Developing and Implementing Multioutcome Experiments in

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Developing and Implementing Multioutcome Experiments in Undergraduate Teaching Laboratories To Promote Student Ownership of the Experience: An Example Multioutcome Experiment for the Oxidation of Alcohols Kasey L. Yearty, Caroline E. Glessner, and Richard W. Morrison*

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Department of Chemistry, The University of Georgia, 140 Cedar Street, Athens, Georgia 30602-2556, United States S Supporting Information *

ABSTRACT: Single-outcome experiments are used in the undergraduate instructional laboratory, particularly for large lectures associated with multiple sections of instructional laboratories, due in large part to efficiencies associated with chemical purchases, experiment preparations, and assessments. Despite the practical advantages, single-outcome experiments are not effective in encouraging students to critically analyze and interpret their acquired individual results. Instead, students are satisfied if their results are the same as or similar to all of their classmates’ results, limiting the opportunity for engagement with the laboratory content. In contrast, multioutcome experiments (MOEs) require students to explore the same chemical reaction or transformation but obtain individual results. Individualization of results is accomplished by using a set of starting materials or reagents, one of which is assigned to each student. Students do not know the identity of the assigned component but may be given possible options for its identity. Students elucidate the identity of their individualized products, using modern analytical techniques such as gas chromatography, Fourier-transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy, and deduce the unknown component of their experiment. An example MOE for the oxidation of alcohols is described herein. A traditional single-outcome experiment that utilized a common household oxidizing agent (hypochlorite bleach), rather than a heavy metal-containing alternative, was modified. For the MOE modification, one unknown secondary alcohol (2-pentanol, 3-pentanol, or 3-methyl-2-butanol) was oxidized using bleach. Each student pair was assigned one of three possible unknown alcohols, all of which were constitutional isomers of secondary alcohols. Students knew the identities of the three possible alcohols. Analysis of their oxidation products was accomplished using FTIR and benchtop 1H NMR spectroscopies. Students interpreted their spectra and deduced the identity of the unknown alcohol they were assigned. This experiment provides a tangible framework to understand the applicability of the oxidation reaction and the utility of FTIR and 1 H NMR spectroscopies. KEYWORDS: Second-Year Undergraduate, Organic Chemistry, Inquiry-Based/Discovery Learning, Alcohols, NMR Spectroscopy



BACKGROUND Students must be guided in both theory and practice to successfully master chemistry. Broadly speaking, theoretical and conceptual exposure and development have historically been the province of the lecture presentation, whereas practical techniques and data analysis have been associated with the instructional laboratory. Recently introduced pedagogies such as guided-inquiry and flipping the classroom have successfully modified lecture presentations.1−6 While progress has been made in the development and implementation of inquiry-based and discovery-based laboratory experiments, modifications to the expository laboratory have been more difficult to implement.7−15 As a result, the experimental techniques and data analysis students learn in expository laboratory exercises seem to be increasingly unrelated to the theoretical and conceptual learning objectives introduced in lecture. One of the primary reasons for this disconnect is the limitations of single-outcome experiments. A traditional singleoutcome experiment requires all students in an instructional laboratory to perform the same experiment, thereby obtaining the same anticipated result.16,17 The variations observed in student results were mostly associated with their experimental © XXXX American Chemical Society and Division of Chemical Education, Inc.

techniques. Percent yield calculations, melting points, endpoint determinations, and other common analyses determined their success. Assessments based upon these metrics were tenuous. Students could perform these “cookbook-style” verification experiments and obtain results without understanding the underlying concepts and theory.18 Modifications to the single-outcome experimental paradigm are necessary to individualize experiments and thereby encourage students to become more invested in experimental procedures and results. However, there are significant challenges associated with developing individualized experiences in the instructional laboratory. The first and most important factor is safety. All changes must be limited to chemicals and procedures that do not present any significant dangers to inexperienced students. The second challenge to modifying single-outcome experiments is that experiments must be designed to have high success rates. Most single-outcome experiments have been Received: March 11, 2019 Revised: July 24, 2019

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DOI: 10.1021/acs.jchemed.9b00212 J. Chem. Educ. XXXX, XXX, XXX−XXX

