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The following article is the text of a symposium presentation at the Tenth International Conference on Chemical Education, August 20-25, 1989, University of Waterloo.


 

Organic Chemistry – The Beginning of Organized Understanding of Chemistry

Chemistry is recognized as "a central science that provides fundamental understanding needed to deal with many of society’s needs" [1]. Why then do chemistry courses rank among those least attractive for students in an undergraduate curriculum? In the United States this decline in interest is clear and alarming. In 1978 nearly 12,000 students graduated from its colleges and universities with a major in chemistry. By 1988, only 10 years later, that same number was less than 9,000 [2]. Furthermore, among first-year students, interest in the physical sciences has declined by one-third over the period 1977-1987 [3]. If this trend continues, and demographics alone demand that it will, we will reach a time, which is already evident in U.S. high schools, when chemistry is no longer taught by chemists and chemical education, as we know it today, will rank, as does Latin as a language of discourse and understanding, among those programs that service other disciplines and professions. The present time presents us with great need to change the way in which chemistry is presented.

In this article I hope to convince you that the curriculum for chemistry is in drastic need of revision and that Organic Chemistry should be a cornerstone for introducing students to the wealth of excitement and discovery that exists in our discipline. I will also tell you that we have a great need for new and innovative approaches to chemistry education, especially in Organic Chemistry, that bring students to an awareness of the challenges and opportunities that exist in the "central science." Finally, I will comment on the specific components of Organic Chemistry, including its laboratory program, that are in need of revitalization.

General Chemistry and the Core Curriculum for Chemistry

The traditional core curriculum for chemistry programs begins with an introduction to chemistry that is normally devoted to chemical principles and their applications. The introductory course serves a broad clientele, from potential chemistry and biology majors to engineering, premedicine, nursing, and a variety of other pre-professional students. It is, in fact, a major "service course" in colleges and universities, one that has politically, at least in the United States, justified a significant portion of chemistry faculty size and budgetary support.

The design of the introductory chemistry course originally provided an overview of the discipline with content distributed to highlight the major fields of disciplinary development. Then, and I am now speaking of a time prior to 1960, it was not uncommon to find inorganic chemistry integrated with physical and analytical principles, although organic chemistry, except in examples used for combustion, hybridization, and weak acids, among others, was left until the end, and often omitted. Introductory chemistry was intended to bring to all students a common background and understanding, although anyone who has taught such a course quickly comes to the realization that students who complete the course in introductory chemistry do so with vastly different levels of understanding. Indeed, although expectations are often lower and quantitative principles are taught to two significant figures rather than four, the high school course in chemistry covers virtually the same material as does the first year college course.

The time has come to challenge the requirement that students initiate their college study of chemistry with an introductory in General Chemistry, except for those students who have not previously taken a high school chemistry course or whose preparation in the high school course is judged to be inadequate. For students who have come to college with adequate preparation, the General Chemistry course is often repetitious and boring. Its physical orientation, which minimized the descriptive aspects of chemistry that have attracted students into chemistry in the past, defines chemistry too narrowly.

We must recognize that students who enter college motivated and/or prepared to enter a career in which chemistry is a prerequisite are being pulled in many directions. When they see chemistry as a science of atomic structure, molecular orbital theory, molarities, solubility products, and gas constants, how can they begin to understand its role in the discovery and design of new materials for the transmission of information, the synthesis of complex biologically important structures, or the detection, characterization, and quantification of chemical species at sub-picogram levels in environmental analyses?

The American Chemical Society’s Committee on Professional Training, which has the responsibility to broadly define programs of study for students who aim to be professionals in the chemical sciences at approved schools, has provided guidelines for the Core Curriculum. In the 1988 Extension of Guidelines, they are [4]:

  • Undergraduates should have a minimum of 28 semester credit-hours of basic instruction with comparable emphasis on:
    • elementary and intermediate inorganic chemistry
    • elementary chemical analysis and instrumental methods of analysis
    • fundamentals of organic chemistry, including bioorganic chemistry
    • principles of physical chemistry, including thermodynamics and equilibria, chemical kinetics, introductory quantum and statistical mechanics, and spectroscopy
  • The 28 semester credit-hours of study should include the equivalent of 7 semester credit-hours (300-350 contact hours) of laboratory instruction in:
    • synthesis and characterization of inorganic and organic compounds
    • elementary chemical analysis and instrumental methods of analysis
    • experimental physical chemistry
  • Laboratory instruction should include practical experience with instrumentation for spectroscopy, separation techniques, electrochemical methods, and computerized data acquisition and analysis.

