Oxidation of aliphatic compounds

Irradiation of optically pure (l/ ,25 )-(+)-cw-chrysanthemol (22) in the presence of dicyanobenzene as an electron acceptor leads to the formation of (/ )-5-(l-(p-cyanophenyl)-l-methylethyl)-2,2-dimethyloxacyclohex-3-ene (23 Ar = p-cyano-phenyl). The success of this reaction depends upon the relief of ring strain which can be rationalised in terms of nucleophilic attack of the radical cation on the terminal carbon of the vinyl group, and simultaneous replacement of the isopropyl radical as an intramolecular leaving group in an 8 2 reaction. 

Anaerobic photooxidation of a range of aliphatic carboxylic acids using iron(III) tetra(2-N-methylpyridyl)porphyrin has been described and the primary step reported to be photoreduction of the Fe(III) atom by the axial carboxylate ligand to give a solvent caged [RCO Fe(II)porphyrin] species. The rate of the reaction is determined by competitive reactions of RCO2 in the solvent cage. 

Irradiation of 2-phenylcyclopropanone methyl tert-butyldimethylsilyl acetal in the presence of either phenanthrene or pyrene as redox photosensitiser and dimethyl fumarate as radical acceptor, gives a mixture of the cross-coupled 

Photolysis of ring-substituted phenacyl bromides gives ketyl radicals which in the presence of alcohols leads to the corresponding carbonyl compounds.Two different chain mechanisms seem to operate and in the presence of methanol, oxidation predominantly occurs by hydrogen transfer whereas in the presence of isopropanol, acetone is formed mainly by an electron transfer process. 

6 Oxidation of Aliphatic Compounds Photooxidation of C, C , aund C cycloalkames has been 

4- dihydro-2H-pyran using various cyauio6u ithracenes has been 

4- dihydro-6-methyl-2H-pyran-5-carboxylic acid ethyl ester, 

2- (phenoxymethylidene)adaunantane and other enol ethers have been 

1 Oxidation of Aliphatic Compounds. - A general review of the use of supra-molecular systems as microreactors for photochemical reactions contains a section dealing with the photosensitized oxidation of alkenes included in zeolites, nation membranes and vesicles. Particular consideration is given to the possibility of controlling the form and environment of the sensitizer and substrate so that the reaction selectively follows an energy-transfer or an ET pathway. The same authors have also provided a more substantial review on the same theme. Recent developments in relation to the stereochemistry and mechanism of the ene photooxygenation of alkenes by O2 have also been reviewed.  

CftH 14/NaY-methylene blue C5F14/NaY-methy lene blue 

4-trioxane ring system is the key structural subunit in a number of substances with promising anti-malarial activity, and has been constructed by a number of groups using a photooxygenation approach. Thus the readily available allylic alcohol geraniol reacts with O2 to give a mixture of mono- and 

A number of other reports relating to 02 chemistry have appeared. The discovery of a new monooxide of fullerene, a [5,6]-open oxidoannulene, and the suggestion that a careful re-examination of all product mixtures obtained by oxidizing [60]fullerene would show that this material was a standard product of such reactions, has led to a re-investigation of the photooxygenation of [60]-fullerene. HPLC and C-NMR analysis of the product obtained, however, failed to detect any trace of the new monooxide. The photo-oxidation of the enol ether (101) has been considered as part of a comparative study which also 

Kinetic data have been published for the photo-oxidation of air-saturated cyclohexane, and a radical mechanism has been described to explain the results. 

Photoinitiated free-radical chlorination of (10) using phenyliodine dichloride is directed exclusively to the C(9) position, probably as a result of the conformation of the steroid placing the C(l) complexed to the template iodine atom close to the C(9) hydrogen. Dehydrochlorination then places a double bond in the C(9)-C(l) position. 

Inoue T. Hakushi, and N. J. Turro, Kokagaku Toronkai Koen Yoshishu, 1979, 150. Y. Inou and N. J. Turro, Tetrahedron Lett., 1980, 21, 4327. 

The stereoselective addition of singlet oxygen to the 8-isopropylidenetricyclo-[3.2.1.0 ]octanes (20) and (21) has been discussed in terms of Walsh and n 

Singlet oxygenation of cw,c -cyclo-octa-l,5-diene produces 6-hydroperoxy-cyclo-octa-1,4-diene and on further oxidation 5,8-dihydroperoxycyclo-octa-1,3-diene. Since reduction of this hydroperoxide with PhaP leads to cw-5,8-dihydroxy-cyclo-octa-1,3-diene, the whole sequence represents a convenient synthetic entry into 5,8-difunctionalized oxygen derivatives of cyclo-octa-1,3-diene. A highly stereoselective method has been developed for the cw-oxygenation of cycloheptyl systems. This involves irradiation of methanolic solutions of 1-acetoxy-cyclohepta-3,5-diene in the presence of haematoporphyrin as sensitizer to give 

Cu(II) and Cu(I) species adsorbed on the surface of TiO2. 0 Irradiation of sugar esters of aliphatic acids in aqueous HMPT promotes their photooxygenation in a process which is initiated by the photoionisation of HMPT.l ii The solvated electron reduces the ester to its radical anion which in turn forms the deoxysugar. Arrhenius parameters for H-abstraction have been obtained in a kinetic study of the reaction of 0(3P) atoms. 2 nje activation energy for H-abstraction from C-H adjacent to carbonyl is found to be slightly greater than that fiom the same kind of C-H bond which is nonadjacent. 

