Research: Science and Education
Spectroscopic Instruction in Introductory Organic Chemistry: Results of a National Survey Christopher W. Alexander, Gary L. Asleson, Marion T. Doig, and Frederick J. Heldrich* Department of Chemistry & Biochemistry, College of Charleston, Charleston, SC 29424-0001; *
[email protected] Spectroscopic analysis is an integral and increasingly important part of the introductory organic chemistry curriculum. The current guidelines for the organic chemistry curriculum updated in 1997 by the Committee on Professional Training of the American Chemical Society list 1H NMR, 13C NMR, UV–vis, IR, and MS as topics to be covered in lecture. The same CPT guidelines recommend hands-on use of UV–vis, IR, NMR, and MS for the organic laboratory curriculum. While it is not mandated that these items be covered in the introductory organic chemistry curriculum, it is reasonable to assume that they are covered in many introductory courses nationwide. There is an apparent expectation by ACS that this is in fact occurring in a majority of ACS-certified departments. That expectation is confirmed by the 1998 ACS standardized examination1 for the year-long course in introductory organic chemistry, which includes 5 of 70 questions covering IR, 1H NMR (PMR), 13C NMR (CMR), and MS. In comparison, there are 2 questions on IUPAC nomenclature, 3 questions directly related to configuration, and 5 questions about electrophilic aromatic substitution chemistry on the examination. Further evidence that spectroscopic analysis has become a central part of the introductory organic curriculum is found by examination of the content of recent commercial lecture and laboratory textbooks designed for the course. As seen in Tables 1 and 2, both laboratory and lecture texts devote considerable space to spectroscopic analysis of organic molecules.
Survey Rationale To determine how instructors of the traditional introductory organic chemistry courses are handling spectroscopic instruction, we sent a questionnaire to all chemistry departments offering ACS-certified degrees. For the 617 distributed surveys there were 321 respondents, or a 52% return. Our objective was to answer three fundamental questions. First, which spectroscopic techniques are covered in the introductory organic course? Second, what style of teaching is used for spectroscopic analysis instruction? And finally, where (i.e., lecture or laboratory) are students expected to learn about spectroscopic analysis? Given the contents of current texts, it seemed reasonable to expect spectroscopic instruction would be common in both lecture and laboratory settings. It also seemed likely that most schools would cover IR, PMR, and CMR, since they appear in almost all of the available texts. It is noteworthy that while instructors might prefer to cover CMR before PMR, the texts generally present PMR first. We anticipated that MS instruction would be less common, largely owing to the fact that affordable bench-top GC–MS instruments have only recently been routinely available and because MS is not covered in many laboratory texts. With regard to teaching style, we anticipated that the lecture-by-technique approach would preTable 2. Spectroscopic Coverage in Some Organic Chemistr y Laborator y Texts and Manuals Text/Manual
Table 1. Spectroscopic Coverage in Some Organic Chemistr y Lecture Texts
1 of 22
IR, PMR, CMR
Bell et al. Organic Chemistr y Laborator y 2nd ed., 1997, Saunders
3 of 48
IR, CMR, PMR, MS
Svoronos et al. Organic Chemistr y Laborator y Manual 2nd ed., 1997, Wm. C. Brown
1 of 24
IR, PMR, UV–vis
3 of 38
IR, PMR, CMR
Topics Covered (In Sequence)
Bruice, 2nd ed. 1998, Prentice-Hall
2 of 28
MS, IR, PMR, CMR, COSY, HETCOR, UV–vis
Brown & Foote, 2nd ed. 1998, Saunders
3 of 28
MS, PMR, CMR, IR, UV–vis
Fox & Whitesell, 2nd ed. 1997, Jones & Bartlett
1 of 23
PMR, CMR, IR, UV–vis, MS
Jones 1997, W. W. Norton
1 of 26
Moore & Winston Laborator y Manual for Organic Chemistr y 1996, McGraw-Hill
