The Three R's of Resource Management in the Undergraduate Organic Chemistry Laboratory Ned H. arti in'" and Frederick S. waldman3 University of North Carolina at Wilmington, 601 S. College Rd., Wilmington, NC 28403 There are many reasons to be concerned about resource management (recycling and waste minimization) in the undergraduate chemistry teaching laboratories. The top two reasons are a desire to minimize unnecessary exposure of students to chemicals and a desire to protect the environment. Important practical considerations include trying to counter the increasing cost of purchasing chemicals and the more rapidly rising expense of properly disposing of chemical waste. Another reason is that resource management affords a n opportunity to teach students by example a sense of responsibility for environmental stewardship. And last, but not least, chemical resource management provides a n excellent way to teach descriptive chemistry, chemical reactions, fundamental chemical princ i ~ l e.sand . nradical auulications of chemistm to students who, too often, see chemistry only in abstract terms. This article describes our efforts a t resource management in the undergraduate organic chemistry laboratory a t the University of North Carolina a t Wilmington, which has a total student enrollment of nearly 8000; about 250 of these students enroll in organic chemistry each year. Our approach to chemical resource management is based on the three R's.
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A.
Reduce the scale of chemical reactions. Recycle produets and reagents, and .Render waste environmentally acceptable for disposal or safer commercial handling. Our system is not simply a n add-on to the traditional set of laboratory experiments. It is a n integral part of each laboratory experiment. Indeed, our approach requires that experiments be planned in sequences and in combination for the greatest benefit. Reducing the Scale Reducing the scale of chemical reactions is currently ~ovularizedbv the microscale a ~ u a r a t u sand laboratorv ie;ts available (1-8).Microscale experiments have advantages over their large-scale counterparts in terms of reduced cost of reagents and waste disposal, but the nonstandard apparatus employed does little to teach standard techniques to future bench chemists who will need to know how to do chemical synthesis on a larger scale with ordinary apparatus. ~ h e i e f o r e we , have opted to follow the middle ground between the traditional macroscale experi-
970
Journal of Chemical Education
ments and newer microscale procedures: milliscale. By this. we mean that most exueriments are uerformed on 0.5-5.0 g of reactant. This scale is small enough to ensure low initial cost of chemicals, reasonable cost of waste disposal, and minimum exposure to chemicals, yet it allows the use of traditional (standard taper) laboratory glassware. We use a 19/22 standard taper organic chemistry laboratory glassware kit that is supplemented by the addition of a 10-mL boiling.flask. Another way in which we reduce the amount of chemicals used and, therefore, also reduce the amount of potential waste generated is by h a v i n ~the students work in pairs or gr&ps of three.- his cooperative learning arrancement has numerous advantages that have been discussed in the recent literature (9,?o),including fostering teamwork skills and reinforcing knowledge by peer-to-peer instruction. Recycling Recycling is done in several ways. The simplest, yet one of the bent methods, is to utilize synthetic sequences (111, in which the product of one experiment is the reactant for the next experiment. Our laboratow manual (121 incorporates threesuch sequences, covering 11three-hour laboratory periods over the two-semester course. Another approach to recycling is using the product of one experiment in a n unrelated subsequent experiment. For example, the D-nitroacetanilide uroduced bv nitration of acetanilide is 'saved for use the following year in a recrystallization exueriment or for identification of a n unknown bv the mixed melting point technique. In some experiments,*the solvent or catalvst can be recovered and used again in another laboratory class doing the same experi&ent. We have reused the concentrated sulfuric acid employed to remove unreacted alcohol from a n alkyl bromide product three times with no detrimental effect. The alumina used in column chromatography of a mixture of substituted anilines is purified by washing with acetone, then dried and reused. E t h y l alcohol u s e d to recrystallize p-ni'A~thorto wnom corresponaence should oe aaaressea. r re sen tea n part at tne 205th National Meeting of the American Chem ca Societv. Denver. CO. Marcn 27-Aoril2. 1993 3~nvironmentai sciencemajor and undergiaduate student chemistry laboratory assistant at UNCW.
