Claude H. Yoder Franklin and Marshall College Lancaster. Pennsylvania 17601
I
Synthesis in an Integrated Curriculum
In 1966, with financial support from Research Corporation, the chemistry department of Franklin and Marshall College began the design of a new curriculum. The result of the twovear studv was a curriculum based uoon maior conceots rather than the historical divisions of inorganic, organic, analytical, and physical chemistry. The concepts selected to provide the framework of the curriculum were structure, bonding, rate of reaction, and extent of reaction. As indicated by the course titles given in Table 1, these topics are introduced a t an elementary level in the first-year course. This is followed in the second-year by a more detailed examination of rate and mechanism with a natural emphasis upon reactions involving organic compounds. In the third year the level of sophistication increases and the four topics are treated in considerable mathematical detail in ~xte't and Rate of Reactions (Thermodynamics and Kinetics), Bondiw and Structure (Elementary Quantum Mechanics and ~ ~ e c t r o s c o ~and y ) ,Electrolyte Solutions (Ionic Equilibria and Electrochemistry). The fourth junior year course is discussed below. In the fourth year the topics are examined again a t an elevated conceptual and mathematical level in Reactiuity Models and Symmetry, Stereochemistry, and Group Theory. There is also a Topics course and an Advanced Ex~erimentationlaboratorv course that provide a degree of flexibility to the curricul~m.The courses required for a major in chemistry are Chem 1through Chem 38, Chem 49, and one course selected from Chem 43 and Chem 44. Independent Study is strongly encouraged and about half of the approximately 30 senior majors avail themselves of that opportunity. Thus, the curriculum is structured in spiral fashion with the same major concepts heing covered in three levels of increasing sophistication. The first level includes years one and two and is descriptive in nature rather than mathematically sophisticated. The second level, year three, is more quantitative and mathematical, while the third level, year four, is a t the most rieorous conceotual level. Throughout most of the curriculum inorganic and organic compounds are treated in parallel fashion. For example, in the introductory course the nomenclature, bonding, structure, isomerism, and acid-base reactions of hoth inorganic and organic compounds are discussed; in the senior year Reactiuity Models course, suhstituent effects, acid-base models and other reactivity models are examined for both inorganic and organic compounds. The major exception to this integration occurs in the second year where, as mentioned above, there is a definite emphasis on the reactions and reaction mechanisms of organic compounds. The concepts of physical and analytical chemistry are also woven thron~houtthe curriculum. For examnle., methods of classical quantitative and qualitative analysis are taught in the first- and second-year courses and in the third-year course on Electrolyte Solutions; spectroscopic methods of analysis are introduced with colorimetrv in the first-vear course and continued with spectroscopic ihentificationmethods in the second vear and auantitative soectroscooic analvsis and s t r u c t u r ~determination in the t'hird yea; electroEhemica1 methods are discussed primarily in Electrolyte Solutions. Of course, most of the traditional concepts of physical chemistry appear in the iunior-vear courses Extent and Rate of React h i s and Bonciing and Structure. Each course in years I, 11, and 111 has a four hour per week
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572 / Journal of Chemical Education
Table 1. Year I
IV
Semester I I
Semester I
Chem 1 Structure and Comwrition Chem 2 of Matter
I1 Chem 3 Ill
The Chemirtrv Curriculum
Introduction t o Rate of Reaction and Mechanism
Chem
Chem 35 Extent and Rate of Chemical Reaction
Cnem
Chem 37 Bonding and Structure
Chem
Chem 4 3 Topics in chemistry
Chem
Chem 49 Reactivity Modell
Chem
Introduction to Chemical Reactions 4 Reaction of Carbon Compounds 3 6 Chemistry of Electroivte S0l"tiOnr 38 Svntherir and oetermination of Structure 44 Symmetry. StereOchemirtrY and Grouo iheory ' 4 7 Advanced Experimentation
Chem 90alndewndent Study aCan be taken for not less than two semesters.
