Ozonization, aldehydes from

FIGURE 4-4 Nitrogen dioxide, nitric oxide, ozone, aldehyde, and hydrocarbon concentrations in University City, Rome, Italy. Reprinted with permission from nato/ ... 

Procedures. Chromatographic Purification of Ozonization Products. Ozonization products from ethyl 10-undecenoate and 1-octene were chromatographed on silica gel columns (Baker) and eluted with 15 or 25% ether in petroleum ether (b.p., 30°-60°). Fractions were examined by thin-layer chromatography (TLC) on silica gel G Chroma-gram sheet eluted with 40% ether in petroleum ether. For development of ozonide and peroxide spots, 3% KI in 1% aqueous acetic acid spray was better than iodine. The spots (of iodine) faded, but a permanent record was made by Xerox copying. Color of die spots varied from light brown (ozonide) to purple-brown (hydroperoxide), and the rate of development of this color was related to structure (diperoxide > hydroperoxide > ozonide). 2,4-Dinitrophenylhydrazine spray revealed aldehyde spots and also reacted with ozonides and hydroperoxides. Fractions were evaporated at room temperature or below in a rotary evaporator. 

Alkenes are directly oxidized to aldehydes and/or ketones by ozone (O3) at low temperatures (—78 °C) in methylene chloride, followed by the reductive work-up. For example, 2-methyl-2-butene reacts with O3, followed by a reductive work-up to yield acetone and acetaldehyde. This reducing agent prevents aldehyde from oxidation to carboxylic acid. 

HVAC Materials Ventilation duct liners also react with ozone forming formaldehyde, acetone and C5—Ci0 aldehydes. Morrison et al. (1998) subjected new and used duct liners, air filters, sealants, sheet metal and other HVAC materials to ozone in small chambers. They observed secondary emissions of C5—Ci0 aldehydes from a new duct liner, a neoprene gasket and duct sealants. They predicted that secondary emissions from these materials could increase indoor aldehyde concentrations to levels comparable with odor thresholds. As will be discussed later, soiled HVAC materials also generate secondary products. 

Wang, H. and Morrison, G.C. (2006) Ozone initiated secondary emission rates of aldehydes from indoor surfaces in four... 

Strategy Both sets of reactants cleave double bonds. Aqueous KMn04 produces a carboxylic acid from a double bond carbon that is monosubstituted and a ketone from a double bond carbon that is disubstituted. Ozone produces an aldehyde from a double bond carbon that is monosubstituted and a ketone from a double bond carbon that is disubstituted. If the double bond is part of a ring, both carbonyl groups occur in the same product molecule. 

The conversion of tetrasubstituted double bonds to the corresponding ketones is easily achieved using a number of oxidants. However, if one or more of the alkenic carbons is secondary, the product will be either an aldehyde or a carboxylic acid Ozone and a combination of osmium tetroxide and sodium metaperiodate are recommended if the desired product is an aldehyde. Under carefully controlled conditions it is also possible to obtain good yields of the aldehyde when permanganate is used as the oxidant All methods that give aldehydes from secondary carbons can also be used to prepare ketones from tertiary carbons. 

The cleavage of the double bond with ozone was first reported in 1971 by Frechet for the release of aldehydes from the solid-phase carrier. These anchors are described under the heading Miscellaneous anchors cleaved by oxidation . 

It is true that, for instance, one does not find under the keyword aldehyde the preparation of benzaldehyde (a) from toluene by way of benzyl chloride or benzaldehyde dichloride, (b) from benzene and hydrogen cyanide-hydrogen chloride (Gattermann-Koch) or from bromobenzene by way of phenyl-magnesium bromide and formic ester (Grignard), and (c) from stilbene and ozone or from 1,2-diphenyl-1,2-ethanediol and lead tetraacetate but such a collection of syntheses is to be found in the systematic textbooks and reference works of organic chemistry, and the compass of the large reactions remains nevertheless substantially intact in our treatment. 

