A Chemistry Experience to Enrich High Achievers Mark Farrell LaRoche College, Pittsburgh, PA 15237 Raymond Pfeil Washington and Jefferson College, Washington, PA 15301 Albert A. Caretto Carnegie Mellon University, Pittsburgh, PA 15213 The Pennsylvania Governor's School for the Sciences provides an exciting enrichment exnerience in the sciences for very bright and talented high school students in Pennsylvania. The PGSS is a five-week summer school for Pennsylvania high school juniors and seniors and was initiated by the Pennsylvania Department of Education in early 1982. Carnegie Mellon University was chosen to host the school and there have been sessionsevery summer since 1982.The number of students participating in the program has increased gradually from 52 in 1982 to 90 in 1985. The five-week session is a residential program with activities planned for every day including Saturdays and Sundays. The goals of the PGSS, as defined by the Pennsylvania Department of Education, are to give an opportunity for highly talented and scientifically inclined high school students to engage in enrichment experiences in the sciences, to give them hands-on experience with up-to-date research equipment, to participate in specially designed courses in modern science, and to encourage . them to pursue technological careers. The various academic activities in which the students participate include core courses in molecular biology, organic chemistry, modern physics, discrete mathematics, and computer science. In addition, each student participates in a team research project in the area of his or her choice: biology, chemistrv. " oh&ics. . " . mathematics. or computer science. Although there are unique educational exper'iences in allwientilicareas, this repurt will he limited to thechemistryexperience. The Chemistry Core
The chemistry program consists of 17 h of a special course in organic chemistry, 24-30 h of special laboratory experiences in organic chemistry, and about 45 h devoted to the team reseaich projects. The students do not receive high school or college credit for any of the courses completed, nor do they receive grades for these courses and hence they do not compete against each other. Thus, the prime motivation-
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Journal of Chemical Education
alforce felt by these students is their innate desire to do well and to have a successful team research project. Reports of the team projects are published in the annual edition of the Journal of the Pennsylvania Governor's School for the Sciences. A typical day begins with courses from 8:30 a.m. to 1230 p.m. After lunch the student goes to the laboratory of his or her choice from 1:30 p.m. to 430 or 5:00 p.m. Most evenings are spent in attending elective courses, guest lectures, and occasionally, social events. After a week or 10-day adjustment period, the maiority of students thrive on this very demanding routine. In fact, as the program progresses most students spend all their free time on their team research project. Their enthusiasm is contagious and leads to a highly successful learning experience. The chemistry core course in simply entitled Organic Chemistry and is intended as an enrichment experience in selected topics of organic chemistry. The course assumes that the student has some basic knowledge of atomic structure and bonding and the onening session is a review of covalent bondingand electron dot molecular formulas. The course rapidly . . moves through orbital hybridization and the relationships between structure and physical properties. A1inhntic and aromatic hydrocarbons are di;;cu.sea as well as selected hydrocarbon derivations, e.g., alcohols and aldehydes. Sufficient IUPAC nomenclature is reviewed to allow a;easonahly articulate discussion of the basic reactions that occur. The fundamental thrust of the core course now turns to understanding organic synthesis. A basic theme of "what is it?", "how do we make it?" and "how do we know we made it?" is followed for the remainder of the course. Basic spectroscopy is discussed with special emphasis on infrared and nuclear magnetic resonance spectroscopy. A detailed study of selected mechanisms allows the student to understand how basic reactions occur. Rather than memorizing numerous and unrelated reactions, a detailed study of several reactions allows the student to gain insight into how changes in
molecular structure occur. A great deal of emphasis is daced on the structure of the intermediates in the-basic substitution and addition mechanisms. Through discussion in class and selected homework the student a limited but flexible "list" of reactions, which is then applied to synthesis problems. The point is not to examine all possible synthetic routes, or perhaps not even the "best" one, but to allow the student to ooerate as a molecular architect. Not onlv should the student 'design9'asynthesis but also should consider the details of how to isolate the nroducts and identifv them. Thus the student gains insight' into the job of the sinthetic chemist. The organic chemistry core course is an intensive look a t the structure of molecules and how to transform them. While some emphasis must be aimed a t basic memorization, much work is devoted to using the basic facts for problemsolving activities. The core course provides the nomenclature, mechanistic, and instrumental theory to allow the student to participate in the chemistry laboratory. While all PGSS students take the core course, only 15 to 20% will take the lab. The Lab Component
