Ozonolysis products

But their instability makes it difficult to prepare them in good yields and to use them safely in reactions. Ozonides or ozonolysis products have at times expld on standing. Ozonolysis products are also thermally unstable. One must maintain the reaction at a certain temp in order to prepare and react these compds. Moreover, since the ozone addition reaction is highly exothermic, reactors must be cooled to maintain the desired temp (Ref 4)... 

The location of the position of double bonds in alkenes or similar compounds is a difficult process when only very small amounts of sample are available [712,713]. Hass spectrometry is often unsuited for this purpose unless the position of the double bond is fixed by derivatization. Oxidation of the double bond to either an ozonide or cis-diol, or formation of a methoxy or epoxide derivative, can be carried out on micrograms to nanograms of sample [713-716]. Single peaks can be trapped in a cooled section of a capillary tube and derivatized within the trap for reinjection. Ozonolysis is simple to carry out and occurs sufficiently rapidly that reaction temperatures of -70 C are common [436,705,707,713-717]. Several micro-ozonolysis. apparatuses are commercially available or can be readily assembled in the laboratory using standard equipment and a Tesla coil (vacuum tester) to generate the ozone. Reaction yields of ozonolysis products are typically 70 to 95t, although structures such as... 

Ozonolysis of organic compounds in water also has biological and environmental93 interest. Ozone preferentially attacks the base moiety of pyrimidine nucleotides in water.94 For example, the reaction of ozone with uracil in water, having no substitutent at 1-position, gave the ozonolysis products in Scheme 3.6.95 The reactions of DNA and RNA with O3 in an aqueous environment are linked to the damage of... 

Most of the concern for the toxicity of the atmospheres associated with fires has focused on vapors and gases. Vapors and gases are the components that are known to cause acute toxicity, and at high concentrations can lead to incapacitation and death. It is clear, however, that the smokes from fires also have particulate components in the form of soot and chemical reaction products, such as metallic oxides or ozonolysis products. The toxicity of these materials must also be considered. 

Chemical/Physical. Ozonolysis of acrylonitrile in the liquid phase yielded formaldehyde and the tentatively identified compound glyoxal, an epoxide of acrylonitrile and acetamide. The reported rate constant for the reaction of acrylonitrile and ozone in the gas phase is 1.38 x lO cm moFsec (Munshi et al., 1989). In the gas phase, cyanoethylene oxide was reported as an ozonolysis product... 

Chemical/Physical. Ozonolysis products reported are p-quinone and dibasic acids (Verschueren, 1983). Moussavi (1979) studied the autoxidation of hydroquinone in slightly alkaline (pH 7 to 9) aqueous solutions at room temperature. The oxidation of hydroquinone by oxygen followed first-order kinetics that yielded hydrogen peroxide and / -quinone as products. At pH values of 7.0, 8.0, and 9.0, the calculated half-lives of this reaction were 111, 41, and 0.84 h, respectively (Moussavi, 1979). 

On an exam you may be asked to determine the structural formula of the starting alkene given the ozonolysis products. A useful technique is to work backward from the products of ozonolysis. By cutting off the oxygens and then combining the two pieces, you get the starting alkene. 

Burris N (1983) Three-, six- and nine-carbon ozonolysis products from cottonseed oil and crudechlorella lipids. J Am Oil Chem Soc 60(4) 806-811... 

Oxidation of Ozonolysis Products from 1-Octene and 1-Methyl-cyclopentene. Uncatalyzed autoxidation was performed in a small vessel... 

Problem 8.37 For the conjugated and isolated dienes of molecular formula C H, tabulate (a) structural formula and lUPAC name, (b) possible geometric isomers, (c) ozonolysis products. 

The isomers are hexadienes. An allene or alkyne is not possible since CO and RCOOH are not ozonolysis products. Absorption at 175 nm is attributed to the isolated 1,4-hexadiene. The conjugated cis- and trans-1,3-hexadienes absorb at 211 and 216 nm, respectively. 