Although cleavage of the olefinic double bond is not normally observed, as is the case with ozone, a possible cleavage reaction with unsaturated material in natural waters was indicated by the isolation of C2-Cg aliphatic aldehydes from Ohio River water treated with CIO2 (Stevens et al., 1978). Aldehydes, however, are reportedly converted readily to carboxylic acids by CIO2 (Somsen, 1960), so the detailed pathway of this process remains to be worked out. 

The amount of aldehyde groups is usually used for evaluation of the intensity and efficiency (number of chain scissions per molecule of reacted ozone) of ozone degradation of elastomers. In this case, it should be taken into account that the dominant route of degradation leads to the formation of 1 mole of aldehyde from 1 mole of ozone [32]. 

Ozone dimethyl sulfide Aldehydes from ethylene derivatives hy oxidative cleavage... 

We have focused our attention on the solid phase synthesis of such compounds and described our results here. Alternative routes for the preparation of peptide aldehydes and side-chain protected peptide aldehydes in solid phase synthesis are described. Three new linkers that are stable tmder classical Fmoc or Boc strategies have been developed to obtain the peptide aldehyde from the solid support. One of these linkers was conceptualized on the basis of the Weinreb amide (49) and the other on the basis of phenolic esters (50). Both strategies required the reduction with hydrides of the peptide-linker-resin to release the peptidic aldehydic function. The use of these two different approaches was demonstrated by the synthesis of N-protected a-amino-aldehydes and peptide aldehydes, llie third approach used the ozonolysis reaction for the generation of the desired aldehyde. This concept requires a linker incorporating a double bond in the a-position of the asymmetric carbon of the C-terminal residue that will be cleaved by ozone to produce the carbonyl function. 

Ozone pyridine-zinc acetic acid Aldehydes from ethylene derivatives... 

In discussing atmospheric pollution, it is important to make the distinction between primary and secondary air pollutants. Primary air pollutants are those that are pollutants in the form in which they are emitted into the atmosphere. An example would be light-scattering fine ash particles ejected from a smokestack. Secondary air pollutants are those that are formed from other substances by processes in the atmosphere. A prime example of a secondary pollutant develops when otherwise relatively innocuous levels of hydrocarbons (including terpenes from pine and citrus trees) and NO are emitted into the atmosphere and subjected to ultraviolet radiation from the sun, resulting in a noxious mixture of ozone, aldehydes, organic oxidants, and fine particles called photochemical smog. 

Ozonolysis of double bonds as a route to ketones and aldehydes is well known. Thiourea may be used for the reduction of the ozonide to afford aldehydes from suitable alkenes. Electrolytic reduction of ozonization products from the oxidation of trisubstituted cyclic alkenes in acetic acid offers a route to hydroxy-ketones. a-Alkoxy-peroxides, from ozonolysis in alcoholic solution, are stable... 

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)... 

Oxidation. Olefins in general can be oxidized by a variety of reagents ranging from oxygen itself to ozone (qv), hydroperoxides, nitric acid (qv), etc. In some sequences, oxidation is carried out to create a stable product such as 1,2-diols or glycols, aldehydes, ketones, or carboxyUc acids. In other... 

Polymeric OC-Oxygen-Substituted Peroxides. Polymeric peroxides (3) are formed from the following reactions ketone and aldehydes with hydrogen peroxide, ozonization of unsaturated compounds, and dehydration of a-hydroxyalkyl hydroperoxides consequendy, a variety of polymeric peroxides of this type exist. Polymeric peroxides are generally viscous Hquids or amorphous soHds, are difficult to characterize, and are prone to explosive decomp o sition. 

Oxidative degradations of aldehyde derived enamines with ozone (4) or sodium dichromate (485-487) have been applied to the formation of progesterone from 3-ketobisnor-4-cholenaldehyde. 

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