Carboxylic acid from ozonides

Dimethyl sulfoxide Aldehydes and carboxylic acids from ozonides... 

Carboxylic acids from ethylene derivatives via ozonides... 

Aldehydes are easily oxidized to carboxylic acids under conditions of ozonide hydroly SIS 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 oxi dants 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 m methanol with reduction by dimethyl sulfide (CH3SCH3)... 

The zwitterion (59) is thereby prevented from reacting with the ketone (58) to form the ozonide in the normal way, and both (58) and (60) may now be isolated and identified. In preparative ozonolysis it is important to decompose the ozonide (57a) by a suitable reductive process, as otherwise H202 is produced (on decomposition of the ozonide with H20, for example) which can further oxidise sensitive carbonyl compounds, e.g. aldehydes— carboxylic acids. 

NOC1 and an alcohol 9-9 From ozonides 9-10 Oxidative cleavage of enol ethers 9-13 Reaction between carboxylic acids and lead tetraacetate 9-18 Oxidation of ethers 9-22 Oxidation of primary alcohols or aldehydes... 

No cross ozonide was formed from unsymmetrical alkenes. The authors theorized628 that the carbonyl oxide zwitterionic species formed on wet silica gel immediately adds water followed by rapid decomposition of the intermediate hydroxyalkyl hydroperoxide to carboxylic acid and water. It means that water on silica gel acts as participating solvent. In the absence of adsorbed water, rapid recombination of the adsorbed aldehyde and carbonyl oxide due to a favorable proximity effect gives normal ozonide. The low mobility of adsorbed species on the silica surface accounts for the absence of cross ozonides. 

An alternative procedure for decomposing ozonides from di- or trisubstituted alkenes is to treat them with methanol (CH3OH). The use of this reagent results in the formation of an aldehyde or ketone and a carboxylic acid ... 

On an industrial scale, the traditional method for cleavage of carbon-carbon double bonds is ozonolysis, used for the manufacture of azelaic acid and nonanoic acids from oleic acid, and of butane tetracarboxylic acid from tetrahydrophthalic anhydride. The process is effectively a quantitative and mild process.178 However, it is capital and energy intensive. The intermediate ozonide is worked up either reductively or oxidatively to produce the aldehyde, ketone or carboxylic acid. Hydrogen peroxide is the common oxidizing agent used in the second step.179-181 Oxygen can also be used either alone182 or in combination with zeolites.183 Reviews on ozonolysis are available and the reader is directed to reference 184 for further information. 

The determination of the active oxygen in ozonides with sodium iodide in glacial acetic acid gives reliable values only in the case of ketozonides. The reaction products are ketones.96 Iodometric peroxide determination in the case of aldozonides gives less than 60% of the theoretical value 112 carboxylic acids are formed as well as aldehydes. The reduction with iodide ions probably suffers competition from the reaction shown in Eq. (7). 

If only one molecule of a carboxylic acid is expected from the ozon-olysis, boiling the ozonide with acetic acid is sufficient, because the ozonide contains one atom of oxygen necessary for such oxidation. 

To convert olefins into carboxylic acids in this way it is preferable to oxidize the primary fission products of the ozonide in a subsidiary reaction. Particularly good results were obtained by Asinger using a hot suspension of silver oxide116 and by Wilms using peracetic acid 117 Wilms thus obtained adipic acid in yields of about 90% from cyclohexene ... 

The intermediate from this initial attack on a double bond is an ozonide as shown generally in Figure 1. Due to the high oxygen content of this intermediate, it is not stable and spontaneously decomposes to a mixture of carbonyl compounds. Various carboxylic acid and aldehyde derivatives of vegetable oils have been prepared in the past by such ozonolysis reactions and this process was commercialized by Emery Industries to manufacture azelaic and pelargonic acids from oleic acid. ... 

---