Ozonides hydrolysis

Aldehydes are easily oxidized to carboxylic acids under conditions of ozonide hydrolysis. When one wishes to isolate the aldehyde itself, a reducing agent such as zinc is included during the hydrolysis step. Zinc reduces the ozonide and reacts with any oxidants present (excess ozone and hydrogen peroxide) to prevent them from oxidizing any aldehyde formed. An alternative, more modem technique follows ozone treatment of the alkene in methanol with reduction by dimethyl sulfide (CH3SCH3). 

Tab. 5.3 Direct comparison of ozonide hydrolysis between solution-phase, solid-phase and liquid-phase triphenylphosphine.

Because hydrogen peroxide is a product of ozonide hydrolysis and has the potential to oxidize the products, the second half of this two-stage ozonolysis sequence is carried out in the presence of a reducing agent, usually zinc or dimethyl sulfide. 

Ozonides undergo hydrolysis in water giving carbonyl compounds... 

This cleavage reaction is more often seen in structural analysis than in synthesis The substitution pattern around a dou ble bond is revealed by identifying the carbonyl containing compounds that make up the product Hydrolysis of the ozonide intermediate in the presence of zinc (reductive workup) permits aide hyde products to be isolated without further oxidation... 

Commercially, pure ozonides generally are not isolated or handled because of the explosive nature of lower molecular weight species. Ozonides can be hydrolyzed or reduced (eg, by Zn/CH COOH) to aldehydes and/or ketones. Hydrolysis of the cycHc bisperoxide (8) gives similar products. Catalytic (Pt/excess H2) or hydride (eg, LiAlH reduction of (7) provides alcohols. Oxidation (O2, H2O2, peracids) leads to ketones and/or carboxyUc acids. Ozonides also can be catalyticaHy converted to amines by NH and H2. Reaction with an alcohol and anhydrous HCl gives carboxyUc esters. 

This discussion of the structures of diene polymers would be incomplete without reference to the important contributions which have accrued from applications of the ozone degradation method. An important feature of the structure which lies beyond the province of spectral measurements, namely, the orientation of successive units in the chain, is amenable to elucidation by identification of the products of ozone cleavage. The early experiments of Harries on the determination of the structures of natural rubber, gutta-percha, and synthetic diene polymers through the use of this method are classics in polymer structure determination. On hydrolysis of the ozonide of natural rubber, perferably in the presence of hydrogen peroxide, carbon atoms which were doubly bonded prior to formation of the ozonide... 

Hydrolysis, or better, hydrogenolysis of the normal ozonide leads to the cleavage of the original carbon-carbon double bond with formation of carbonyl groups. The abnormal ozonide usually decomposes before it reaches room temperature and both the double bond and the adjacent carbon-carbon single bond are found to have cleaved. 

The ozonides of choline and ethanolamine phosphatides subjected to reduction with PhsP yield the corresponding core aldehydes. After hydrolysis with phospholipase C to eliminate the polar group and silylation with trimethylsilyl chloride, the core aldehydes can be determined by GLC-FID using temperature programming to high temperatures . ... 

O 16.14% crysts (from acet, benz or ethyl acetate), mp 206.5-07.5° 214.5-15.5°, de-pending on cryst size, rate of heating solv used fairly sol in hot benz CCI4 diffc sol in eth, acet, eth acet acet ac insol in ale was obtd by ozonolysis of 1,1-diphenyl-l-alkenes In CCI4 and hydrolysis of the ozonide No expin of this compd occurred when heated to its mp, but when heated for 5 mins at 214-15°, it decompd comjietely to benzo-phenone... 

Oxidative hydrolysis transforms the intermediate ozonide into ketone(s) and/or carboxylic acid(s) in good yields. H202 in water, in sodium hydroxide solution, or in formic acid is the best proven oxidant.582,584,592 Peroxy acids and silver oxide are also employed. Rearrangement and overoxidation may be undesirable side-reactions. A simple two-step ozonation in MeOH yields methyl esters without added oxidizing agent.627... 

These substances, like most compounds with peroxide (O—O) bonds, may explode violently and unpredictably. Therefore ozonizations must be carried out with appropriate caution. The general importance of these reactions derives not from the ozonides, which usually are not isolated, but from their subsequent products. The ozonides can be converted by hydrolysis with water and reduction, with hydrogen (palladium catalyst) or with zinc and acid, to carbonyl compounds that can be isolated and identified. For example, 2-butene... 

In order to prevent the oxidation of the aldehyde groups to the acids, it is necessary to use some means to remove the hydrogen peroxide formed during the hydrolysis of the ozonide. Hurd and Filachione170 carried out the hydrolysis in pyruvic acid. Other workers171-17 have used zinc dust in this step, and hydrogenation with platinum as a catalyst177 has been mentioned in connection with hydrocarbons. 

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