Alkane from aldehydes

The complex 8, formed by the addition of 2-propenylmagnesium chloride to 7, adds to aromatic aldehydes, 1-alkanals, a-branched and unbranched alkanals uniformly from the 7 c-face leading to hoinoallylic alcohols with 88-94% ee35 (Method A). After hydrolytic workup, both components can be recycled. Allyl complexes 10, generated from 9, prefer 67-attack and lead to the ent-homoallylic alcohols with excellent enantioselectivity36 (Method B) (Table 8). 

Both the modeling studies and smog-chamber simulations show significant oxidant formation with NO -h aldehydes, NO, + alkanes (except methane), or even NO, -i- carbon monoxide in moist air. The development of significant oxidant from NO + aldehydes is particularly ominous, because aldehyde emission is not now controlled. As the modelers state [Pg.27]

Small alkylperoxy and alkoxy radicals can decompose uni-molecularly, though their rate constants are often in the second-order region. They abstract hydrogen atoms from alkanes, aldehydes, esters, and acids, add to olefins, and may react with 02. Furthermore, interactions with other radicals can lead to disproportionation or combination. These reactions are reviewed, and particular attention is given to CH 02 and CH30 a number of rate constants are estimated. 

The mechanism of reductive elimination of a hydrido alkyl complex is therefore often approached in an indirect manner. The hydrido-alkyl complex is made not by oxidative addition of the alkane but by some other route. The decomposition of the hydrido-alkyl complex to give alkane is then studied for mechanistic information. Reductive eliminations of an aldehyde from an acyl-hydrido complex, Reaction 2.7, and acetyl iodide from an iodo-acyl complex,... 

Titanosilicalite (TS-1)[165,166], a highly siliceous MFI type zeolite in which 0.1 to 2.5% of the Si atoms are replaced by Ti, is the most successful example for the use of isomorphously substitited zeolites. As a consequence of the high Si/Al ratio of TS-1 the material contains only a negligible concentration of strong Bronsted acid sites. In fact, the presence of acid sites is detrimental to the selectivity of the catalysts, as discussed below. TS-1 has been found to be a selective oxidation catalyst for a wide variety of reactions such as the conversion of alkenes to epoxides [167], alcohols to aldehydes [168], alkanes to secondary alcohols and ketones [169,170], phenol to hydroquinone and catechol [171] and amines to hydroxylamines [ 172]. A schematic representation of the chemistry is given in Fig. 7 which is adapted from ref [17]. 

The role of free-radical intermediates in one-electron reactions has been studied over many decades and characterized in a large number of chemical transformations. It has only been since the mid-1980s that interest in free- radical reactions has increased in the context of functionalization of organic molecules. The incorporation of CO in organic molecules via free-radical reactions was another clever method for the formation of lactones, acids, and aldehydes starting from alkanes (Scheme 5). 

Determination of the residual antioxidant content in polymers by HPLC and MAE is one way to determine the amoimt needed for reasonable stabilization of a material, and also to compare different antioxidants and their individual efficiencies. During ageing and oxidation of PE, carboxyhc acids, dicarboxylic acids, alcohols, ketones, aldehydes, n-alkanes and 1-alkenes are formed [86-89]. The carboxyhc acids are formed as a result of various reactions of alkoxy or peroxy radicals [90]. The oxidation of polyolefins is generally monitored by various analytical techniques. GC-MS analysis in combination with a selective extraction method is used to determine degradation products in plastics. ETIR enables the increase in carbonyls on a polymer chain, from carboxylic acids, dicarboxyhc acids, aldehydes, and ketones, to be monitored. It is regarded as one of the most definite spectroscopic methods for the quantification and identification of oxidation in materials, and it is used to quantify the oxidation of polymers [91-95]. Mechanical testing is a way to determine properties such as strength, stiffness and strain at break of polymeric materials. 

One main characteristics of n-butane oxidation is the substantial absence of by-products of partial oxidation other than maleic anhydride (apart from a low amount of phthalic anhydride). This means that once the alkane has been adsorbed and transformed to the first intermediate species, the latter has to be quickly transformed up to the final stable product. If this requirement is not met, the adsorbed olefinic-like intermediate may desorb. This leads to a lower selectivity to the final desired product, because the olefin may be readsorbed on nonspecific oxidizing sites yielding other undesired products (aldehydes or acids), which can also be precursors for the formation of carbon oxides. Therefore, a rapid transformation of the adsorbed intermediates to oxidized products is necessary in order to obtain high selectivity to the desired product. In order to guarantee this selective pathway, the catalyst surface must provide the required arrangement of specific oxidizing sites the different functional properties must be arranged so as to provide an ensemble of sites (or, alternatively, sites with multifunctional properties) able to allow the reaction pathway from alkane adsorption and activation up to its transformation to the final product to be completed. 

