Organic Lab as a Research Experience Multitasking Lisa T. Alty Washington and Lee University, Lexington, VA 24450
A series of articles in this Journal (1-7) has debated the normal versus problem-solving approach to organic chemistry laboratory. Some of the cited advantages of the problem-solving approach include the resemblance to a research experience and that students come to lab more prepared, with an nnderstanding of what will happen in laboratory. This also can be achieved using the normal approach with multitasking, "the concurrent execution of a number of tasks" (8). One way to compel students to understand what is happening in laboratory is to assign more work than can be completed with the casual attitude toward lab that students usually have. I do this by having the students perform more than one experiment a t a time in a given laboratory period. This approach accomplishes similar results to those cited by Pickering (91,when he prohibited the laboratory book from entering the laboratory. In both cases, the laboratory instructor is guaranteed that the experimental procedure has been read in advance of the scheduled laboratory period. Because the student decides individually how to prepare for and execute the experiments, organic laboratory is a more realistic scientific experience. Description The unique quality of this organic laboratory course is evidenced by a glance a t the abbreviated schedule (Table 1).In an obvious departure from the "one period, one experiment" formula, students are carrying out several ex~ e r i m e n tin s each laboratow session. In any one week the student may be asked to start a preparation (designated P and the ex~erimentnumber from the textbook1 and a technique (designated T and the textbook number), or a combination of one or the other. During that same week the student continues experiments started in previous weeks that are to be concluded in that period or in future weeks. A student can complete all of the experiments on time only if t h e student prepares and organizes time wisely. Proper management of time must include spending time before lab reading the experiments, deciding what tasks can be done during dead times (two hour reflux, TLC development, crystal formation, etc.), and setting realistic goals for the four-hour period. Because students make various choices and work a t different rates, individual decisions are made about what will get done in a &+en period. As a result, studentsare not all doingthesame workat the same time and an unprepared student cannot just watch what his or her neighbor is doing and copy it. Part of the prelab preparation also includes gathering data on the properties of the reactants and products of the reaction. Data for a reactant or product includes melting andor boiling points, molecular weight, moles usedproduced, density, refractive index, color, and the compound's solubility in water, ethanol, and dietbyl ether. The student also draws the complete reaction and calculates a thmretical yield of product formed. All ofthis must be approved as correct by the instructor before the student is allowed to proceed with the experiment. Aa a result, students become
well acquainted with sources for this data (I&13) on both organic and inorganic compounds used in the reaction. Table 1. Organic Laboratory Fall Schedule Week Start Continue 2 T16.1 Boiling Point T18,T19 Density, Refractive Index P51 Cyclohexyl bromide 3 P4445 isolation of Eugenol T16.1.TI8, from cloves TI9
Due
. -.
4
P50.2 Methylcyclohexene T14.7,14.8 Gas Chromatography T8 Recrystallization & Melting Point T14.3,14.4Thin Layer
5
(A Grignard rxn)
6
P56.2 & P58.2 Sequence 1: lsoamyl bromide, T14.7.14.8 lsoamyl acetate
P44,45
T16.1,T18,
P44,45
T8 P50.2
P44,45
TB;T14.3,14.4 P60.2 T14.3.14.4 P50.2 P60.2 T14.7,14.8 P56.2& T8 P58.2
7
T10-Group I Vacuum Distillation T20-Group 3 Polarimelry
8
T10-Group 2 Vacuum Distillation T2O-Group 4 Polarlmetry
9
T10-Group3 Vacuum P56.2& Distillation P58.2 T2O-Group 1 Polarimetry P69.2 c/o-Norbornene-5,6end~dicarboxylic Anhydride (a Dieis-Alder rxn) TIO-Group 4 Vacuum P69.2 Distillation T2O-Group 2 Polarimetry P64.1 Methyl 2-nitrobenzoate (Electrophilicaromatic substitution) T27 Elemental analys -
10
11
12
T20-Gr3 P60.2 T14.3.14.4
P56.2& P58.2
-
stands for Preparation,section 3 1m me rex (rr). T16.1 ~tandsforTechnique, senion 16.1 in thetext. Availabilityofequipment P51
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The unprepared student gets behind and loses points in several ways. First, students are not allowed to start the experiment until the data-gathering process mentioned above is complete and correct. Second, if an experiment is turned in late, it is penalized some percentage of that exoeriment's score. Third. the student mav choose to stav for' an extra half hour at the end of the The penal& for staving late increases each successive time the student " stays late to prevent the student from oRen utilizing this opportunity. These penalties may seem slight, but students know that the ultimate result may be the difference between letter grades. Therefore, most students arrive well prepared for laboratory. They quickly become adept at judging what they can and cannot accomplish in a four-hour period, and they learn how to oreanize tasks to attain a eoal. Bv manaeine multiple tasks simultaneously,studentsare mikckinithi habits of oroductive research scientists. This eives students a realistic idea of what practicing laborat& science is like. The other advantage to this type of scheduling is that students do a lot of experiments and, therefore, become accustomed to setting up and executing the routine tasks of a synthetic organic chemist. Table 2 illustrates this point by showing the minimum number of times these tasks are performed in each term. By the second term most students are relaxed, confident, and surprised by how much pride they have in their laboratory accomplishments.