The chemistry laboratory a t PGSS is devoted t o the synthesis and characterization of derivatives of ferrocene. Ferrocene (dicyclopentadienyliron,(CjH5)-2Fe?7)was chosen, because over the last 20 years a great deal of literature on its toxicity has been generated. yet it remains novel enough that few high school students are familiar with its structure or orooerties. The nuroose of the chemistrv laboratorv is to allow 'the students' to'work with concepts and equi1;ment that are sienificantlv more advanced than those normallv found in a k g h schok environment. The students will work as organic synthetic chemists, preparing, purifying, and characterizing derivatives of ferrocene. Each experiment is designed to introduce new techniques and e q u i ~ m e nin t an evol;tionary approach which a1low.s each s u b ~ e ~ u eexperint ment to be a bit more soohisticated. (The basic techniques also lay the foundations-for the Chemistry Team ~ r o j k c t s that will be examined later.) The initial session involves a comprehensive safety program utilizing lecture, audio visual presentations, and laboratorv orientation. A uniaue feature of the lab is that two facult; members plus two dr three PGSS counselor-teaching assistants are present a t all times. This provides a teacherstudent ratio of one to four and allows for sophisticated work to oroceed safelv and smoothlv. The exoeriments alwavs demand that th;student think ahead andconsider alternatives but never a t the risk of creating confusion or danger. Rather than a series of interesting te;hniques presented in a series of unrelated exercises, the PGSS Chrrnistrv Lab provides asequential research project in which "toda;'~ product is tomorrow's reactant". The student is responsible for a three-step analysis of each experiment. Prior to each lab the student must flow chart the kev" exnerimental stens and look UD the toxicitv and . hazards of each new reagent. During the actual experiment all observations and results are recorded in ink in a hardbound notebook. After the lab each student must organize hisher results and write conclusions. Rather than using data report sheets with a "fill-in-the-hlanks" format, the student must summarize the day's work and decide what was actually accomplished. At each step of the synthesis the purity of the product is checked by melting point range and simple thin-layer chromatography. Infrared and ultraviolet-visible spectra are also obtained to confirm structural changes. The specific exercises done in the PGSS Chemistry Laboratory are sequential syntheses of acetylferrocene, l-hydroxvethvlferrocene. and vinvlferrocene. The initial svnthe" " sis involves the conversion of ferrocene to acetylferrocene by a Friedel-Crafts acylation using acetic anhydride. This exer-
Ase introduces the student to basic oreanic classware and such techniques as using steam baths anb vacuum filtration. After characterizing the acetylferrocene, it is converted to 1hydroxyethylferrocene by a sodium borohydride reduction. This experiment introduces magnetic stirrers and rotary evaporators to the student. The final experiment is the conversion of 1-hydroxyethylferrocene to vinylferrocene by a vacuum dehydration and sublimation procedure using ilumina. This procedure is particularly appealing to the students since they see the vinylferrocene crystals "grow" on the sublimator's "coldfinger". The actual series of compounds provide substances of greatly varied physical and chemical properties. The different groups attached to the cyclopentadienyl ring create easily interpreted infrared spectra and dramatic red and blue shifts in ferrocene's charge transfer bands. While these specific compounds are not necessary to achieve our objectives, trial and error has shown this sequence to be most effective. Team Projects
The team oroiects have evolved as extensions of the laboratory pordonuof the program. The students apply the theory obtained in the lecture course and the techniques mastered in the laboratory to an in-depth investigation of some aspect of the chemistry of ferrocene. The topics for the projects have been a combination of original research and adaptations of previouslv published work, although this fact is not made known to thi students. ~ a c topic h contains at least one key technique or method of analysis employed in a graduate-level synthetic organic chemistry laboratory. After a brief presentation of each topic outlining the goals of the oroiect and the exnerimental method to be emoloved. . - . the &dents band toget