Captodative alkenes 67 can be dialkylated, for example, by addition of iso-butyronitrile radical derived from thermal decomposition of AIBN under the same conditions as those which lead to polymerization of other acrylic alkenes. For example, a-morpholino-acrylonitrile (67, c = CN, d = N(CH2CH2)20) leads to 69, in 71% yield (Scheme 12) [4a]. With a-/-butylthio-acrylonitrile (67, c = CN, d = SC(CHj)3), the same process leads to 70 in 88% yield [7]. The adduct radical 68 is highly stabilized, and is in equilibrium with dimer 70. The reaction is quite general, and has been applied to other captodative alkenes (c = CN, COR, CO2R and d = NR2, OR, SR) together with various sorts of radical partners, derived from alkanes, alcohols, thiols, thioethers, amines, amides, ketones, aldehydes, acetals and thioacetals [44, 45]. 

Functional alkanes bearing a 2,3-dihydroxylated pattern are readily obtained, for example, aldehydes from l-acetoxy-2-alkenyl phenyl sulfones and esters from ketene acetals. ... 

We obtain the systematic name for an aldehyde from the parent alkane by removing the final -e and adding -al. For ketones the final -e is replaced by -one, and a number indicates the position of the carbonyl group where necessary. The carbon chain in ketones is numbered such that the... 

Carbonylation. Homologous aldehydes are formed as the major products from alkanes under radical carbonylation conditions. Thus, magnetically stirred acetonitrile solutions of Bu N CWjpOjj) or Bu, N (PW,204q) and alkanes are saturated with CO (1 atm) and are irradiated (550-W medium-pressure Hg lamp and a Pyrex filter) at room temperature for 16 hours to complete the reaction. 

The oxidation of unsaturated aldehydes provides an important source of additional aldehydes from the decomposition of hydroperoxides. The oxidation products of 2-nonenal include alkanals, glyoxal, and mixtures of a-keto aldehydes. The same products are formed from the oxidation of 2,4-heptadienal,... 

Du et al. (50-52) reported no differences in TBARS between irradiated and nonirradiated chicken breast fillets and chicken and turkey rolls. As dietary CLA increased, however, the TBARS values of chicken rolls decreased. This could be caused by the decreased unsaturated fatty acid content in meat after dietary CLA treatment (53). We have observed similar results in vacuum-packaged irradiated meats in that ready-to-eat (RTE) turkey rolls from birds fed CLA treatment had lower TBARS than did those fed the control diet. The main reason for the improved oxidative stability could be due to the decreased proportion of unsaturated fatty acids in meat caused by the dietary CLA (54). Irradiation had a significant influence on numerous volatiles, mainly sulfur compounds, aldehydes, and alkanes. Dimethyl sul-... 

Wax analysis on the surface of the leek leaf revealed that a C31 ketone was a major component in the wax demonstrating that the decarbonylation pathway was dominant in the leek. The C31 ketone, therefore, was used as a marker to monitor wax content in subsequent experiments. Other detectable components included aldehydes and alkanes with chain length ranging from C26 to C31 as well as free fatty acids from Cl6 to C22. The analyses also showed that there was a differential accumulation of the total wax along the length of the leaf (Fig. 1). The lower section of the leaf has little wax compared to the upper portions of the leaf. Increased wax accumulation began in segment III (Fig. 1) and continued until... 

Indirect oxidation of propylene is an important route for propylene oxide production that proceeds in two reaction steps. The first step is the formation of a peroxide from alkanes, aldehydes, or adds by oxidation with air or oxygen. The second reaction step is the epoxidation of propylene to PO by oxygen transfer from the peroxide with formation of water, alcohol, or acid. The catalytic oxidation of propylene with organic hydroperoxides is nowadays a successful commercial production route (51% of world capacity). Two organic hydroperoxides dominate the processes (i) a process using isobutane (peroxide tert-butyl hydroperoxide, co-product tert-butyl alcohol), which accounts for 15% of the world capacity and (ii) a process using ethylbenzene (peroxide ethylbenzene hydroperoxide, co-product styrene) that accounts for 33% of the world capacity. The process via isobutane is presented by ... 

However, less is know about the quantitative details of these processes than is the case for the alkanes. In general, unimolecular decomposition of the alkoxy radicals [e.g., CH3CH20CH(0 )CH3 in the above reaction sequence] is more rapid than for an alkane-derived radical of similar structure. The major end product of ether oxidation is quite often an ester, the analog to the carbonyl compounds (aldehydes and ketones) generated from alkane oxidation. 

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