MS, IR, PMR, CMR
Cary, 3rd ed. 1996, McGraw-Hill
1 of 27
PMR, CMR, IR, UV–vis, MS
Pavia et al. Organic Laborator y Techniques 2nd ed., 1995, Saunders
McMurry, 4th ed. 1996, Brooks/Cole
3 of 31
MS, IR, PMR, CMR, UV–vis
Solomons, 6th ed. 1996, Wiley
1 of 25 (& 2 of 15 "special topics")
UV-VIS, IR, PMR, CMR, COSY, HETCOR, MS
Loudon, 3rd ed. 1995, Benjamin/Cummings
3 of 27
IR, MS, PMR, CMR, UV–vis
Vollhardt & Schore, 2nd ed. 1994, Freeman
4 of 26
PMR, CMR, IR, UV–vis, MS
1294
Topics Covered (In Sequence)
Gilbert & Martin Experimental Organic Chemistr y 2nd ed., 1998, Saunders
SpectroscopyOriented Chapters
Text
Spectroscopy Chapters
Zanger & McKee Small Scale Syntheses 1995, Wm. C. Brown Williamson Macroscale and Microscale Organic Experiments 2nd ed., 1994, D.C. Heath Campbell & Ali Organic Chemistr y Experiments 1994, Brooks/Cole
≈ 3 of 85 IR, PMR, CMR (3 appendixes) 1 of 22
IR, PMR, CMR
3 of 71
IR, PMR, CMR, UV–vis
1 of 17
IR, PMR
Journal of Chemical Education • Vol. 76 No. 9 September 1999 • JChemEd.chem.wisc.edu
Research: Science and Education
dominate because the material is largely organized in that manner in texts. Results
Techniques Covered The data indicating which techniques are being taught are shown in Table 3. To determine the spectroscopic techniques being covered we simply summed the numbers of courses that included any amount of instruction in the lecture or the laboratory. IR, PMR, and CMR were the most commonly taught techniques in lecture. The techniques that are being taught in the laboratory seem predictably related to two factors, namely, cost of the instrumentation and general utility of the technique. For example, nearly everyone includes IR as part of the laboratory curriculum, undoubtedly because IR instruments are relatively inexpensive and easy to use and the spectra are readily interpreted. On the other hand, the relative dearth of laboratory UV–vis and MS instruction is probably due to different factors. UV–vis, where instrumentation is relatively inexpensive, may suffer from the perception that not enough information is obtained to warrant time spent preparing the sample or running the instrument. Most lecture texts include UV–vis with the topic of conjugation, and so it is not surprising that many courses include UV–vis in the lecture, even if the information derived from the spectra is perceived to be of limited general value. For MS, the information content for many common organic compounds is relatively rich and sampling by means of hyphenated GC–MS systems is easy, but the cost of instrumentation can be prohibitive. The use of new PDA detectors associated with HPLC may have an impact on UV–vis utilization similar to the impact that the GC–MS has had for MS (1). Most laboratory texts do not include UV–vis or MS, so their presence in the laboratory curriculum is probably the result of special efforts made by some instructors. CMR has only recently been available to most undergraduate laboratories, and the newer high-field FT instruments are more expensive to purchase and maintain than the CW instruments that they replace. This may explain why PMR instruction is about double that of CMR in the laboratory. Very few schools introduce 2-D NMR techniques in the organic course. Only 12 teach 2-D in both lecture and laboratory, 24 teach it just in lecture, 8 teach it just in the laboratory. One might expect that as FT–NMR becomes routinely available to undergraduate laboratories, then 2-D NMR will become more common. Incredible structural information is Table 3. Spectroscopic Instruction in Lecture and Laborator y Taught in (% of Respondents) Technique Lecture Laboratory Lecture or Lab Lecture and Lab IR
89.7
92.8
98.8
83.8
PMR
91.6
86.0
98.1
79.4
CMR
80.4
45.2
86.6
38.9
MS
69.5
38.0
76.0
31.5
UV–vis
61.4
32.1
66.7
26.8
2-D
11.2
6.2
13.7
3.7
1.9
0. 6
1.9
0. 6
Othera a”Other”
spectroscopy techniques include X-ray, ESR, CD, and ORD.
