Steam Distillation of Essential Oils-Carvone
from Caraway
The steam distillation of essential oils from natural products is a popular experiment for both organic chemistry and general chemistry laboratories.' We have been using freshly p o u n d spices for this purpose in our introductory organic laboratory. Strictly for economic, reasons, we investigated the use of caraway seeds 9s starting material (at less than $lilb. the cost is en. ldstudentL2The essential oil was isolated by standard techniques. The results were extremely .z..+ifliino m.......,...hin ... t h d" (a) we obtained yields of 5.6% of oil based on the weight of plant material (h) the oil is predominantly d-earrone major, and limonene (minor) which can be readily analymd by vpc (VI hirh melting derivatives of earvone ran be readily. prepared and purified (aem~earbazoneand 2,4.DNP) . . i-&one can be isolated from spearmint leaves or supplied by the instructor t o introduce the concept of ootieal activitv in the laboratow. The fact that the enantiomers can he differentiated hv odor heirhtens student interest in thr topic and ruggests further expertmentation to expound on the ~ u h j e r t ?For example, acomparijon of the ennntiomers via ra) their .peetral properties. ih) thew optical rotslionr, and (othe melting points and mixed melting point* of their respective semir~rhalonsaloads to a more thorough understanding of optical iromerism.
oreo over,
'Mmre, J. A., and Ddrymple. D. L., "Expsrimmtal Math& in Organb Chemi8W, W. B. Saundera Ca., Philadelphia, 1971, p. 65. Nehon, K. L,and Thornpaon, E.,"LaborstoryProjeeta in Ckgmic Chemistry," Allyn & Bacon,Emton. 1966, p. 106. MeCullough. T.. J. CHEM. EDUC., 49,@38 (1972). Graenbcrg, F H.,J.CHEM.EDUC..45,537 (1966). We have obtained om mound apices from Spimrdt Inc., 910 Spruce S t , St. Lou., Mi.aouri. who ware kindlyraillingtoaupply m with leu than the" minimum order .equiremenrs. Murou, S. L., and Pickering, M., J. CHEM. EDUC., 50.74 (1973).
University of Missouri-St. Louis St. Louis. 63121
David L. G a r i n
Volume 53, Number 2,February 1976 / 105
