized a balanced program in which all phases of organic analysis-qualitative, quantitative, and instrumental-are integrated. This is implemented by a 'HUNTRESS, E. H., 'The value of organic qualitative analysis three-semester course, expected of every analytical as a method of inshotion in organic chemistry," J. CKEM. major, which presents an up-to-date theoretical treatment of separation processes and determinative methEDUC., 7,158&92 (1930).
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ods, a discussion of the newer analytical reagents, and a survey of special topics such as spot testing, microtechniques, and statistical analysis. For the further training of graduate students whose major is either analytical or organic chemistry a course in advanced organic chemistry from the analytical viewpoint forms part of the regular program. Presupposing adequate training in qualitative organic analysis, this graduate subject is devoted to a systematic survey of the behavior of the principal organic functional groups withspecial reference to their detection and determination. Making use of the increased maturity and experience of its students, this course comprises review, expansion, and extension of prior training, frequently by special emphasis upon the behavior in qualitative and quantitative aspects of organic compounds with multiple functions of the same or different kinds.
JOURNAL OF CHEMICAL EDUCATION
Students (either graduate or undergraduate) electing to undertake their theses in the field of analytical research are especially encouraged to consider studies in the detection and determination of organic functional groups with emphasis upon the application of modern instrumental methods. Regardless of particular thesis topic, however, a student must be interested in and well acquainted with current progress in both the inorganic and organic fields in order to he considered a well-balanced analytical chemist. The integration of material afforded by constant interweaving of the analytical viewpoint with instruction in physical, inorganic, and organic chemistry is a perpetual reminder to the student that analysis is the key to progress in all. It is to the teacher a continual inspiration in maintaining his recognition that the student is not merely a vessel to he filled hut a torch to be lighted.
