JOURNAL OF CHEMICAL EDUCATION
A PORTABLE SEMIMICRO OZONIZER WILLIAM A. BONNER Stanford University, Stanford, California
THEozonization reaction has heeu described (1) as the most general and reliable procedure for double-bond cleavage and location, in that the primary cleavage products are formed under conditions wherein the excess of oxidant does not affect them. In this respect ozonization offers distinct advantages over degradations employiug alternative oxidants. For conducting osonizations on a laboratory scale, a number of ozonizer designs have been described in the recent literature (H?), the most detailed description of apparatus and procedure being given by Smith and co-workers (7). The ozonizers previously described are designed primarily for macro-ozonization, and usually ha1.e the
necessary disadvantage of being rather cumbersome, complex to construct, and immobile. Because of these features alternative degradation procedures are usually considered before ozonization, and the latter reaction has not achieved as videspread use as a research and teaching tool as might he warranted. Experimental familiarity with ozonization is rarely part of the background of the graduate student, much less the undergraduate. To obviate some of these drawbacks we wish to describe a compact, portable, inexpensive apparatus for conducting ozonization simply and rapidly on a semimicro scale. The semimicro ozonizer consists of four Pyrex units,
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a bubbler for control of oxygen throughput, a singleunit Berthelot tube for generation of the ozone, a reaction flask to hold the substance to be ozonized, and a soda-lime tube (8) for decomposition of excess ozone. The Berthelot tube contains a central finger filled with copper sulfate solution and connected by a copper wire to the high-voltage terminal of a transformer. A grounded tape-wrapped aluminum foil covering about t,he exterior of the Berthelot tuhe provides the second electrode. A 115-v. primary, 10,000-v. secondary ignition transformer (Jefferson Electric Co., Bellwood, Ill; Cat. No. 638-171) serves satisfactorily as the high-voltage source providing silent electrical discharge, although a two-inch induction coil operated from a 6-v. transformer has also given satisfactory results. As a precaution, all high-voltage connections are heavily insulated with rubber tape, and the lead to the top electrode is covered with heavy Tygon tubing. A glass stopper above the inlet to the ozonization flask provides for cleaning the inlet tuhe. The soda-lime ozone destroyer acts with an efficiency which precludes the need to employ the apparatus under a hood. The dimensions and other construction details of the apparatus are shown in the drawing. Since the ozonizer is designed for semimicro nse where ozone yield is unimportant, and since the production of ozone is strongly dependent upon voltage and oxygen throughput (7), no attempt has been made to determine the percentage of ozone in the effluentstream. With a moderate oxygen flow rate, however, we have ozonized a millimol of olefinic material in as little as five minutes with the apparatus shown. The facile use of this ozonizer is greatly enhanced by conducting the ozonization of the olefin in the presence of alcoholic 2,4-dinitrophenylhydrazine sulfate solution (9) after the general procedure of Tatum (8). Under these conditions the olefm ozonide is decomposed a,s it, is produced, and the 2,4-dinitrophenylhydrazones of the carbonyl degradation products are immediately obtained in high yield. This procedure makes qualitative detection of olefinic unsaturation rapidly possible under conditions where the Baeyer test with permanganate, or the qualitative hromination test is slow or ambiguous (10). Tatum's procedure also suggests other ready uses for the present equipment. Since the carhonyl derivative is isolatable at the outset in a state of acceptable purity, immediate identification of the cleavage fragments sometimes is possible by mere melting-point determination. If a broad meltingpoint range for the derivative is obtained, the prohahility of an unsymmetrical olefin is indicated. Depending on solubility characteristics of the derivatives, however, a sharp melting point may or may not be obtained on ozonization of an unsymmetrical olefin. Thus on ozonization in 2.4dinitronhenvlhvdrazine . " " solution, styrene produces benzaldehyde 2,4-dinitropheuylhydrazone of correct melting point whereas triphenylethylene gives a crude derivative of broad and indistinct melting point. The rapid and high-yield
nature of the reaction also permits 2,4-dinitrophenylhydrazone formation to he used as a criterion for the duration of ozonization required for a particular olefin. ACKNOWLEDGMENT
The author is indebted to Mr. Tony Zurek of the Oak Ridge National Laboratory for the glass construction of the ozonizer shown, and to the Chemistry Division of Oak Ridge National Laboratory for certain technical assistance. LITERATURE CITED (1) GILMAN, H., "Organic Chemistry," 2nd ed., John Wiley R. Sons, Inc., New York, 1943, Vol. I, p. 636. (2) JACQUEMAIN, R. P., AND G. B.U,LOUE,B d l . Soe. Chim., ( 5 ) 3,701 (1936). (3) SHEEHAN, W., AND W. CARLIODY, Ind. Enp. Chem.,Anal. Ed.. 9.8 119371. ' (4) Goss, ?A. J., AND M. P H I I ~ PJ. S ,ASSOC.OffLeialA97. Chem., 21.326 --,.-.ilQRR\~ ~ (5) UHRIG,K., J. CHEM.EDUC.,22, 582 (1945). (6) EGERTON HUMAN, J. R., Chemistry &Industry, 1946, 188. (7) SMITH,L. I., F. I,. GREEIYIVORD, . 0. HUDRLIK, OT~. Szmlheses, 26, 63 (1946) (8) E.. L... . mivat? communication of work t o be oub. . TAT~M lished. (9) SHRINER, R. L., AND R. C. FUSOS,,'The Systematic Identification of Organic Compounds." 2nd ed., .John Wiley B Sans, New York, 1940, p. 65. ( l o ) bid., p. 39.
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