tended and (2) dead time-time in which other thinas could be done easily They also reported yields, constantsfor the final oroducts. and oitfalls not Dointed out bv the text. The threeLstudenk als'commenteh on whether they thought the experiment was easy or hard and why. In desimina - - the schedule for the fall term. I mdtiolied the intensive times by 1.5 to account for my summer students' exoerience versus the naive students' inexoerience. I also divided the dead times by three to estimate the inexperienced students' initial efficiency in using this time. Bv. -iwglina -- the experiments that fit with fall term class topics and that are hecessary for building a technical foundation. I obtained a set of exoeriments for fall term. The experiments were chosen in sequence to fit with the coursework and for maximum overiap of intensive and dead times. Assignment of due dates was accomplished by using the modified times to estimate the expected ffishine date and then addine one week to this date. Amazinelv enough, this shot in the dark worked well the first time through. In designing the schedule for the second term, the intensive times were multiplied by 1.3 and the dead times divided by two. An unexpected problem that was not accounted for the first vear, but that was corrected the second year, was the use of the hoods. More hood time was needed in the second term, and subsequently the experiments had to be rearranged so that enough hood space was available a t the times needed. Otherwise the modified times worked well. Because this method has been in use at our school for years, there is now a lore associated with it. Nonetheless, students are ~ v e an manual to accomDanv the text that explains in derail the schedule, how tocbm&te the prclab infi~nnationsheet. where to find thedata. the oenalties for lateness, the honor system as it applies &laboratory work, safety procedures and disposal, additional hints and precautions for certain experiments, and the grading scheme. The manual, about 12 pages long, answers a lot of questions and eliminates the need for a prelab session every week. The first lab meeting is devoted to the check in of the lab desk with two hours of encouraging comments on how to "survive" organic laboratory.
Methods
Conclusion
I use a published text (14) chosen primarily for its inclusion of seouences of exoeriments in which the student must use k e product ofdne experiment as the starting material for the following experiment. The obvious rationale here is that synthetic organic chemists do this when making new compounds of interest. Another reason for including sequences is to hone a student's technical skill. Technique must be good to obtain a product of high quality and enough yield to continue through one or two more steps. Finallv, because students eet different vields on multiste~ prepaIations, each stud&t must cal&late amounts df starting materials needed and yields for subsequent steps independently of other students. The laboratow stvle described above was in use when I came to the u&ersity. Since the lab had not been updated in over 20 years, I felt there were significant safety and disposal problems that needed to be addressed. I also wanted to use a oublished text rather than a modification of the current in&udor9s manual. With the hope of having a successful first year, I hired three students who had already completed organic chemistry to perform the experiments in the chosen text during a summer. The students kept track of the time it took them to do the experiment in two ways: (1)intensive time -time in which no other task could be performed or closely at-
The self-confidence established in this laboratory extends to other situations that the student encounters later. Many students are no longer intimidated by upper level science courses with laboratories and some actually feel that a course with a lab will eive them an advantaee. In addition, a striking number of our chemistry majors choose to do scientific research in the summers. Seventy-three percent of our rising seniors over the past three years participated in summer research programs here and elsewhere. Onlv - 18 ~ercentof these students are future chemists. There are several ways to mimic a research experience in the soohomore organic laboratow. Previous articles in this ~ournbl(l-5)foc&ed on the piblem-solving approach to match the thought process of the research organic chemist in the laboratory. Instead, this approach matches the organizational prdcess of a researchlaboratory scientist by usine multitaskine. The students must decide the order and time needed to carry out experiments and how to overlap nonproductive times in one experiment with productive gains in other experiments. The skills students develop-in both technique and time management serve them well in later scientific research laboratorv ex~eriencesand in their professional lives.
Table 2. Technique Repetition
Minimum Number of Times Performed
Technique Distillation Filtration Recrystallization Boiling Point Melting Point Extraction
First 12 weeks
Second 12 weeks
13
8
10 4
19
7
3
6
18
17
9
7
-
664
Journal of Chemical Education
-
-
- .
Acknowledgment
I am indebted to the late J. Keith Shillington whose idea I adopted and revitalized for the organic laboratory. I also acknowledge the help of three students, David Cassada, Matt and Mike Stanchina, who spent a summer doing the current experiments so that I could know the Finally, I gratetirne needed to completeeach fully acknowledge George S. Whitney and Dusan Janjic whose help and patience made this lab approach a success. Literature Cited 1. Venkatachelam, C.: Ruda1ph.R. W. J C h . Ed-
lV74,52. 419482.
2. fickerng, M. J. them. E ~ Z 1986,62,874-875. . 3. Piekering, M. J. Cham. Edue. 1988.65.143-144, 4. Piekering, M. J. Chem. Edue. 1991.68.232234. 6,Cooley,J. H. Cham,Edvc lBB1, 68, 503504. 6. ande el,^. J. c h .E ~ U C1989,66,322323. 7. &an, R rl them. E ~ W1988,66,3n-3~4. . 8. Dielioury o f C o m p ~ t2nd ~ . ed.: Illingwolth. y,Ed.; (hdord Univmity: Word, 1986. ~ 2 4 6 . 9. ~ i c k e r i n g ,J. ~ C. O I I sci. m ~ l m ,.z s , n a ~ ? . 10- T h e M w k I n d w 10th 4.;Wmdhala, M.. Ed.: Merek:Rahway, NJ, 1963. 11. CRC H o d b o d ofChpmistry a d Physics, 65th ed.; Weast. R. C., Ed.; CRC: B a a to". FL, 1984. 12. DietionaryofOrs.nkCompounds,6thed.;~uehingham. ~.,~d.;cha~manand~dt New York, 1982. 13. Long~'8H o d b m k of Chemistry, lm 4.;Lanp, N. A,. Ed.; MeDraw-HOI: New york,1967. 14. Ault,A. lhchniguesondEzpsps~nBforOrgonk Chemistry, 6thed.;AUyn &Barn": Boaton, 1987.
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