These are, of course, minimum standards, and they do not infer requirements for the total chemistry curriculum for undergraduate students who may be directed to emphases in chemistry, biochemistry, polymer science, or education. They do, however, make a profound statement and that is that a core of knowledge exists which every student who professes to be a chemical scientist should know.

Organic Chemistry as a Cornerstone of Chemical Education

There is a wealth of organized knowledge about chemistry in the Introductory Organic Chemistry course, and the beauty of its expression lies in the integration of principles and their applications, of structure, dynamics, and synthesis. No other subdiscipline of chemistry possesses the uniformity of content that characterizes the first course in Organic Chemistry. Principles of chemistry are explained through applications with compounds containing carbon and hydrogen rather than with examples that span the breadth of the periodic table.

Restriction in the content of Organic Chemistry to only a few elements provides a distinct advantage in describing chemical principles. In hybridization theory, for example, Organic Chemistry is most concerned with sp, sp2, and sp3 atomic orbitals, and what better examples can be found for their application than in acetylene, ethylene, and ethane? Rather than beginning with the entire spectrum of hybrid orbitals, as one does in General Chemistry, why not, as in Organic Chemistry, introduce the few and allow subsequent courses to build upon this foundation? Hess’s Law is an integral part of thermodynamics found in General Chemistry courses, but what better examples can be found than those from the heats of combustion of organic compounds. And what better treatment can be found for the integration of kinetics, rate laws, and mechanisms of reactions than in SN1 and SN2 nucleophilic substitution processes?

Organic Chemistry is the first course from which a 3-dimensional view of molecules is of fundamental importance for student understanding. Chirality as a concept and structural design is most often introduced for the first time in that course and integrated into chemical reactions and their mechanisms. From this essential 3-dimensional understanding of molecular structure, taken together with molecular geometry and conformational flexibility, comes the realization that chemistry is indeed central to understanding complex biological processes and the rigid designs that are the essential elements of molecular devices.

With engineering students expected in most cases, among students who are drawn to a career in which chemistry is a prerequisite, the vast majority are best served by an introductory course in Organic Chemistry. Students interested in molecular biology, in medicine, in nutrition, and in petroleum geology, among others, would find added stimulus from chemistry introduced by Organic Chemistry. Even for students who are not oriented to these careers, Organic Chemistry holds principles and understandings that are fundamental to chemistry but are often overlooked in a General Chemistry course.

Problems with Organic Chemistry

"The course is too detailed. The textbooks, now more than 1200 pages, are too long." So say many students who have passed through this demanding course. Organic Chemistry is filled with factual information – 20 ways to synthesize an alkene and 40 reactions of alkenes, for example – often to the exclusion of the very principles that have characterized its unique importance.

"There is nothing worthwhile left to discover in Organic Chemistry" is another comment that is expressed too often. How exciting is the discovery of a new way of making cyclohexene when there are ten alternative methods? Missing from most textbooks and even lectures are descriptions of the relative importance of specific methodologies. Too few examples of the applications of Organic Chemistry to societal uses and problems exist in textbooks.

There is a core knowledge that all students who undertake a course in Organic Chemistry should understand, and that core is not devoted solely to factual details. Comprehensive chemical knowledge is expanding exponentially, and those details that are relevant to a particular problem are often changing faster than one’s ability to absorb them. Consequently, our students are served better by an educational emphasis on concepts with examples that appropriately highlight this basic framework and attract their interest. With a firm grasp of these fundamentals, students can then draw from the organized body of chemical knowledge those facts that are relevant to the solution of a particular problem.

Standardized examinations, which are so popular in professional training, have prompted Organic Chemistry’s emphasis on factual information. The effectiveness of a course in Organic Chemistry is often judged by its ability to include those specific items of information that are included in multiple choice examinations, and less often on the relevance of the information to chemistry or to society. In the United States the standardized Medical College Admission Test (MCAT) has influenced too much of the content of the Organic Chemistry course, although the absence of a separate examination for chemistry in the near future will minimize its importance and, with its absence, the relevance of chemistry for a career in medicine.

The pressure of standardized examinations and the basic conservatism of instructors provide a resistance to change the content of a course in Organic Chemistry. Many of you can recall your own introduction to the "Wurtz reaction," even in the 1960’s, as one of the five basic methods for the synthesis of alkanes. How many textbooks still treat carbonyl condensation reactions basically the same was as they were described 40 years ago?

