Hydroperoxides from ozonolysis

It must be noted here that ketone or aldehyde, diperoxides and peroxide oligomers are obtained in non participating solvents whereas alkoxy or alkyl hydroperoxides result from ozonolysis conducted in participating solvents [13]. 

The hydroperoxides derived from 1-homoallylindan-l-ols and 1,2,3,4-tetrahydronaphth-l-ols are converted into spiro-linked 1,2-dioxane hydroperoxides on ozonolysis (Scheme 46) <06EJO2174>. 

Ozonolysis of alkenes in participating solvents such as alcohols often leads to trapping of intermediates. Most commonly, an alcohol will react with the carbonyl oxide zwitterion, generated from cycloreversion of the primary ozonide (Section 4.16.8.2), to give an alkoxy hydroperoxide. The secondary ozonide (1,2,4-trioxolane) is usually more stable to nucleophilic attack from alcohols. 

Gab, S E. Hellpointner, W. V. Turner, and F. Korte, Hydroxymethyl hydroperoxide and Bis(hydroxymethyl)-peroxide from Gas Phase Ozonolysis of Naturally Occurring Alkenes, Nature, 316, 535-536 (1985). 

From silanes 52 are obtained, in high yield, the corresponding silanols 53, which react further to produce disiloxanes 56 and 58-60. Silanes 54 alkoxysilanes 55 and disilanes 57 give high yields of disiloxanes 56. Ozonolysis of tetraethylsilane yields initially acetaldehyde and trimethylsilyl hydroperoxide 61. The latter is partially converted to bis(triethylsilyl) peroxide 62, which is hydrolyzed to silanol 63 and hydrogen peroxide. The ozonolysis is of first order, both in regard to the silanes, and to ozone. The ozonolysis starts with formation of 64 followed by formation of the trioxide 65, which decomposes to acetaldehyde and hydroperoxide 61 (Scheme 14)79 80. 

Although the ozonolysis product exists in oligomeric form, the amount of acid used was calculated by assuming a theoretical yield of the corresponding monomeric aldehyde—methoxy hydroperoxide. p-Toluenesulfonic acid monohydrate, purchased from Aldrich Chemical Company, Inc., was not further purified. 

Localization of double bonds in unknown compounds has frequently been determined by ozonolysis. Unsaturated fatty acids of biological membranes are susceptible to ozone attack, but there are some important differences from autoxidation reactions. These include the fact that malonaldehyde is produced from linoleate by ozonolysis (53) but not autoxidation and also that ozonolysis does not cause double bond conjugation as judged by absorption at 233 nm (52). Reactions with the polyunsaturated fatty acids produce several possibilities for toxic reactions direct disruption of membrane integrity and toxic reactions caused by fatty acid hydroperoxides, hydrogen peroxide, and malonaldehyde. 

The oxygen-oxygen bond of peroxides is easily reduced and many standard reducing agents are capable of cleaving the bond efficiently. Catalytic and other methods have been reviewed. Whereas the reduction of hydroperoxides leads to the formation of alcohols, considerable selectivity is possible in the products derived from disubstituted peroxides. Hydroperoxides and disubstituted peroxides are, therefore, discussed separately below, even though some of the reduction methods are identical. Reductive ozonolysis of alkenes has also been included as a separate third category. 

Oxidations. Cleavage of alkenes to aldehydes and ketones is promoted by Wilkinson s catalyst under pressures of air or oxygen, but these reactions are inferior to ozonolysis because they tend to form a mixture of products. More useful are the oxidations of anthracene derivatives to anthraquinones in the presence of oxyg a/tert-Butyl Hydroperoxide and catalytic RhCl(PPh3)3 (eq 54). Wilkinson s catalyst reacts with oxygen to form an adduct so RhCl(PPh3)3 is clearly quite different from the true catalyst in all the reactions mentioned in this section. 

Gab, S., E. Hellpointner, W.V. Turner and F. Korte (1985) Hydroxymethyl hydroperoxide and bis-(hydroxymethyl) peroxide from gas-phase ozonolysis of naturally occuring alkenes. Nature 316, 535-536... 

Preparation of Block Copolymers from Macroinitiators. In an early paper, Ceresa reported polymerization of methyl methacrylate in the presence of oxygen, and then swelling the polymer with styrene. On heating, the polymeric peroxide decomposed initiating styrene polymerization thus forming a block copolymer(89). Even earlier, macroperoxides, useful in the preparation of block copolymers, were prepared by initiating the polymerization of butadiene with m-diisopropyl benzene dihydroperoxide in an emulsion. On further heating in the presence of styrene and Fell salts, a block copolymer was formed l Recently in independent work, polypropylene hydroperoxide was prepared by ozonolysis, and with triethylenetetra-amine as an activator was used to initiate block addition of styrene(91) and other vinyl monomers(92,93). ... 

---