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and ownership of the experiment.13,14,21−25 Commonly used NMR instruments have high operation costs, requiring the use of cryogens and specially trained staff members. Since the advent of benchtop 1H NMR technology, spectra of neat samples spiked with tetramethylsilane (TMS) are collected in a matter of seconds and processed within a few minutes using NMR processing software such as MestreNova or TopSpin. The ability to quickly acquire spectra without deuterated solvents or NMR tubes is advantageous for high enrollment UCLCs. There are several examples in the literature that incorporate this technology in the undergraduate setting.26−28 Benchtop NMR has significantly and positively impacted MOEs by increasing student ownership of experimental results and familiarizing students with NMR as an essential analytical technique. The researchers first introduced a MOE in this Journal in early 2017.28 Since then, numerous MOEs have been developed and implemented at UGA. In the current order of the curriculum, the oxidation of alcohols MOE followed MOEs previously incorporated into the organic chemistry curriculum. After each experiment, students had the opportunity to participate in a postlab survey to earn extra credit on the associated postlab report.

optimized to achieve consistent, reproducible results. In a research setting, the apparent failure of an experiment can be quite informative in planning and modifying future experiments. However, the failure to achieve a positive result from an experiment in an instructional laboratory is problematic due to the difficulty and time involved in troubleshooting the problem, identifying the cause, and subsequently modifying the experimental procedure to achieve the desired result. A third constraint that shapes the development of experimentation in the instructional laboratory is time. The array of potential experiments is limited to those that are accomplished within the traditional 3 h laboratory period. No transformations or analyses are considered for implementation that require a 6 h heating period or monitoring beyond the time scheduled for the instructional laboratory period. Product characterization must also be accomplished in this same time frame. A fourth consideration is the cost associated with purchase and disposal of chemicals. It is necessary to develop experiments that are performed with inexpensive materials and that generate waste that is easily and inexpensively remediated. In summary, to make experimentation in the instructional laboratory more efficacious, experiments must be developed that encourage individual comprehension of theory and mastery of techniques. In addition, these experiments must also be cost and time effective, safe, and consistently reproducible. These are nontrivial challenges that have delayed the implementation of new experiments to the current body of traditional experiments.



EXAMPLE MOE: OXIDATION OF ALCOHOLS At UGA, traditional oxidation of isoborneol to camphor was performed.29,30 The researchers modified this standard singleoutcome experiment to incorporate the use of multiple secondary alcohols as unknown reagents in the oxidation of alcohols to ketones (see Figures 1 and 2). The oxidation of



MULTIOUTCOME EXPERIMENT A solution to the aforementioned challenges that we have developed at the University of Georgia (UGA) Chemistry Department is the implementation of multioutcome experiments (MOEs). A multioutcome experiment is designed to increase the individualization and student ownership of their laboratory experience and to reinforce concepts taught in the associated lecture course. A successful MOE must have a component that can be varied, appropriate purification methods must be available to address the differences in stoichiometric ratios of the possible unknowns, and the resulting products must be distinguishable using analytical tools available in undergraduate chemistry laboratory courses (UCLCs). For experiments developed at UGA that utilize benchtop hydrogen-1 nuclear magnetic resonance (1H NMR) technology, these last two challenges are the most significant due to the difficulty in finding a variety of reagents that exhibit similar reactivities and yield products that can be distinguished on a low-field NMR instrument. In practice, an unknown reagent is introduced early in an MOE. Students, individually or working in pairs, complete the same procedure as their classmates. Numerous unknown reagents are used, which lead to variances in observations, data analyses, and results. Compared to traditional single-outcome procedures, the aforementioned variances allow more unique learning experiences to occur in the classroom and create a more synergistic relationship with the associated lecture presentation.16,17,19,20 An example of an MOE recently developed and implemented into the undergraduate organic instructional laboratory explores the oxidation of alcohols. This new MOE addresses the challenges previously mentioned and also specifically reinforces the utility of NMR spectroscopy by providing access to benchtop 1H NMR technology to undergraduate students, thereby encouraging engagement

Figure 1. Reaction scheme provided to students. R can be R′ for the unknown secondary alcohol and corresponding ketone.

Figure 2. Potential secondary alcohols provided to students as the unknown component. Students knew the identities of these three alcohols but did not know which alcohol they received during the laboratory period.

alcohols using reagents such as household bleach was reported previously in the literature.14,31−36 However, the development of a multioutcome experiment for the identification of an unknown alcohol with inclusion of benchtop 1H NMR analysis has yet to be reported.