The method here described is based on the reported ozonolysis of phenanthrene in methanol, followed by conversion of the initial ozonolysis product to diphenaldehyde (p. 41), diphenalde-hydic acid, methyl diphenaldehydate (Note 6), and diphenic acid (Note 7). Diphenaldehydic acid has previously been made in low yields by oxidative decomposition of the monohydrazide of diphenic acid.3-4 The presently described method is far superior, not only in yield, but also in simplicity. 

The acid catalyzes formation of the dimethoxy compound from the initial ozonolysis products (see Note 6 of the diphenalde-hyde preparation, p. 42). Compound I forms only slowly in the absence of the hydrochloric acid. 

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. 

The ozonolytic cleavage of cycloalkenes in the presence of methanol produces a chain with an aldehyde and a methoxy hydroperoxide group at the termini.8 The unsymmetrical ozonolysis product is manipulated in several... 

Depending on the alkene cation radical nature, open-chain oxygenation and epoxida-tion take place as well as the formation of other trivial ozonolysis products. Alkylaromatic compounds are also oxidized by ozone via the ion radical mechanism. Ethylbenzene, for example, undergoes ozone attack on the ring (80%) and on the alkyl group (20%). According to kinetic studies, the ozone consumption obeys the chain law (Galstyan et al. 2001). 

The important clue to deducing the structures of A and B is the ozonolysis product C. Remembering that the two carbonyl carbons of C must have been joined by a double bond in the precursor B, we write... 

Warscheid, B. and Hoffmann, T. (2001) On-line measurements of alpha-pinene ozonolysis products using an atmospheric pressure chemical ionization ion-trap mass spectrometer. Atmospheric Environment, 35, 2927-40. 

Given an alkene or cycloalkene (or diene, and so on), write the structures of the expected ozonolysis products. 

Given the structures of ozonolysis products, deduce the structure of the unsaturated hydrocarbon that produced them. 

In the case of compound a, where cis and trans are possible, either isomer gives the same ozonolysis products. 

Similarly, two stable diastereomeric (synjanti) tricyclic ozonides were obtained from bicyclo[9.4.0]pentadec-l(ll)-en-12-one and ozone at — 75 °C in pentane followed by treatment of the ozonolysis product with H2NOMe. Their structures were confirmed by X-ray crystallography (Scheme 41) <2006EJ01978>. 

Enol ethers of 1,2- and 1,3-diketones afford on ozonolysis products that are not in full agreement with the Criegee mechanism, because in some cases products of the Baeyer-Villiger rearrangement are formed. The main product in the ozonolysis of the enol ether 180 is a mixture of spiranic stereoisomers 181 involving a lactone and a 1,2,4-trioxolane ring (Scheme 62) <2004HCA2025>. 

The four related compounds oxalomycin (157), neooxalomycin (158), cur-romycin A (159), and curromycin B (160) were reported in 1985 157 and 158 were isolated from a yet to be identified Streptomyces species (79, 80) and 159 and 160 from an ethidium bromide-treated strain of S. hygroscopicus (81, 82). The absolute configuration of oxalomycin (157) and neooxalomycin (158) has been determined by application of a combination of X-ray crystallography and chemical correlation to degradation products, the important derivatives being the p-bromobenzoate 161, obtained from 157 by ozonolysis-reduction, acetylation, partial hydrolysis, and reacylation with p-bromobenzoyl chloride, and the erythro acetate 162 which was obtained along with the threo compound 163 after acetylation of the ozonolysis products of 157 (79, 80). No stereochemical infor-... 

Evidence (132) in favor of partial structure CXXXIII for C-curarine comes from the ozonolysis of tetrahydronorcurarine, in which only the ethylidene double bonds have been reduced. The UV-spectrum of this tetrahydro product is as that of C-curarine itself, and thus the central part of the molecule (CXXXII or CXXXIII) has been unaffected in the conversion into the tetrahydro derivative. After treatment of the ozonolysis products with active zinc, acid hydrolysis, and finally reduction with sulfur dioxide, the reaction mixture yields strychanone (LXXIV), indicating the 16,17 and 16, 17 positions for the central double bonds of C-curarine as in CXXXIII. It is pointed out, however, that this evidence is not conclusive, and that the illustrated mechanism can be written which would account for the formation of 1 molecule of strychanone from a compound with partial structure CXXXII (132). 

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