p-Quinodimethanes (p-QDMs) are reactive molecules that have been invoked as transient intermediates in a number of reactions. Dilute solutions of benzene-based p-QDMs, p-xylylene (1), alpha-methyl-p-xylylene (10), and 2,5-dimethyl-p-xylylene (11) can be prepared by fluoride-induced elimination of trimethylsilyl acetate from the appropriate precursor. It has been found that these solutions are stable enough to allow these reactive p-QDMs to be observed by 1H NMR spectroscopy at room temperature. For the first time, the 13C NMR spectrum of p-QDM 1 was observed. After several hours at room temperature, these p-QDMs form dimers, trimers, and insoluble oligomers. Formation of trimers provides evidence that p-QDMs 1, 10, and 11 dimerize by a stepwise mechanism involving dimeric diradicals as intermediates.

The Characterization and Analysis of a Product (CAP) project is used to introduce first-semester general chemistry students to chemical instrumentation through the analysis of caffeine-containing beverage products. Some examples of these products have included coffee, tea, and energy drinks. Students perform at least three instrumental experiments as a part of this five-part project to analyze different components of the beverage and its packaging. In this discussion, the first of these experiments is presented. Caffeine and other components, such as flavorings, are extracted from the product using dichloromethane. The extract is analyzed using thin-layer chromatography (TLC) and gas chromatography−mass spectrometry (GC−MS) to identify caffeine and other trace components. Students also calculate the percent abundance of the 35 Cl and 37 Cl isotopes from the dichloromethane mass spectrum. These exercises demonstrate several basic concepts introduced in the first-semester course, and are easily adaptable to using in several courses in the undergraduate curriculum.