EXPERIMENTAL METHODS When completing the previously mentioned single-outcome oxidation experiment, student experiences and results were uniform with respect to their observations, data analyses, and the resulting white powdery product. In this new MOE, adapted from a single-outcome procedure described by Mohrig and co-workers, students were provided with one of three unknown secondary alcohols.37 One important aspect of the B

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three unknowns in this experiment is that 2-pentanol, 3pentanol, and 3-methyl-2-butanol are all constitutional isomers and, therefore, have the same molecular weight. This benefit made the purification process easier to streamline because it was not necessary to consider stoichiometric excess for any of the unknown alcohols. Utilizing a low-cost, household oxidizing reagent (hypochlorite bleach), these unknown alcohols were oxidized to the respective ketones and analyzed using Fourier-transform infrared (FTIR) and benchtop 1H NMR spectroscopy. A 2.1 g scale for the unknown alcohol was used for this MOE to prepare sufficient quantities for a subsequent MOE studying the reduction of aldehydes and ketones. Initially, the oxidation MOE was implemented in the Spring 2018 sophomore Advanced Organic Chemistry II laboratory course, a course composed of Honors students and chemistry majors. During this beta test, 50 students completed a postlab survey (see Supporting Information Survey 1). After Spring 2018, two additional trials of the experiment were performed in the sophomore Organic Chemistry II laboratory course, which typically has a higher enrollment than the advanced section. It is of note that the Spring 2018 iteration of the experiment included double the volume of dichloromethane (ten milliliters per portion) during the extraction segment of the procedure. This volume was reduced by half (five milliliters per portion) during the subsequent iterations to minimize solvent use.38 During the Summer and Fall 2018 iterations, 336 students completed the same postlab survey. The survey was administered to monitor the students’ identifications of their unknown secondary alcohols and percent yields. The survey asked students to rank, in decreasing order, the usefulness of several identification tools at their disposal during the experiment and to provide a brief justification for each response. In addition, students self-reported their confidence levels for correctly identifying the unknown based solely upon analysis of the 1H NMR spectrum and without the 1H NMR spectrum. Finally, students were provided the opportunity to leave further feedback regarding the experiment, if desired.

Table 1. Identification of Unknown Secondary Alcohols by Students Unknown Secondary Alcohol 2-pentanol 3-pentanol 3-methyl-2-butanol Course and Semester Advanced Org. Chem. Spring 2018 Organic Chem. II Summer 2018 Organic Chem. II Fall 2018 Total

Number of Students Correct

Number of Students

106 107 121 Number of Students Correct

126 119 141 Number of Students

Correct, %

50

50

100

81

90

90

203

246

83

334

386

87

Correct, % 84 90 86

in Supporting Information Figures 1−5. A complete breakdown of student identifications of unknown secondary alcohols is included in Supporting Information Table 2.



DISCUSSION In this experiment, students successfully oxidized secondary alcohols into ketones using household bleach and analyzed their products using FTIR and 1H NMR. Students were thus provided with the opportunity to apply the spectroscopic analyses taught in the associated lecture course to a product that they made in the laboratory. On average, the Spring 2018 students reported the mass of their final product as being 1.453 g (71%) for 2-pentanone, 1.348 g (66%) for 3-pentanone, and 1.203 g (59%) for 3-methyl-2-butanone. Overall, this was an average of 1.326 g (65%) for all unknown secondary alcohols combined, thereby producing ample product for characterization and for subsequent implementation of the corresponding reduction experiment. The masses of the final products decreased when the volume of dichloromethane was reduced by 50%, as indicated in the Methods section. For example, during the Fall 2018 iteration, the average masses of products were 0.943 g (45%) for 2-pentanone, 1.252 g (60%) for 3pentanone, and 1.083 g (52%) for 3-methyl-2-butanone. In other words, although the students began with 2.1 g of the alcohol, less product was recovered as a result of the reduction in the volume of the extraction solvent. This was an undesirable result because of the need to prepare sufficient quantities of the oxidation product for both characterization and for use as starting materials for the subsequent reduction MOE. Therefore, the reduction in the volume of dichloromethane used may be most useful if students are not collecting the product for use in a subsequent experiment. In the postlab survey, students ranked the usefulness of several tools in determining the identity of their unknown secondary alcohol. For all iterations, the most useful, second most useful, and least useful identification tools were reported as 1H NMR spectroscopy, FTIR spectroscopy, and color, respectively (see Supporting Information Figures 6−11). While the ketones were all the same color, the “color” option has been traditionally incorporated into the postlab survey so that the survey is standardized with postlab surveys for other MOEs, which have been developed by the researchers. The researchers also asked students to elaborate on their responses, thus encouraging them to critically analyze their spectra in comparison to the spectra of their peers. One student stated, “The specific integration numbers in addition to the chemical



