Curriculum and Experiments in an Organic Honors Laboratory A Model for Parallel Honors and Regular Sections Norbert J. ~ienta,'Craig Regitz, Joseph Richards, and Thomas N. Sorrell The University of North Carolina, Chapel Hill, NC 27599
The ability to offer honors sections in a large laboratory program provides a number of opportunities as well as challenees. The recent advent of honors sections in both semesters of introductory organic chemistry laboratory here have led to a svstem that we have devised for the sec--ond semester. We sought a series of experiments that would, at least in part, parallel those done in the regular sections but with an appropriate increase in independence and challenge for those receiving honors credit. A concern about simply using "cookbook" procedures in organic laboratories has been expressed previously in a commentary ~ 2 plan offers an alterand challenge hy ~ l c k e r i n ~ d Our native that mav be auite ecnerallv a~plicable.Our solution -is to allow the honors sections d&elop new procedures for subsequent use by the regular sections. Our experiences on how to accomplish this are described herein. After completion of one year of general chemistry, the typical student enmlls in two lecture courses, introductory analvtical rChem. 41: "Modern Analytical Methods for Separation and Characterization," 3 &edit hours) and introductory organic I (Chem. 61,3 credit hours). Those two lecture courses are the co- or prerequisite for a one-credit hour laboratory (Chem. 41L: "Laboratory in Separations and Analytical Characterization of Organic and Biological Compounds"). The second-semester sequence includes introductory organic I1 lecture (Chem. 62, 3 credit hours) which is a co- or prerequisite for the one-credit hour lab (Chem. 62L: "Laboratory in Preparation and Characterization of Organic Compounds"). This latter laboratory course is the focus of attention here.
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Choice of Experiments It was our intention to focus both honors and regular sections of Chem. 62L on performing reactions. All students would have seen many examples of organic transformations in the lecture course, and we hoped to provide them with analogous experimental opportunity. Separation and characterization (e.g., extraction, gas chromatography,liquid chromatography, thin-layer chromatography, electmphoresis, gel permeation chromatography, and uv-visible spectrophotometry) are part of the first-semester course (i.e., Chem. 41L). As a result, we felt that we could wncen-
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trate primarily on the reactions in addition to some spectroscopy and handling and manipulation techniques. Concurrent with the initiation of honors laboratory sections. we made the decision to reduce the scale of materials usedand adopted microscale glassware (i.e., a modified kit of the Williamson type available from Kontes). As a result, the honors some insizht into the kinds of .----~ - - section ~ - ~ ~rovided difficulties student; might have with &e new glassware in addition to questions dealing with the experimental content itself. No problems were uncovered with the transition in glassware, although the minimum quantities of chemicals that are used need to be sufficient (150-200 mg) to assure success in the hands of those with limited expertise. The reactions that were examined in this way by the honors sections are given in the first column of the table. ~~~~
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The Participants Students who take organic chemistry here have either begun a major in the College of Arts and Sciences or are completing the second of a two-year stay before moving on to any of a number of professional programs (e.g., pharmacy, medical technology, etc.). Chemistry offers only a single sequence for all students in general and organic chemistry (two semesters each), but each level provides an honors option. Enrollment in organic honors lab (Chem. 62HL) requires permission of the instructor, a GPA of 3.0 (out of 4.0), and approval of the College Honors Program. It is not necessary to enroll in the honors section of the lecture course(s)to be admitted to the honors lab. The normal spring enrollment for regular organic laboratory sections is about 500, and Honors was limited to four sections of about 14 each (Monday through Thursday afternoon). Each section was directed by a graduate teaching assistant, chosen on the basis of experience with lab techniques and in dealing with students. A head teaching assistant, responsible for the daily operations of all sections, was available during the lab to solve problems and acquire materials not anticipated during setup. A faculty instructor and the director of laboratory development constituted the moup. remainder of the decision-makine .... . All of the management personnel met once a week to review the previous week and vlan future itratwies. The teaching assistant from ~ o n d passed a ~ practical information t o t h e one in charge of the next day, and so forth. This system seemed to be the simplest and the best one conceived to assure reasonable success by the end of the week.
Volume 70 Number 10 October 1993
841
Parallel Honors and Reaular Sections Laboratory ~ x ~ & i r n e &
Spring 1991, Honors components from a Mixturea B. Crystallization of an Unknowna C. NucleoDhilic ~ubstitut/on: Svnthesis of
Spring 1992, Regular
Spring 1992, Honors
same as
same as Ab,C
same as Bb,C
same as
same as Cb
same as Cb
D. Electrophilic same as Db Aromatic Substitution: Nitration of 4-Methyla~etaniiide~.~ E. sodium Borohvdride E. Sodium Reduction of Borohydride Reduction of 2-Octanoneb same as Fb F. Preparation of Amides from Carboxylic~ c i d s " ~ same as Gb G. Oxidation Reactions of Benzylic Alcoholsb H. A Mixed Aidol same as Hb Condensationb same as lb I. Epoxidation of transStilbeneb same as Jb J. lodoform Reactionb same as Ke K. Spectroscopy Problemse
same as Db
same as previous columnb same as Fb same as Gb
Laboratory Organization A syllabus, organizational notes, and a schedule were given to each student. A textbook oriented toward the performance of techniques and methods was required (3,. Each section of 14 was divided into groups of three to four students. Each p u p was assigned a different experiment or a differcnt v&ahle (e.g., starting material) for a common reaction. In addition, each w u p was given some lead references a week or two prior to the scheduled experiment. The references included: (1) laboratory manuals from ren no us vears that had been produced in-house but involved large amounts of materials or I 2, pruwdures From general texts (4-6, or the literature. Soecllic c~tationsfrom the literature were given in order to iimit time outside of lab that would be required in the library. The students were instructed to find procedures that were appropriate for their laboratory and introductory organic chemistry in general. Each group was charged with adjusting reaction parameters (i.e., small changes in amount or stoichiometrv. temperature. time. solvent. isolation, and purification &ndi
