Abstracts of papers presented at the
31st Central Regional ACS Meeting, June 20-23, 1999
- Enough is as good as a feast: organic chemical pedagogy and the theory of bonding
- by Daniel J. Berger
While chemical bonding theory is the delight of physical organic chemists, it is both dreaded and misunderstood by students because of the multiplicity of bonding models offered. Unfortunately, this multiplicity of models corresponds to the actual discussion of bonding among chemists! I propose that we as teachers take a consciously graduated approach to chemical bonding theory, and will present a plan I have used in teaching organic chemistry.
- Modeling unusual molecules with semi-empirical calculations
- by Daniel J. Berger and Peter P. Gaspar
Unusual molecules, either highly reactive species or molecules with unusual bonding patterns, can be adequately modeled with semi-empirical methods in a small fraction of the time required for ab initio methods. Semi-empirical modeling has been unjustly neglected in the past several years, and a reminder of its utility seems appropriate.
Semi-empirical modeling is useful pedagogically because of the time saved, but can also find a place in support of experimental research. Several examples will be presented of the modeling of unusual molecules with low-level calculations, and the strengths and weaknesses of the methods will be discussed. A comparison of results of low-level calculations with DFT results reported elsewhere (Apeloig, 1997) will be made for bis(triisopropylsilyl)silylene.
- Efficacy of Group Learning in First-Semester Organic Chemistry as Measured by Student Surveys
- The results of student surveys will be presented, bearing on a first use of in-class "guided inquiry" as modeled by Roy Butler's organic chemistry course at Norwich University. These surveys give Bluffton College student perceptions of the value of the approach. Examples of the "guided inquiry" worksheets will be presented. A preliminary analysis of student achievement will be given, based on examination results.
- Problem-based experiments for the organic chemistry laboratory
- Descriptions of a number of problem-based experiments for the "sophomore" organic chemistry laboratory will be given, and their efficacy assessed based on student performance (as compared to "cookbook" experiments) and a limited number of student surveys. Problems set for students include using molecular models to determine the most likely site for nucleophilic attack; finding and explaining trends in keto-enol equilibria; identification of unknown compounds from spectroscopic information alone; and identification of the primary products of a Friedel-Crafts alkylation reaction. Most of the problems do not involve group analysis, though the students may be asked to pool their data and occasionally they collect the data in small groups.
- An organic electrochemical experiment for the first-year laboratory
- A simple, microscale electrochemical synthesis for the first-year organic chemistry laboratory will be presented. While products are not isolated, GC analysis provides the student with the information needed to assess the efficiency of the electrochemical process. Results from the first group of students to use the experiment will be presented.