Introduction: (Note: the first two paragraphs in this section were directly taken from Wikipedia:

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1 Exp t 125 Camphor from Isoborneol: An Oxidation Adapted by and R. Minard (Penn State Univ.) from Introduction to Organic Laboratory Techniques: A Microscale Approach, Pavia, Lampman, Kriz & Engel, Revised by John Landis, Rev. 3/21/01 Introduction: (Note: the first two paragraphs in this section were directly taken from Wikipedia: Camphor is a white transparent waxy crystalline solid with a strong penetrating pungent aromatic odor. It is a terpenoid with the chemical formula C10H16O. It is found in wood of the camphor laurel (Cinnamonum camphora), a large evergreen tree found in Asia (particularly in Borneo, hence its alternate name) and some other related trees in the laurel family, notably Ocotea usambarensis; it can also be synthetically produced from oil of turpentine. It is used for its scent, as an embalming fluid and for medicinal purposes. Modern uses include as a plasticizer for cellulose nitrate, as a moth repellent, as an antimicrobial substance, in embalming, and in fireworks. A form of anti-itch gel currently on the market uses camphor as its active ingredient. It is also used in medicine. Camphor is readily absorbed through the skin and produces a feeling of cooling similar to that of menthol and acts as slight local anesthetic and antimicrobial substance. It may also be administered orally in small quantities (50 mg) for minor heart symptoms and fatigue. Camphor is also used as a flavoring in sweets in India and Europe. It is thought that camphor was used as a flavouring in confections resembling ice cream in China during the Tang dynasty (A.D ). In larger quantities, it is poisonous when ingested and can cause seizures, confusion, irritability, and neuromuscular hyperactivity. In 1980, the United States Food and Drug Administration set a limit of 11% allowable camphor in consumer products and totally banned products labeled as camphorated oil, camphor oil, camphor liniment, and camphorated liniment (but camphor is absent in "white camphor essential oil"). Since alternative treatments exist, medicinal use of camphor is discouraged by the FDA, except for skin-related uses, such as medicated powders, which contain only small amounts of camphor. This experiment involves the oxidation of a secondary alcohol (borneol) to a ketone (camphor) as illustrated in the first step of the two-step oxidation/reduction sequence shown below. The use of a polymer-supported chromic acid used for the oxidation makes isolation of the product very simple. It is simply removed from the resin by pipet filtration. Oxidation Reduction Borneol H OH Resinsupported CrO 3 Camphor O NaBH 4 Isoborneol H OH The spectra of borneol, camphor, and isoborneol are compared to detect structural differences and to determine the extent to which the final step produces a pure alcohol isomeric with the starting material. Prelaboratory Exercises: 1. Annotate the reference IR spectrum of camphor at the end of this handout.

2 2. What do the terms exo and endo mean? Give an example of each. Cautions: The reaction should be carried out in a hood. The resin-supported chromic acid oxidizing agent is toxic. Avoid contact with skin and dispose of as a heavy metal. The starting material and product sublime readily and should be stored in tightly closed containers such as "shorty" vials. Synthesis: To a 5-mL long-neck round-bottom flask, add g of [(1s)-endo]-(-)-borneol, 2.0 ml of toluene, and 0.50 g of chromic acid on a polymer support resin. Clamp the flask on the surface of a hot sand bath and heat so that the toluene just boils gently (bp 110 C). TLC You are required to run a TLC to monitor the progress of the reaction. Plates should have three spots (or lanes) on the origin: one for the main organic starting material that is being transformed (i.e. 2% solution of borneol), one for a cospot (starting material and the reaction mixture), and one for the reaction mixture. At intervals of 5 min, insert a long finely-drawn capillary into the reaction to draw liquid into the capillary and spot on a silica gel TLC plate (available from the stockroom). Develop the TLC plate in 50% hexane/50% ethyl acetate and visualize using an iodine development chamber. The reaction should be complete in approx. 30 min. Isolation and Purification: Allow the mixture to cool to room temperature and draw off the toluene by pipet filtration and place it in a tared 20-mL vial. Add a boiling stick and evaporate the solvent in the hood by heating the vial on a warm sand bath. If possible, use a gentle stream of nitrogen gas to aid the evaporation. Watch the progress of the evaporation carefully and, as soon as a solid appears, remove the vial from the heat source; otherwise, the product may sublime and be lost. Lay the warm vial on its side on the bench top and roll around to allow the heavy toluene vapors to escape. Weigh the vial and oily solid to determine the weight of your product and calculate the percent yield. Cap the vial since the product sublimes readily. Determine its melting point in a capillary tube sealed with Parafilm to prevent sublimation. The melting point of pure racemic camphor is 174 C 1. However, the observed m.p. of camphor is often low. A small amount of impurity drastically reduces the melting point and increases the mp range. Cleaning Up: The used chromic acid resin should be placed in the heavy metals waste container. Analysis In addition to TLC analysis, you may be instructed to analyze your final product by IR, GC or GC- MS. Analyze your sample according to your assignment sheet and prepare it as per the instructions on Sample Preparation in the Lab Guide.

3 Final Report: In your final lab report include all thin layer chromatography plates (taped into your notebook) and spectral data on your product. If you obtained an NMR spectrum of your product, compare your spectrum to the NMR included in this handout. If you obtained an IR spectrum of your product, compare your spectrum with the IR included in this handout. Evaluate these carefully with respect to detecting unreacted starting material still present in the product. Questions to be answered at the end of the Final Report: 1. A sample of isoborneol prepared by reduction of camphor was analyzed by infrared spectroscopy and showed a band at 1760 cm -1. This result was unexpected. Why? 2. Would you expect to get the same product by oxidizing isoborneol instead of borneol? Explain. References: Markgraf, J.H. "Stereochemical Correlations in the Camphor Series." Journal of Chemical Education, 44 (1967): 36. Mohrig, J.R., Neinhuis, C.F., Van Zoeren, C., Fox, B.G., and Mahaffy, P.G. "The Design of Laboratory Experiments in the 1980's." Journal of Chemical Education, 62 (1985): 519.

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