Convenient Synthesis of a Lactone, ?-ButyrolactoneRichard E. Bozak, J. Knittel, and Ronald J. HicksJournal of Chemical Education 75(1), 84 (1998)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.
ProcedurePlace 1.5 g (11.9 mmol) of ?-hydroxybutyric acid sodium salt
4 into a 5-mL conical vial that contains a spin vane. Carefully add 1.5 mL of 9 M H
2SO
4, 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
2Cl
2. 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 second 1.5 mL portion of CH
2Cl
2 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 Na
2SO
4 (at least 15 minutes).
Transfer the dried CH
2Cl
2/lactone extract, using a clean filter-tip pipet, to a pre-weighed vial. Evaporate the CH
2Cl
2 using a hot-plate and a gentle stream of N
2 until the weight of the vial and liquid remains constant, then re-weigh. Determine the percent yield in the usual manner, obtain an IR spectrum, and compare it to an authentic IR spectrum of ?-butyrolactone.
Literature Cited1. 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. 3, 433-452 (1964)
(
https://www.thevespiary.org/rhodium/Rhodium/pdf/ghb.review.laborit.pdf)