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The Effect of the Nucleophile/Electrophile Reaction Guide on the Performance of Undergraduate Organic Chemistry Students

Donna J. Nelson
Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK  73019

Introduction
    Organic chemistry is often described as a difficult discipline because there is such a large amount of information to be learned.  There is a need to visualize organic reaction pathways and become familiar with the key steps in many reaction mechanisms.  Many of these are reactions between one nucleophile from a group of nucleophiles and one electrophile from a group of electrophiles.  In order to facilitate pattern recognition and learning various nucleophiles, electrophiles, and their reaction mechanisms, we developed a device consisting of a pair of working permutation lists for the reactions of representative nucleophiles with electrophiles typically covered in the undergraduate Organic Chemistry I and II courses.  The device was designed to facilitate recognition of patterns in the reactions of nucleophiles with electrophiles in organic chemistry.  Since the device assists students in visualizing mechanisms of reactions between nucleophiles and electrophiles, it was named the Nucleophile / Electrophile Reaction Guide.
    The Nucleophile / Electrophile Reaction Guide [1-5] contains a page of nucleophiles and a page of electrophiles, grouped according to similarities.  The two pages are juxtaposed (Figure 1) in order to visualize the mechanisms of reactions of nucleophiles and electrophiles common to organic chemistry and to facilitate remembering and differentiating (1) the nucleophiles and electrophiles, (2) the active site(s) in each, and (3) the arrow(s) designating the flow of electrons in the reaction of the two.  An additional result of aligning the pages of nucleophiles and electrophiles in order to visualize reactions, was identification of potential reactions not covered in the classroom or found in an undergraduate organic chemistry text.  However, many of these can be found in the literature.
    An effort to summarize as briefly as possible was a major goal in the design of the device.  Because there is only room for a few structures on each page, entire classes of compounds often are represented by one structure.  For example, all alkyl halides are represented simply by R-Hal, and all alcohols are represented by R-OH.
    Although student responses were quite favorable during the development and first introduction of the device (List 1), it seemed of interest to determine quantitatively the effect of using the device on student performance.  Accordingly, we have investigated the effect of the use of the Nucleophile / Electrophile Reaction Guide on the test performance of students enrolled in undergraduate organic chemistry.

I.   Measuring Effect of the Nucleophile/Electrophile Reaction Guide
A.  Method
    The subject samples were  enrolled in a first-semester organic chemistry course for science and engineering majors at a comprehensive public university.  The sample consisted of 126 students; 63 were assigned to a control group, 17 were assigned to out-of-class device group, 25 were assigned to in-class device group, and 21 were assigned to use the device both in class and out of class (Table 1).  Assignments were random, and the course met for a total of 150 minutes per week for the 15-week semester.  There were four different groups organized according to device use.  Group YY saw demonstrations of how to use the device in class, mimicked the use of the device in class, and then used it unsupervised outside class.  Each student in an in class device group (Group YN) saw the demonstration, mimicked the demonstration with a device, continued to use the device in class, but did not use the device outside class.  Each student in the out of class device group (Group NY) saw demonstrations of how to use the device in class and then used the device unsupervised outside class.   The students in the control group (Group NN) did not use the Guide at all.   Thus, the uses of the device by Group YY would be a combination of those of the in class group (Group YN) and of the out of class group (Group NY) described above.
    The experimental design is a posttest-only control group design for both content knowledge and problem solving.  The questions used in the posttest are given in Table 2.  A Control Unit Achievement Test (CUAT) [6] showed that the groups were approximately equivalent in their chemical knowledge before the treatment.