afforded by 2-D experiments such as COSY or HETCOR, whose spectra can often be interpreted as easily as any standard X–Y plot (2). In broad terms, the data of Table 3 can be used by instructors tasked with the design of the organic course to differentiate among the techniques that might be considered for inclusion in the curriculum. From a practical standpoint, the entirety of the course curriculum needs to be addressed for this purpose. Those techniques that are taught in either the lecture or the laboratory portion of the course by over 75% of the respondents (IR, PMR, CMR, MS) might reasonably be classified as core techniques of the introductory organic course. While not manifest in Table 3, 276 respondents (86%) teach PMR, CMR, and IR. However, only 222 (69%) include all the core techniques (PMR, CMR, IR, and MS) in their curriculum. IR and PMR appear to be mandatory parts of the organic curriculum, as both are taught by all but 4 respondents. UV–vis, while arguably not part of the core, is very nearly essential and clearly desirable, being part of the course for two-thirds of the survey respondents. Other techniques, including 2-D NMR, are included in a minority of courses and must be considered currently to be nonessential to the core. Only 3 respondents reported that no spectroscopy was included in their curriculum. These classifications are dynamic and will undoubtedly change rapidly as instrument technologies and spectroscopic techniques advance. Apparently, those who want to be at the forefront of curricular design should include PMR, CMR, IR, MS, and UV–vis and might strongly consider 2-D NMR.
Teaching Style Table 4 presents a summary of the data gathered concerning how spectroscopy is being taught in the introductory organic curriculum. To facilitate the data analysis, we set forth what we felt were the most likely scenarios in which spectroscopy might be presented to the students. We asked respondents to indicate the style most representative of their approach. In the 14 instances where two styles were reported, we counted both styles, assuming they were used equally. This resulted in a total of 325 teaching style responses for the lecture and 315 styles for the laboratory. It is not unreasonable to find that the predominant style Table 4. Teaching Methods Used in Lecture and Laboratory Settings Method Description
% Using Method Example
Lecture
Lab
70.8
23.5
Lecture, spectral characterization of alkanes
9.8
7.0
C Assignment on each technique with minimal or no lecture support
Assigned reading followed by application
0.9
16.8
D Assignment using multiple techniques with minimal or no lecture support
Characterization of compound by IR, NMR, and MS
1.2
24.4
E Assignments on focused aspects of a technique, gradually building to comprehensive characterization
Assigned reading (use of [M]+/[M +1]+ ratio in M S), building to characterization by IR, NMR, and MS
11.4
22.2
F Material not covered
—
5.8
6.0
A Lecture format, organized by technique
Lectures on IR, 1 H NMR, etc.
B Lecture format, organized by functional group
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of presentation in lecture is lecture by technique (style A). This conforms to the most common style of presentation in currently available lecture and laboratory texts. Style E (focused assignments) was more popular than style B (lecture by functional group) in lecture. Apparently quite a few instructors rely heavily on textual material and independent student learning, as opposed to didactic lecture, to cover spectroscopy. The striking diversity with which spectroscopy is presented to students in the laboratory environment is noteworthy. There is much reliance on student self-study, as indicated by style C (assignments on techniques), style D (assignments using multiple techniques), and style E. Quite a few courses favor the use of lectures in the laboratory (styles A and B). Style E, which is not a style one would readily anticipate by looking at presentations in current texts, was surprisingly popular in both lecture and laboratory settings (3).