HAZARDS Safety glasses, lab gloves, and lab coats must be worn at all times. Sodium hypochlorite is the active ingredient in household bleach and will bleach colored clothing. Acetic acid and sodium hypochlorite are irritants and should be washed away immediately if in contact with skin or eyes. Use caution when working with 6 M sodium hydroxide as it is caustic and may cause burns. Dichloromethane is highly volatile. Avoid sparks, flames, and hot surfaces. Take care when dispensing and evaporating it. Avoid vapors and make sure that the snorkels (fume removal arms at each student lab station) are turned on and functioning properly before dispensing any liquids. Any vapor or liquid exposure should be reported to the teaching assistant (TA) immediately. Dispose of all liquid waste in the appropriately labeled bottle in the lab hood. A table with more specific information about the reagents used is available in Supporting Information Table 1.



RESULTS For the Spring 2018, Summer 2018, and Fall 2018 semesters, 334 out of 386 students (87%) who participated in the postlab survey correctly identified the unknown secondary alcohol (see Table 1). Example student spectra are provided in Figure 3 and C

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Figure 3. Sample 1H NMR spectrum of 3-methyl-2-butanone from the 82 MHz picoSpin benchtop 1H NMR. The students were provided with the integration values listed on the spectrum. The structure and assignments are provided for clarity. Two drops of tetramethylsilane (TMS) were included to mark 0 ppm. The presence of dichloromethane (DCM) indicates residual solvent used during the extraction.

shifts and the splitting patterns that were displayed on the 1H NMR spectrum really helped me tell the difference between the ketone products and, therefore, they allowed me to better identify the starting alcohols that were oxidized to make the product.” Another student recognized the utility of FTIR spectroscopy in this experiment, by stating, “The only feature of the IR spectroscopy [that was] useful was the absence or presence of certain functional groups, but this was only helpful in determining if the reaction went to completion.” The students generally indicated that the products formed were all clear, colorless liquids, recognizing that color was not a helpful indicator for determining the identity of the unknown alcohol. In addition to these rankings, students also self-reported their confidence levels in their ability to identify correctly the unknown alcohol with only the benchtop 1H NMR spectra of their products. Figure 4 illustrates a downward trend in student confidence levels, with most students indicating that they would feel “most confident”. Furthermore, students selfreported their confidence levels in their ability to identify correctly their unknown alcohol without the benchtop 1H NMR spectra of their products. In Figure 5, an upward trend is noted for student confidence levels, with the greatest population of students selecting “not confident”. These data are also included by semester in Supporting Information Figures 12−17. Several concepts taught in the associated lecture course were reinforced with the students through this MOE including the oxidation of alcohols and spectral analyses using 1H NMR and FTIR spectroscopies. Students collected NMR and FTIR spectra of their products that they synthesized from their

assigned unknown secondary alcohols. The presence of a carbonyl absorption in the FTIR spectrum confirmed that oxidation occurred. Students considered the chemical shifts, splitting patterns, and integrations in their 1H NMR spectra along with their products’ molecular formula to elucidate the structure represented in their product spectra. One student described this analysis as follows, “The specific peaks on the spectra were different for each starting alcohol, making it easy to determine which alcohol corresponded to each 1H NMR spectra. The triplet at approximately 1 ppm indicates that the 6 [protons] with that specific splitting pattern are adjacent to a carbon with two [protons]. Those 6 [protons] indicate that the ketone has two methyl groups present on the carbon chain, eliminating 3-methyl-butan-2-ol as a possible starting material, as that alcohol contains 3 CH3 groups. The quartet at approximately 2.25 ppm indicates that 4 [protons] on the molecule have 3 neighbors. This narrows the possible starting material down to 3-pentanol, as the two secondary carbons in this molecule are each adjacent to a carbon with three [protons].” This student’s representative response illustrates that while the students could look at the number of signals in the spectrum to determine their product, other factors were taken into consideration, such as splitting patterns and integration values. The repetition of this type of analysis and structural elucidation of self-made products is an integral component of MOEs. The structure was then matched to one of the three potential secondary alcohol options provided to students. Another student noted the correlation of this experiment with the lecture course, stating the following, “This was an easy introductory lab that actually lined up with D

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Figure 4. Postlab survey responses indicating confidence levels for correctly identifying the unknown secondary alcohol with only the benchtop 1H NMR spectra. The correct and incorrect designations refer to the student identifications of the unknown alcohol. All students in the Spring 2018 iteration identified their assigned unknown alcohol correctly.