troncrtitnilidc may be reused in the same rxprriment without treatment, with the edded advantage that the percent recovery of product actually improve.: after first saturating the solvent with D-nitr~~acetanilide. Lastlc -. we recover reagents or additional product by pooling student samples and evaporating the solvent or allowing a product to crystallize slowly. The mother liquor from the recrystallization ofp-nitroaceta~lidecan be saved and concentrated to provide additional product. This is especially useful in cases of the product isnot important, such as where the in orcoarinr stanine material fbr the student's first introduetion to the techiiques of recrystallization. Obviously, extreme care must be taken to label these recovered, impure chemicals a s such to prevent mistaking them for pure reagents. Rendering the By-products Safe for Disposal Rendering the (minimized) chemical by-products safe for disoosal into the sanitarv sewer svstem or less danwrous for commercial disposal is an excellent opportunity to teach descriptive chemistry, chemical reactions, fundamental chemical principles, and practical applications of chemistry while also fostering environmental responsibilitv. I n manv instances this is a s simple a s neutralizing an aqueous acidic or basic solution, and with careful planning the acidic by-product of one experiment can serve to neutralize the basic by-product of another. Sodium alkoxides are treated with water to convert them to a mixture of the corresponding alcohol and sodium hydroxide, an illustration of relative basicities. Other strategies for pretreating bv-moducts include separating compounds from - oraanic aqueous waste by solvent extraction. where-feasible, we use solvents that have been oreviouslv used (ex.. - . a n ethyl acetate-petroleum ether mixture contaminated with nitroanilines from use in column chromatrography) or prepared by the students (e.g., ethyl acetate) a s the extraction solvents. Aqueous solutions of Cr3+are rendered safer and less costly to dispose ofby precipitation of the chromium a s Cr(OHI3. Silver halide precipitates are collected, added to those collected in other laboratory classes, and sold to a reprocesser. An important aspect of the resource management promam outlined herein is maintenance of a n inventom log of waste to dispose, and proper labeling and storage ofall chemical containers. We employ a n undergraduate student assistant (who is majoring in chemistry or environmental science) to assist a faculty member in the labeling, collection, and inventory logging of all chemical products and by-products. All labels used in the laboratory are produced by a laser printer, making them easy to prepare, UNformly complete, readable, and indelible.
Throughout our plan we have sought to enhance the educational value of the experiment to the student by the inclusion of resource management principles and techniques. Based on verbal feedback and the willingness of the students to participate, the program has succeeded. Summary I n summary, we have developed procedures to manage the chemical resources involved in the undermaduate organic teaching luboratory itt the ilniwrsity o f ~ u r t hCarolina at Wilmington to accomplish the following i h j c ~ ~ i v e i : 1. reduce the amount of chemicals used and. therefore. also
rrdurr the exposure ofstudents ro chrn,icnls.
2. reduce rhe amounr ofcl~em~cal w3Slr gmel-ated. 3. reryclr rhcmtcn. products or rmgerna for use it! uther ex-
periments or for subsequent reuse in the same experiment, 4. render the unusable by-products safer for disposal, 5, incorporate the methodology of resource management into the student's experimental procedure so that students learn strategies and techniques of chemical resource management, and 6. instill in the students a sense of responsibility for environmental stewardship by our example.
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These procedures have resulted in cost savings to the department while providing a n excellent opportunity to teach valuable lessons about chemistry, resource management, and environmental consciousness. Finally, the resource management program has been welcomed warmly by our students, who participated in its development and continue to offer suggestions. Acknowledgment The authors thank the UNCW College of Arts and Seiences for a Faculty Summer Initiative stipend (NHM) and a student laboratory assistantship (FSW) to support this work. Literature Cited 1. Landgrebe, J. A. TheoryandPmdice in the OrgonicLoboroloryuilh Micmsmleand Standard ScoleExperimsnfs, 4th ed.; Bmoks-Cole: Belrnont, CA, 1993. 2. Mayo, D. w.; Pike. R. M.: Butcher, S. S. Micmsmk T#chnipu~srorthe OrgonicLabo~ mtory; John W1ley & Sons: NewYork. 1991. 3. Meyo,D. W.;Pike,R.M.;Butcher, S. S.MicroscoleO?goniclabomlory,2nded.; John Wiley & Sons: New York, 1989. 4. Nirnitz,J.E*pe,imm*s in Organic Chemisf~:FmmMicroacokfoMocmscok;PrentieeHall: Englewood Cliffs, NJ, 1992. 5. Pa~s,D.L.;Lsmprnsn,G.M.;Kriz,G.S.;Engel.R.G.Inlmd~cfiontoOrgonicLobomiory Tpchniqups-Micmscoidppmch;Saunders: Chicago, 1990. 6. Radig. 0. R.: Bell, C. E.: Clark. A K. Organic Chemistry hhomlory:Slondordand Philadelphia, 1990. W c m s c o l ~ E r p ~ m n tSaunders: s;
7. Williamson. K. L. Mueroseai and Micmsrols Oganie Ezpedmnfs: D.C. Heath: Lexingbn, MA, 1989. 8. Wileox, C. F ExperimntolOrgonic Chemilry:ASmoll-SealeApprooeh:Maemillan: Npw Ynrk -~~~ lDRD 9. Mehaffy, P. G.; Newman, K E.; Bestman, H. D. J Chem. Ed-. lWS, 70,7679. 10. Smith. M. E.; Hinck1ey.C. C.;Volk, G.L. J. Chom Educ. 1991. 68.413415. 11. Sayed,Y.:Ahlrnark,C.A.:Mariin,N.H.J. Chrm, Edue 1989.66, 176175. 12. Martin, N H.; Sayed.Y. OrgonicChemislry Lobomtory M ~ n u ~ l w i Woste i h Managem n l and Mokular Mdding, 2nd ed.:Kendall-Hunt: DuBuque, IA, 1993. ~
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