2.4- Dinitrophenylhydrazones ozonization

Ozonolysis of cis-3,4-Dimethyl-3 -hexene. A solution of cis-3,4-di-methyl-3-hexene (98% pure, Chemical Samples Co.) (1.12 grams, 10 mmoles) in 50 ml pentane was ozonized at — 62°C until the blue color of excess ozone was evident. A nitrogen stream was used to purge the solution of excess ozone. Pentane was then carefully distilled off at atmospheric pressure. A water aspirator (20 mm Hg) was then used to remove the ketone product. Treatment of this material with 10 ml of an 0.1 M solution of 2,4-dinitrophenylhydrazine gave 2.33 grams of crude 2,4-dinitrophenylhydrazone. The crude product was recrystallized and identified as the 2,4-dinitrophenylhydrazone of methyl ethyl ketone, mp 115-116°C. Yield of the ketone was 92% based on olefin used. 

It can thus be seen that zwitterions IV and V would be stabilized by the interaction of the alcohol with them, and the ozonide would have no opportunity to form and decompose abnormally. Whether zwitterions IV and V are formed in equal amounts depends upon the groups which are attached to the double bond and the carbon atom to which the ozone molecule initially adds. The final products, VI and VII, may be considered as hemiperacetals or hemiperketals and could be isolated only under special conditions. However, they can be easily decomposed with either sulfurous acid or sodium bisulfite and the ketones or aldehydes formed determined quantitatively as their 2,4-dinitrophenylhydrazones. 

Several representative compounds from which abnormal products had been previously isolated in ozonizations carried out by other investigators were selected to test the above theory. Ozonizations were carried out in pure methanolic solutions at about —20° C. and in each case the yield of peroxide, based on the ozone consumed, was determined quantitatively. Overozonization was avoided, inasmuch as excess ozone is known to cause side reactions or decomposition of the peroxides (5). The peroxides thus formed were reduced with aqueous sodium bisulfite and the carbonyl compounds isolated as their 2,4-dinitrophenylhydrazones, which were separated quantitatively by chromatography through a mixture (2 to 1) of silica gel and Celite. In no case were any of the abnormal products found. The results are summarized in Table I. 

From Geraniol. The geraniol used was purified in accordance with the method of Knights and Waight (5) and ozonized in pure methanol in the usual manner. The mixture of 2,4-dinitrophenylhydrazones obtained after reduction with sodium bisulfite was extracted with hot ethanol and the solvent removed. The residue was recrystallized from aqueous ethanol yield of acetone 2,4-dinitrophenylhydrazone, 40.8% melting point, 123-4° C. 

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