While other standard measurements and observations (i.e., product mass and color) were recorded throughout the experiment, the data collected from the postlab survey discussed above clearly show that these spectroscopic analyses, primarily 1H NMR spectroscopy, were key to student identification of the product and the unknown starting material. Additionally, the commentary provided in the student feedback demonstrates an understanding and an appreciation of the utility of the 1H NMR spectroscopy. Overall, MOEs accompanied by benchtop NMR greatly increased student familiarity and confidence with data analysis and their mastery of concepts introduced in the associated lecture.

the material we have been studying in lecture. It’s short and to the point...”. The students who participated in the MOE had a more individualized laboratory experience because they collected and analyzed their own unique data. Their laboratory experience was not uniform across the section or class, unlike the experience in the single-outcome version of the experiment. Student experiences during this MOE individualized once students were assigned an unknown at the beginning of the laboratory period and culminated with the 1H NMR spectra of the resulting ketones, which varied by chemical shift, splitting patterns, integrations, and number of signals. Finally, this MOE actively engaged students with two modern analytical techniques: FTIR and 1H NMR spectroscopies. With TA supervision, students collected spectra of their products and interpreted these data to determine the identity of their products. Many students described their spectral analyses in the postlab survey as previously illustrated. A student noted the following, “Using the 1H NMR data was incredibly useful for aiding in the identification of the product as it provided information on the splitting of the [protons] which helped with figuring out how the [protons] were bonded and how many were bonded to each carbon, and how many different unique bonds there were in the compound.”



CONCLUSIONS MOEs greatly enhance the undergraduate chemistry instructional laboratory experience. Because students obtain individualized experimental results, they assume individual ownership of their data analysis. Indeed, most students enthusiastically engaged in the analysis of the data they themselves had generated. Thus, MOEs allow students in the instructional laboratory to study transformations and chemical processes jointly, but due to individualized results, comparisons and discussions of their results with classmates generate an active learning environment. Moreover, through these comparisons, E

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Figure 5. Postlab survey responses indicating confidence levels for correctly identifying the unknown secondary alcohol without the benchtop 1H NMR spectra. The correct and incorrect designations refer to the student identifications of the unknown alcohol. All students in the Spring 2018 iteration identified their assigned unknown alcohol correctly.

Students more readily associate laboratory experimentation with conceptual development from their associated lecture courses. The researchers are also working toward full student independence on the benchtop 1H NMR instruments as more MOEs are designed and implemented in the UCLCs.

students gain a more thorough understanding of the underlying principles illustrated through the MOE. Benchtop NMR analysis makes data sharing and comparison even more illuminating and instructive. Students gain confidence identifying common experimental results of the transformations and processes studied by all students as well as how to identify the unique aspects of their individualized results. The oxidation of secondary alcohols into ketones represents a highly successful new MOE for undergraduate organic chemistry instructional laboratory courses. Individualized results were obtained readily, and NMR analysis was extremely effective. For all three implementations, 334 of 386 students (87%) correctly identified the unknown secondary alcohol with which they began the experiment. Students selected 1H NMR as the most useful analytical method, with FTIR and color as the second and least useful analytical tools for identifying the unknown alcohol, respectively.



ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available on the ACS Publications website at DOI: 10.1021/acs.jchemed.9b00212. Procedure, table of reagents, student survey, associated spectra, additional representations of data, instructor information for preparing and performing the experiment (PDF, DOCX)





FUTURE DIRECTIONS Several additional MOEs are currently being developed or undergoing initial implementation trials in the UCLCs. Results continue to reaffirm the usefulness and pedagogical improvements associated with individualized experimental results.

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Richard W. Morrison: 0000-0002-2807-6379 F

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Notes

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The authors declare no competing financial interest.



ACKNOWLEDGMENTS This work was classified as “not human research” by the Institutional Review Board at the University of Georgia (STUDY00005731). We express our gratitude to the organic chemistry instructional laboratory staff, TAs, and students for their efforts during the implementations of this experiment.



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