B.  Results and Discussion
    The results from the Nucleophile / Electrophile Reaction Guide study are shown in Table 1, and the test questions are in Table 2.  These questions were designed to determine student knowledge of various aspects of nucleophiles, electrophiles, and reactions and/or mechanisms involving nucleophiles and electrophiles.  The percent correct response for each test question is shown for each of the sample groups, Group YY, YN, NY, and NN (columns 1-3 and 5), as well as for a weighted average of all groups using the device in any manner (column 4).
    The Control Unit Achievement Test (CUAT) scores for the groups indicate that there was no difference between the three treatment groups and the control group:  YY, 66.1%; YN, 69.8%; NY, 62.8%; NN, 66.8%.  The weighted average for all groups using the device is 66.4%, almost identical to that of the control group.  Grade Point Averages (GPAís) of the students were collected from student records, and averages of these for the groups are also given in Table 1.  However, the GPAís of the groups of students are so similar that no conclusions can be drawn from this information.
    The average of the five questions for each group is given in Table 1 (Ave Q1-Q5).  The results are as follows:  Group YY, 70.5%; Group YN, 73.6%, Group NY, 73.0%, Group NN, 64.1%.  All three of the groups which used the Reaction Guide (Groups YY, YN, and NY) performed significantly better than those of the control group (Group NN), and the weighted average of all groups using the device is 72.4%.  Curiously, of the three groups using the device, the group which used the device both in and out of class scored marginally lower than the other two.  The control group had the lowest average score on every test question except one (Question 3), and in that one it had the next to lowest score.
    If the average results (Ave Q1-Q5) are normalized using factors obtained from the CUAT scores (control score - group score), the corrected averages (corrected average Q1-Q5) become Group YY, 71.2%; Group YN, 70.6%, Group NY, 77.0%, Group NN, 64.1%.  This analysis of the results shows that Group NY shows improvement which was greater by 10.1% (compared to YN) to 20.1% (compared to the control NN) as a result of using the Reaction Guide.  However, use of the device outside of class in addition to using it in class gives only a small improvement, as learned by comparing groups YY (71.2%) versus YN (70.6%).
    The result that Group NY shows the most improvement is somewhat curious, since this indicates that using the device only outside of class is superior to using the device both inside and outside of class.  There seemed at least two possible reasons for this:  (1) the students using the guide only out of class must put more thought into determining how to use the guide and thereby learn more from the effort invested and (2) the students using the guide in class are distracted from the lecture and therefore learn less during it.  In order to obtain additional information regarding the reason for this result, the members of Group NY were subsequently given a questionnaire containing the following: 
 
1.  Why did you use the device only outside of class and not during the class period also?
2.  Approximately how many hours per week did you use the device?
3.  Were these hours evenly spread out through the week or all in one sitting?
4.  Did you use the device with other students or by yourself?
5.  Did you recall how to use the device from seeing it demonstrated in class or did you
     have to figure out how to use it yourself from the instructions on the device?
6.  Please give any other information regarding your use of the device.
 
    Answers to most of the questions revealed no pattern.  For example, about half the students studied alone, and half studied with one or more friends.  About half the students remembered how to use the device from class, and half deduced how to use it themselves outside of class.  There was no pattern to the periods of use of the device.  However, most of the students using the device only outside of class stated that they did not use the device in class because it distracted them from the lecture.  These comments combined with the results of the study indicate that the recommended method of use of this device should be as an out-of-class supplement.

Conclusion
    The design group had significantly higher scores than the control group on the posttest.  The control group had the lowest average score on every test question except one, and in that one it had the next to lowest score.  This indicates that the Nucleophile / Electrophile Reaction Guide improved student performance in this undergraduate Organic Chemistry class.  Data from the performance of the design groups and information from a subsequent questionnaire indicates that the best method of use of this device for most students is probably as an out-of-class supplement.

Acknowledgment
    We are grateful to Lucent Technologies and Sunwest Capital Corporation for support of this work.

References
1.  Nelson, Donna J.  Proc. 40th ACS Oklahoma Pentasectional Mtg., Norman, OK, April 29, 1995.  American Chemical Society, Washington, DC 1995, Paper No. 40.
2.  Nelson, Donna J.  Nucleophile / Electrophile Reaction Guide for Organic Chemistry;  Jones and Bartlett:  Sudbury, MA, 1997.
3.  Nelson, Donna J.  Proc. 215th ACS Natl. Mtg., Dallas, TX, March 29, 1998. American Chemical Society, Washington, DC 1998, ORGN 126.
4.  (a)Stills, S. (ed.)  Chemical & Engineering News 1998, April 13, p. 47. (b)Gillham, O.  The Norman Transcript, May 5, 1998, p. 1A.
5.  "Teaching Devices to Make Undergraduate Organic Chemistry Easier."  Nelson, Donna J.    Proceedings of the 26th National Triennial Convention of Iota Sigma Pi; Iota Sigma Pi Promethium Chapter:  Portland, OR, 1999.
6. Aldamash, A. "Kinetic Versus Static Computer-Generated Visuals for Facilitating College Students Understanding of Reaction Mechanisms in Organic Chemistry," Ph. D. Dissertation.  University of Oklahoma, Norman, OK,
1995, pp 42-44.  Before the treatment, students' knowledge in chemistry was tested over a unit of instruction with no content which served as the treatment for the research.  Corrections were based on differences in results of the groups of this control unit achievement test (CUAT).

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