Textbooks for Organic Chemistry are today almost as numerous as those for General Chemistry. Virtually all of them are organized according to functional groups, although differences do exist in their relative placement. Because of the excessive production costs of a new textbook, new and potentially innovative approaches are discouraged, and this further jeopardizes change. Could a "Cram and Hammond" be published today? I think not.

The laboratory program for Organic Chemistry continues in most institutions as a test tube science without student access to the basic chromatographic and spectroscopic instrumentation that are so essential to the rapid advances that have characterized this science. As a consequence, students view Organic Chemistry as it existed more than thirty years ago, and their enthusiasm has diminished. The recent attention given to micro-scale laboratories has been a valuable development, especially in reducing laboratory costs and waster disposal problems, but this approach can only be effective if students have access to the instrumentation necessary for characterization and evaluation of purity.

Organic Chemistry in the Year 2000

Significant changes have taken place in the chemistry curriculum since 1989. Driven in part by the lowest enrollments in the previous four decades occurring for the years 1993-1996, chemistry departments now permit students to enroll in Organic Chemistry as their first college chemistry course. The course begins with a thorough examination of the chemical structure of carbon-containing compounds in which the basic principles of orbitals and bonding, geometry and stereochemistry are discussed. The predictive properties of these compounds follow with emphasis placed on physical and spectral properties for isolation and characterization, although sensory effects that include taste and odor are beginning to be described in an increasing number of institutional courses. The energetics of chemical transformations focuses on combustion and acidity, and here the course introduces thermodynamic principles and the solution chemistry of weak acids.

Although older textbooks are still organized according to the functional groups of organic compounds, those introduced during the past four years have taken quite diverse approaches in order to capture the fragmented market. The newer textbooks are less then 1000 pages in length, and they can be purchased on protected diskettes that allow students to supplement textual materials with information obtained in lectures. Supplementary materials include the traditional problem solution manual, but, in what is perhaps the most striking innovation, special topics chapters are produced for specific institutions, either in textbook format or on diskette, to supplement the core topics according to the interests of individual instructors or programs.

The functional group approach for Organic Chemistry is, in the year 2000, employed for the first time in describing chemical reactions and their uses for synthesis. Fewer functional groups are described in this introductory course, and less time is devoted to the chemistry of aromatic compounds. However, biologically relevant molecules, especially carbohydrates, amino acids, and nucleic acids, are introduced early and integrated liberally within the course structure. The structures, properties, and syntheses of polymers are also integral components of this introductory course.

Gone from the Organic Chemistry course are many of the reactions that were previously described in virtually all Organic Chemistry textbooks. The Fischer Proof for the relative stereochemistry of monosaccharides can no longer be found in the newer organic textbooks. The preparation and reactions of sulfur compounds are now a special topics chapter. Oximes and hydrazones are also missing subjects. Greater emphasis is now placed on stereospecific reactions, and comparisons are made to enzyme controlled reactions. The use of plasmids for chemical synthesis is introduced as an emerging area for development at the interface of chemistry and biology.

In the Organic Chemistry Laboratory micro-scale organic methods are integrated into virtually all programs. Students routinely use capillary gas chromatographs with built-in integrators for their analyses of purity and GC/MS, FT-IR and FT-NMR for structural identification. As a result of the availability of this instrumentation, individual laboratory experiments rely less on simple organic compounds and, instead, employ more complex naturally occurring compounds and stereospecific reactions. Many institutions, by the year 2000, have integrated organic and inorganic chemistry laboratories into a course sequence in chemical synthesis.

Because of the changes in the chemistry curriculum that have taken place since 1989, the percentage of students who major in chemistry, which was 0.7 in 1995, is now 1.2. Enrollments in introductory courses are now 50 percent greater than they were in 1995. Employment opportunities in chemistry and chemistry-related areas, even with these increases, remain high.

 


References

[1] "Opportunities in Chemistry," G. C. Pimentel (Chairman), Committee to Survey Opportunities in the Chemical Sciences, National Academy Press, Washington, D. C., 1985.
[2] ACS Committee on Professional Training Annual Reports, Chemical & Engineering News.
[3] National Science Foundation, Science and Engineering Education Directorate, Washington, D. C.
[4] "Undergraduate Professional Education in Chemistry: Guidelines and Evaluation Procedures," American Chemical Society Committee on Professional Training, Washington, D. C.