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A Novel Preparation for the Undergraduate Organic Chemistry Laboratory Course
Keith F. McDaniel* and R. Matthew Weekly
Department of Chemistry, Ohio University, Athens, OH 45701
The ideal undergraduate organic chemistry laboratory experiment involves several important components. These components include the examination of one or more interesting and historically important reactions to provide an interesting organic molecule, stimulating yet challenging 1H nuclear magnetic resonance (NMR) and infrared (IR) spectroscopic data analysis, and a straightforward and consistently reproducible experimental procedure that can be completed within a typical laboratory time frame. In addition, an element of the unknown is important, to allow student input into the experiment and avoid the cookbook aspect of many typical undergraduate laboratory experiments. An experiment that has been carried out in our organic laboratory course for the past several years contains each of these components, as it involves both a Diels-Alder reaction and the ring-opening of a cyclic anhydride, ^sup 1^H NMR data that allow utilization of both 1-D and simple 2-D experiments, and formation and isolation of an analytically pure crystalline product within one hour.
The Diels-Alder reaction clearly is one of the most important organic reactions taught to undergraduate organic chemistry students, and most undergraduate organic textbooks contain sections on the reaction's mechanism, stereochemical outcome, and overall scope and limitations (1). The most common Diels-Alder reaction carried out in undergraduate organic chemistry laboratories involves the reaction between cyclopentadiene and maleic anhydride (2). Although this reaction works quite well and generates a product that is isolated easily, cracking of the cyclopentadiene dimer is a nuisance, and the product generated by this reaction gives a 1H NMR spectrum that is difficult for students to analyze completely.
Another important topic in all undergraduate organic chemistry textbooks is the addition/elimination reaction of carboxylic acid derivatives (3). Nucleophilic attack on anhydrides, acid chlorides, esters and amides typically is examined, and interconversion of these functional groups is presented. Most undergraduate organic chemistry laboratory texts contain simple esterification reactions and often acylation reactions of amines, such as aniline (4). An experiment involving the ring opening of a cyclic anhydride, in concert with a Diels-Alder reaction, would be a useful alternative to these reactions.
The reaction of equimolar amounts of trans,trans-2,4hexadien-1-ol (1) and maleic anhydride (2) in...