Steam Distillation of Essential Oils-Anethole from Anise Followed by Permanganate Oxidation to Anisic Acid The iteam dictillotlm of anise to piw onr!hdr had I w c r m c 1111ppul.3r:n UUI. mdtr.r;iauatc .rganw Ial,ornl*vv due to thc aiffirult\ 11, chralntn.: the d i l w m i d r d r n v n t i ~ ein rcawndl,l\ ptrr f mn: Tu h!p,t+~thi* prs~hlem.w . ~ ~ p l 1111. rd experiment to the permanginate oxidation of an alkyl benzene which converts anethole to anisic acid lp-methoxyhenzoic acid) in good yield. Moreover, anisic acid recrystallizes beautifully from water and can easily he microsublimed on a Fisher-Johns Melting Point Apparatus by sandwiching a few milligrams of product between one glass disc on the hot stage and a glass microscope slide (as a cover) onto which the aeid sublimes. A procedure for the oxidation is given helow. Dissolve 250 mgof anethole in 5 ml of p-dioxane. lntoa 50-ml round bottomed flask, place 1 g of KMn04,20 ml of water, and a boiling chip. Swirl for 30 sec. Add the anetholelp-dioxane solution and swirl for 30 sec. Attach s reflux condenser and heat a t reflux for 20 mi". Let cool t o room temperature, then acidify with 1 M H2S04.T h e anisic acid should precipitate. If some MnOz isstill evident (brown precipitate), add 1 g of NaHSOs while swirling. Separate the solid acid via suction filtration or, alternatively, extract the anisic aeid with methylene chloride. Recrystallize from water and/or suhlime. The oxidation has been run on as little as 100 mg of essential oil with goad results and dramatizes the important oxidation of an alkyl side chain in aromatic compounds. Anisaldehyde, which may be present in the essential oil, oxidizes to anisic aeid under these conditions. Since freshly ground spices dry out after same time, we have resorted to spiking our old spice samples with pure anethole. 1 Moore, J. A,, and Dalrymple, D. L., "Experimental Methods in Organic Chemistry" 2nd Ed., W. B. Saunders Co., Philadelphia, 1976, p. 77.
University of Missouri-St. St. Louis, M O 63121
Louis
138 / Journal of Chemical Education
David L. G a r i n
