An inquiry-based experiment for the organic chemistry laboratory was developed to provide students with a cognitively rich research experience. Student teams were charged with optimizing the reaction conditions for the Williamson ether synthesis of 2-fluorophenetole from 2-fluorophenol, ethyl bromide, and potassium carbonate in either absolute ethanol or acetonitrile. Microwave acceleration of this SN2 reaction followed by rapid GC–MS analysis allowed students to review results, revise experimental conditions, and repeat the modified reaction and its analysis within a 3 h laboratory period. Variables that could be manipulated were reagent equivalencies, solvents and their volume, microwave reaction time, temperature, and wattage. Post-laboratory, all team data were available to the entire class for additional evaluation and each student was required to suggest new conditions for improvement in his/her laboratory report.

The laboratory is a mainstay in STEM education, promoting the development of critical thinking skills, dexterity, and scientific curiosity. The goals in the laboratory for nonchemistry, prehealth majors, though, could be distinguished from those for chemistry majors. In service courses such as organic chemistry, much laboratory time is often spent building discipline-specific technical skills that poorly align with the postgraduate goals of prehealth students. To address the needs of students in Muhlenberg College's organic chemistry course for nonchemistry majors, we developed a time- and resource-saving laboratory sequence that alternates traditional experiments with computer-graded self-guided inquiry activities. This innovative sequence requires approximately half the amount of reagents and fewer staff members, and it offers increased flexibility for students and instructors compared to a traditional (i.e:, weekly) lab experience. When this model was offered in 201315, student performances on reports, notebooks, quizzes, exams, and the ACS Organic Chemistry Exam remained consistent with grades in prior course iterations even though students spent less time in lab. Student feedback on this model has been positive, and students felt they were better able to focus on individual lab assignments. We present a detailed overview of this model along with direct and indirect assessment data.

Five reactions were rate-accelerated relative to the standard reflux workup in both multi-mode and mono-mode microwave ovens, and the results were compared to determine whether the sequential processing of a mono-mode unit could provide for better lab logistics and pedagogy. Conditions were optimized so that yields matched in both types of microwave ovens for a Diels-Alder cycloaddition, Wittig salt formation, Fischer esterifications, an E2 alkyne formation, and Williamson ether synthesis. Typically, a 10-fold rate acceleration was observed under mono-mode heating versus multi-mode heating, reducing the total run-time between 1.5 and 3.0 min per sample, which rivals the batch run-time of a multi-mode unit in similar to 16 student lab sections. Thus, the mono-mode microwave oven required a similar quantity of total reaction time in the lab, allowing students to run their experiments individually with less wait-time, competition for chemicals, equipment, and instrumentation and to complete the experiments in the lab period.

Microwave heating enhanced the rate of three reactions typically performed in our undergraduate organic chemistry laboratory: a Diels−Alder cycloaddition, a Wittig salt formation, and a Williamson ether synthesis. Ninety-minute refluxes were shortened to 10 min using a laboratory-grade microwave oven. In addition, yields improved for the Wittig salt and ether preparations. The Diels-Alder cycloaddition of N-phenylmaleimide and 1,3-cyclohexadiene in absolute ethanol in a closed vessel and 130 °C gave 84−90% yields. Formation of the Wittig salt, benzyltriphenylphosphonium chloride, from triphenylphosphine and benzyl chloride gave yields greater than 90% when heated in acetonitrile at 200 °C Yields doubled in the Williamson ether synthesis of 2-ethoxynaphthalene, from 2-naphthol, methanolic potassium hydroxide, and iodoethane with microwave heating at 130 °C.

endo-cis-N-Phenylbicyclo[2.2.2]oct-5-en-2,3-dicarboximide was synthesized by a Diels–Alder cycloaddition of 1,3-cyclohexadiene and N-phenylmaleimide in ethyl acetate. 1,3-Cyclohexadiene and N-phenylmaleimide were selected to illustrate the Alder rule, which reflects a preference for endo products and to overcome the difficulties associated with the traditional combination of 1,3-cyclopentadiene and maleic anhydride. This Diels–Alder reaction can be performed on macro- or miniscale, at room temperature for a week or under reflux for 2.5 hours to produce a 91% yield of a white solid that precipitates from solution and can be analyzed without further purification. Typical student results after 1.5 hours of reflux were 1.05 g (78%), mp 203.4–205.3 °C (lit. 204–206 °C). Results from IR and 1H and 13C NMR were consistent with literature values.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Ethylene Ketal Protecting Group Revisited: The Synthesis of 4-Hydroxy-4,4-diphenyl-2-butanoneMarsha R. Baar , Charles E. Russell , and Kristin L. Wustholz View Author Information Department of Chemistry, Muhlenberg College, Allentown, PA 18104Cite this: J. Chem. Educ. 2005, 82, 7, 1057Publication Date (Web):July 1, 2005Publication History Received3 August 2009Published online1 July 2005Published inissue 1 July 2005https://pubs.acs.org/doi/10.1021/ed082p1057https://doi.org/10.1021/ed082p1057research-articleACS PublicationsRequest reuse permissionsArticle Views2873Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Aromatic compounds,Ethyl groups,Hydrocarbons,Modification,Protective groups Get e-Alerts

There has been an increasing need, particularly in the pharmaceutical industry, to prepare chiral substances in single-isomer form. A chiral technique that makes an excellent introductory organic chemistry experiment is enantiomeric resolution. The classical resolution of (±)-mandelic acid using the chiral amine, (1R,2S)-(–)-ephedrine, was adapted for use in introductory organic chemistry lab curricula. (–)-Ephedrine and (±)-mandelic acid were reacted to produce diasteromeric ephedrinemandelate salts. The [(1R,2S)-(–)-ephedrine][(R)-(–)-mandelate] preferentially precipitated, was recrystallized, and analyzed by melting point, 168–170 °C (lit. 170 °C), 52% yield. The [(–)-ephedrine-][(–)-mandelate] was neutralized with 6 M HCl, extracted and rotary evaporated to produce a white solid in 32% yield whose melting point, 132–134 °C (lit. 133–134 °C), confirmed its identity as (R)-(–)-mandelic acid with a specific rotation of -135°, which corresponds to 85% optical purity.