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An undergraduate laboratory experiment in organic chemistry should include interesting organic synthesis and the resolution of a tricky problem related to the synthesis. The second part is important to encourage students' involvement in the experiment. Both parts play a major role in the experiment described in this paper.
With modern spectrometers and the development of new techniques, NMR has evolved into one of the most useful tools available to students in chemistry for investigating structural or mechanistic problems (1). Some examples of potential uses have been described in this Journal (2). This experiment introduces students to the main concepts of two essential NMR techniques for molecular structure investigation. Heteronuclear multiple bond connectivity (HMBC) and proton-coupled 13C NMR are used to determine the isomer formed in a regiospecific reaction. The study, based on long-range coupling between quaternary carbons and protons on neighboring carbons, is presented step-by-step with didactic progression. In addition, the regiospecific reaction provides an excellent example of ring-opening in a monosubstituted cyclic anhydride. Nucleophilic attack on carboxylic acid derivatives and problems of regioselectivity are also...