In the Laboratory The Microscale Laboratory
Convenient Synthesis of a Lactone, γ-Butyrolactone Richard E. Bozak, J. Knittel, and Ronald J. Hicks Department of Chemistry, California State University, Hayward, Hayward, CA 94542 Lactones are cyclic esters. They are claimed to be most stable when the ring is either 5- or 6-membered (1). While lactones are usually ignored in first-year organic chemistry, this experiment shows that they might have some pedagogical virtues. The starting material in this student-oriented microscale experiment is a commercially available salt (2). Also, the boiling point is noteworthy in that the open-chain form, ethyl acetate, has a boiling point of 77 °C, whereas the ring form boils at 206 °C! One might ideally end this experiment with a vacuum distillation (3). In our hands, the KBr pellet IR spectrum had its C=O stretch at 1763 cm{1. Procedure Place 1.5 g (11.9 mmol) of γ-hydroxybutyric acid sodium salt (4) into a 5-mL conical vial that contains a spin vane. Carefully add 1.5 mL of 9 M H2 SO4, attach an air condenser, and reflux the mixture for 15 minutes. Upon cooling, crystals of sodium sulfate may form. Extract the reaction mixture with 1.5 mL of CH 2Cl2. Shake well with frequent venting. Allow the phases to separate and transfer the upper layer, using a filter-tip pipet, to a glass centrifuge tube. Repeat the extraction with a
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second 1.5 mL portion of CH 2Cl2 and transfer the upper layer to the centrifuge tube as before. Dry the organic phase in the corked centrifuge tube with three microscoopula tips (about 0.25 g) of anhydrous Na2 SO4 (at least 15 minutes). Transfer the dried CH2Cl2/lactone extract, using a clean filter-tip pipet, to a preweighed vial. Evaporate the CH2 Cl2 using a hot-plate and a gentle stream of N2 until the weight of the vial and liquid remains constant, then reweigh. Determine the percent yield in the usual manner, obtain an IR spectrum, and compare it to an authentic IR spectrum of γ-butyrolactone. Literature Cited 1. Roberts, J. D.; Caserio, M. C. Basic Principles of Organic Chemistry; Benjamin: Menlo Park, CA, 1964; p 529. 2. Catalog Handbook of Fine Chemicals; Aldrich Chemical Company: Milwaukee, WI, 1996–1997; p 813. 3. See, for example: Pavia, D. L.; Lampman, G. M.; Kriz, G. S.; Engel, R. G. Organic Laboratory Techniques, A Microscale Approach; Saunders College: Orlando, FL, 1995; pp 677–693. 4. In biology-oriented areas, this is referred to as “GHB”; see, for instance, Laborit, H. Int. J. Neuropharmacol. 1964, 3, 433.
Journal of Chemical Education • Vol. 75 No. 1 January 1998 • JChemEd.chem.wisc.edu
