Demonstrations in Advanced Courses Once every chemistry topic was accompanied by a demonstration. These served the dual purposes of illustrating the chemical point, and by adding color, emphasising the topic. Certainly some in-class experiments were done as well solely even in for entertainment value: there is a little hit of alchemist in all chemists. This ~ r a c t i e ehas largely . . disappeared - preliminary courses. Certainly the dryest are the theoretical courses in the upper years: a shame, as from both an entertainment and emphasis viewpoint some demonstrations are sorely needed here. In a theoretical graduate course or upper year class, mathematically sophisticated enough to handle the matrix treatment (or F operator) of nuclear magnetic resonance transitions, the plausible outline of the section of the course is as follows: several lectures introduction with the Az system, similar detailed analysis of the AB system and then perhaps the details of the AzB system if time permits. The F matrix treatment of the AzB predicts 8 strong lines around un and we and a single weak line near (2-A - we). These students are educated enough to predict from a simpler treatment only 5 lines and won't pay much attention to this extra line. At the conclusion of the last lecture on A2B a useful demonstration of matrix algebra "fact" is possible. Have your nmr technician search downfield for the "forbidden" line in a typical AzB such as 2,6-dichloroanisole. Instead of using offset, stick 4 or 5 pages of nmr paper together (containing only baseline) until the weak line and the strong lines are visible. I t is by the way a goad test of the theory and the instrument if the ninth line is seen. Unroll this long spectrum across the front desk as the period ends, demonstrating conclusively that the forbidden line exists. If your timing is good, the effect on the class is very dramatic! ~
~
T h e University of British Columbia Vancouver. B.C., Canada U6T 1W5
David E. B. Kennedy
Volume 52, Number 10, October 1975 / 653