There continues to be considerable interest in the effect of the reaction medium on the outcome of 62 oxidations. The photo-oxidation of hydrocarbons in cation-exchanged zeolites has been the subject of a review in which the authors focus on their work in this area and assess the industrial potential of these reactions. The examples provided in another review emphasize that the 

Methane and ethane have been photooxidised to the corresponding aldehydes using a solid-supported vanadium oxide catalyst, V205/S102-IW (incipient wetness) at elevated temperatures.Both processes are highly sensitive to reaction temperature and to the method by which the catalyst is prepared. 

Irradiation of oxygenated solutions of a-terpinene (56) in the presence of perylene diimide or 9,10-dicyanoanthracene leads to the formation of p-cymene (57) in a process which occurs by an exciplex rather than by 02( Ag) pathways. Hydroperoxy radicals may be involved in a quantum yield amplification process, and it is speculated that O2 quenching of the exciplex, or proton transfer within the exciplex, followed by trapping of the semi-reduced perylene diimide by molecular oxygen are possibilities. 

H2C CMeC(CMe3)(OH)CH CHCMc20H, which would have arisen from allylic hydrogen abstraction. This implies that the higher reactivity of the vinyl hydrogen can be rationalised in terms of the large orbital interaction 

Co-adsorption of aliphatic and aromatic aldehydes and molecular oxygen on reduced Ti02 surfaces, followed by UV irradiation at low temperature, 

Photooxidation rates of propan-2-ol in aqueous Ti02 suspensions are reported to be increased by ultrasound radiation, an observation which has been rationalised in terms of mass transport of the substrate and activation of the solid catalyst. The value of the newly described photochemical rearrangement of 2-phenylthio-l,3-cyclohexanediols such as (69) to deoxysugars (70) which are in equilibrium with the closed form (71) has been illustrated by its application to the synthesis of (+)-m-rose oxide (72), and the same authors have also described the regioselective photorearrangement of 2-phenylthio-3-aminocyclohexanols (73) to deoxyazasugars (74) this has proved to be useful in the synthesis of various piperidines (75), amino-sulfones, -sulfoxides and -acids. Hydroxy(alkoxy)methyl radicals have been generated by photo-induced electron transfer.  

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Kinetic Isotope Effect in Oxidation of Aliphatic Compounds by Ozone... 

Reactivity of organic compounds toward HO is estimated readily in most cases because of the large databases of values measured for reactions in water and air and the correlation equations relating rates of oxidation of aliphatic compounds in air and water, as well as the availability of Hammett SARs for reactions of aromatic compounds. In addition, 90% of HO rate constants in water and air are within 50% of 5 x 109 M 1 s Thus, the limiting indirect photoreaction rate constant for almost any compound in freshwater with more than 1 mg/L of NO3 will be 1.5 x 10 7 s 1 at 40°-50° latitude in summer, equivalent to a 50-day half life. In low-nitrate waters, the limiting half life will be extended correspondingly. 

Gerhold, R.M., Malaney, G.W. (1966) Structural determinants in the oxidation of aliphatic compounds by activated sludge. J. Water Pollut. Control Fed. 38, 562-579. 

Oxidation of Aliphatic Compounds Alkfuies have been photoox id ised in aqueous solutions of Hg(II) salts and their use on a preparative scale described. An experimental study and theoretical modelling of methane CH bond photoactivation by M0O3 and Cu -doped M0O3 has appeared and cyclohexane and 1,4-dimethylcyclohex5me have been... 

Oxidation of Aliphatic Compounds. - This area, understandably, continues to be dominated by the use of heterogeneous photo-oxidation systems in general and Ti02 in particular. These systems are used both for non-selective photodegradation, or in pursuit of a selective, synthetically useful transformation. In terms of photodegradation, a method of predicting the rate constants for the catalytic... 

Pulsed amperometric detection is used for the direct detection of a variety of polar aliphatic compounds, many of which, like carbohydrates, peptides and sulfur-containing compounds are of biological interest [171,197-200]. Most aliphatic compounds are not amenable to constant potential amperometric detection. Free-radical products from the oxidation of aromatic molecules can be stabilized by it-resonance hence the activation barrier for reaction is decreased. This mechanism is unavailable for stabilizing aliphatic free radicals. The activation barrier for oxidation of aliphatic compounds can be decreased at noble-metal electrodes with partially unsaturated d-orbitals (e.g. gold, platinum) that can adsorb and thereby stabilize free radical oxidation products and intermediates. Carbon electrodes are not electrocatalytic and are unsuitable for pulsed amperometric detection. 

Oxidation of Aliphatic Compounds. - In volume terms, the use of Ti02 for the photodegradation, and ultimately photomineralization, of a wide variety of substances continues to dominate this area of photochemistry. Although many of the publications resulting from this work involve the standard application of... 

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