Lecture–Lab Allocation Table 5 summarizes the data from the 196 respondents who indicated the apportioned teaching effort for lecture and laboratory instruction for each technique. In fact, the general trend for apportionment of effort between laboratory and lecture with regard to instruction for the five most common techniques (UV–vis, IR, MS, PMR, and CMR) favors lecture over laboratory by a factor of 2:1. It is not surprising that only in the case of IR is the apportioned instructional effort in the laboratory equal to or greater than that which occurs in the lecture. Even if all instrumentation needed for an organic laboratory were to be purchased anew, the FTIR would still be one of the most cost-effective instruments that could be acquired. Perhaps, if a snapshot of apportioned effort is made in 25 years after more instruments have been added to the arsenal for instructional laboratories, then a greater percentage of the instructional effort for core techniques will be taking place in the laboratory curriculum. It was pointed out by a reviewer that in a recent article Steehler reported his impression that faculty do not strongly support the use of instrumentation in introductory courses (4 ). The results of our survey seem to indicate otherwise. Of the five topics (PMR, CMR, IR, MS, and UV–vis), 95% teach at least one, 90% teach at least two, 64% teach at least three, 37% teach at least four, and a robust 13% teach all five in the laboratory portion of the course. Additionally, approximately a third of the apportioned spectroscopic instruction occurs in the laboratory (Table 5). Finally, less than a third teach by lecture in the laboratory (Table 4). Since a substantial portion of instruction occurs experientially in the laboratory, it seems highly probable that there is strong support for and practice of student hands-on use of instrumentation in introductory organic chemistry. To confirm this conclusion, we sent out a smaller survey to a subset of the ACS certified departments to address that specific issue.2 The results allay the fears raised by Steehler and confirm the conclusion drawn from the initial survey data. By a large majority (89%), faculty gave an affirmative response to the question: “In general, do you feel that student hands-on use of instrumentation in introductory organic chemistry is appropriate?” With regard to the current practice of hands-on use in introductory organic laboratory courses, those surveyed reported that 96% use IR, 55% use PMR,
1296
Table 5. Division of Teaching Time between Lecture and Laborator y % of Teaching Time a
Technique
Lecture
Laboratory
IR
46.9
53.1
PMR
58.0
42.0
CMR
69.8
30.2
MS
69.0
31.0
UV–vis
72.2
27.8
Average 2-D NMR Other
b
67.5
32.5
56.3
43.7
100
0.0
aData
are from 196 respondents. percentage of effort, apportioned between lecture and laboratory, for IR, PMR, CMR, MS, and UV–vis. bAverage
43% use GC–MS, 39% use UV–vis, 34% use CMR, and only 9% use 2-D NMR. Conclusion Unquestionably, spectroscopy has become a core part of the introductory organic course. Significantly, it is more likely to be incorporated into the laboratory curriculum when students are able to have hands-on exposure to instruments. The variation and amount of instruction (particularly in the laboratory) may be driven, in part, by the efforts of the National Science Foundation Division of Undergraduate Education Instrumentation Laboratory Improvement program, which has stressed, as one of its funding criteria, innovation in the use of instrumentation in the laboratory curriculum. Notes 1. Similar coverage was provided for the 1994 examination. ACS DivCHED Examinations Institute, Clemson University, Clemson, South Carolina. 2. The supplemental survey was sent to 97 individuals representing a sampling of small, medium, and large departments in public and private institutions awarding a variety of degrees (B.S., M.S., Ph.D.). Forty-four of those surveyed responded.
Literature Cited 1. Asleson, G. L.; Doig, M. T.; Heldrich, F. J. J. Chem. Educ. 1993, 70, A290–A294. 2. Duddeck, H.; Dietrich, W. Structure Elucidation by Modern NMR. A Workbook, 2nd ed.; Springer: New York, 1992. 3. Alexander, C. W.; Asleson, G. L.; Beam, C. F.; Doig, M. T.; Heldrich, F. J.; Studer-Martinez, S. J. Chem. Educ. 1999, 76, 1297–1298. 4. Steehler, J. K. J. Chem. Educ. 1998, 75, 274–275.
Journal of Chemical Education • Vol. 76 No. 9 September 1999 • JChemEd.chem.wisc.edu