laboratory portion which consists of projects designed to teach the methods of modern experimental chemistry. The projects are generally unrelated to the lecture portion of the course except that whenever possible the theory necessary for an understanding of the project has preceded the project. Several typical projects have been described previ~usly.l.~ Synthesis and Determination of Structure The integrated nature of the curriculum hopefully facilitates the svnthesis of a varietv of exnerimental and theoretical details. This "pulling together" bf concepts and facts is especially apparent, however, in the fourth junior-year course entitled Synthesis and Determination of Structure. This course grew out of a need for a vehicle for applied .. thermodvnamics;separation methods, and a greater amount of work in spectrometric methods of structure determination. Since the process of synthesizing chemicals involves all of these topics and because, moreover, the synthesis of compounds is such a unique and important part of chemistry, a course in Synthesis was created. As indicated in Table 2 the course is divided into five main parts. The first deals with the choice of synthetic route from a consideration of the thermodvnamics and relative rates of pussi1)le routes. The emphasis is primarily on the calculation methods. of AH" and A(;" hv 1)oth"exart" and anuroximate .. Examples are drawn from previous laboratory projects and reactions of commercial or synthetic value. In the second part, the reaction conditions-temperature, solvent, pressure, mode of addition, mole ratios, concentrations, eW.-are determined fur the particular rmction rhosen fur a s\mthcsis. Methods of separation an: treated in the third part 4 t h emphasis on the choice of the best technique for the separation of a given set of compounds. The fourth section deals with methods of identification: the use of elemental analyses, chemical tests such as solubility and 'Snavely, F. A., and Yoder, C. H., J. CHEM. EDUC., 48, 621 (1971). 2Suydam, F. H., and Yoder, C. H., J. CHEM. EDUC., 48, 849 (1971).
Table 2. Outline for Svnthesis and Determination of Structure
~
II
iii
iV
V
~
6. ~pp;&imata calculations for reactions involving covalent compounds: bond energies. AHvap, group contribution9 7. Application of thermodynamcir t o reactions involving covalent compounds 8. The hard-soft acid-bare principle B. Kinetic considerations 1. Thermodynamic versus kinetlc control 2. The Hammond postulate 3. The Hammett eouation 4. Effect o f roiveni 5. Cyclizationl Determination of Reaction Conditions A. Choice of solvent, temperature, mode o f addition, concentrations i;cDmpetitiw reactions The Separation A. Techniques based on phase changer; dirtiliation, sublimation 6 . Techniauer bared on relative rolubiiitier: recrystallization. extraction C . Chromatographic techniques: adsorption, partition, ionexchange, exclusion Determination of Structure A. Use of elemental anaiyrer and molecular weight 6.Chemical methods: solubility tertr, classification tertr C. Spe~trolcopicmethods 1. Uitra~ioiet-visible:transitions, effect of structure, solvent effects 2. infrared: single orciiiatorr, effect of structure, coupling 3. Nuclear Magnetic Resonance: theory of chemical shifts. coupling. nuclei other than 'H. line shape 4. Mass ~ P ~ C ~ ~ O ~ Cdetermination O P Y : of molecular fotmula. fragmentation patterns m a i v s i s o f Selected Svntheres and Svnthetic Methods
classification tests (for both inorganic and organic compounds), and, especially, spectroscopic methods. The ohjectives of this part are twofold: first, to develop a facility for the identification of compounds (structural formula) from
chemical and spectroscopic data, and second, to provide the concepts necessary for the determination of structural detail (geometry, bond angles, etc.) from readily available instrumentation such as uv-vis, ir, and nmr spectroscopy. In the final section, a series of selected syntheses are analyzed from the standpoint of thermodynamic and kinetic feasibility, stereochemical design, reaction conditions, isolation procedures, and product identification. During the past year the syntheses chosen-harreleue, borazaronaphthalene, and the annulenes-were related by the general theme of aromaticity. Because the course is taken in the second semester of the student's junior year, it reviews and builds upon the organic reactions and mechanisms and spectroscopic identification presented in the second year, and the principles of thermodynamics, kinetics, wave mechanics, and spectroscopy presented in the first semester of the third year. I t also brings into focus many aspects of the first-year course: principles of structure, acid-base reactions, use of electrode potentials, solubility rules, separation and identification of ionic compounds, etc. The use of lahoratory projects as examples provides a fresh understanding of the techniques and reactions involved in laboratories past and present. No single text has been found suitable for the course. In most of the four years in which the course has been given only a text such as Dyer's Applications of Absorption Spectroscopy of Organic Compounds was used for the routine aspects of spectroscopic identification. Lectures are supplemented by references to the literature and by eight to ten problem sets. Student reaction to the course has been favorable. Comments such as "ties everythingtogether" reflect a t least partial success in the integrative objectives of the course. In addition to learning many new concepts and applying old ones, the students also seem to gain an appreciation for the value of thermodynamics and spectroscopy and for the great art of synthesis.
Volume 54, Number 9, September 1977 1 573
