The Odor of Optical Isomers-An
Amendment
We report our modification of Momv and Pickering's excellent experiment (J. CHEM. EDUC., 50, 74 (1973)) in which we utilize column chromatography on Silica Gel to separate the components of the oils. Each student has 2 g of oil t o chromatograph. The column is simply made by pulling glass tubing (22 mm ad) of length 35 em. A short l e w t h of rubber tubing with a spring clamp acts as a tap. In this way the cast of each column is mtni~nnl An insrrurtur drmonstratri thr parking ui the culumn wrth 25 e ot Silica Gel as a prrrolcum ether ib p. la-90'C slurry. The top uf the gel is protected hy 1 rm ot sand Afrcr n d d ~ t ~ o01'nthe neat oil to the top ai the column, pcrroleum rrher ~i added such that 25-RU rnl are rollcrred. Then Ill% dichlonmrthme, ucrrnleum -the, i-added end aiurther 5,-GO ml collected. This fraction contains the limonene, which may be retained far alkene tests. A third fraction of 25 ml is collected using 20% diehlommethane-petroleum ether and is discarded as it contains small amounts of carvane and limonene. Finally 1:1 dichloromethane-petroleum ether is added and 100-130 ml collected. Thls fraction contains most of the cawone. The fractions are evaporated by standing them in a hot water bath in a hood; the students then compare samples by meansof ir and nmr spectroscopy, tlc or glc. The preparative part of the experiment takes only 1-1%hr, and thus the comparison can be completed in one 3-hr period. R. H. Mitchell P. R. West
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University of Victoria Victoria, B.C. Canada
274
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Journal of Chemical Education
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