Esters aldehyde oxidation

Nitrile Copolymer butadiene-acrylonitrile (NRB) Perfectly suited for lipophilic compounds (aliphatic and aromatic hydrocarbons) WeU-known low resistance to ketones, strong acids, esters, aldehydes, oxidizers, and halogenated products (including fluorinated compounds). Relative rigidity of the thick material... 

Reactions and Uses. The common reactions that a-hydroxy acids undergo such as self- or bimolecular esterification to oligomers or cycHc esters, hydrogenation, oxidation, etc, have been discussed in connection with lactic and hydroxyacetic acid. A reaction that is of value for the synthesis of higher aldehydes is decarbonylation under boiling sulfuric acid with loss of water. Since one carbon atom is lost in the process, the series of reactions may be used for stepwise degradation of a carbon chain. 

The zinc oxide component of the catalyst serves to maintain the activity and surface area of the copper sites, and additionally helps to reduce light ends by-product formation. Selectivity is better than 99%, with typical impurities being ethers, esters, aldehydes, ketones, higher alcohols, and waxes. The alumina portion of the catalyst primarily serves as a support. 

Hiese unsaturated esters, hy oxidation, permit of the elimination of the CHO group and the preparation of aldehydes or acids with fewer oarbon atoms. 

Methylthiomethyl p-tolyl sulfone 257 was shown to react with various esters in the presence of excess NaH, affording compounds 263 which, upon reduction with NaBH and further treatment with alkali, can be converted to the corresponding aldehydes ". Oxidation of 263 with hydrogen peroxide gives S-methyl a-ketocarbothioates 264. ... 

In an attempt to use an acyl anion equivalent to open an aziridine, Wu and co-workers isolated an unexpected ring opened product 316 (Eq. 31) [158], The authors found that the presence of oxygen was the determining factor between benzoin formation and ester formation. No desired ketones were ever formed. Various aromatic substituted aldehydes were treated under standard reaction conditions to afford esters in good yields. 4-Methoxybenzaldehyde provided product in only 40% yield, presumably due to the ease of aldehyde oxidation. 

Kinetic studies were made on the cleavage of franx-cinnamate to benzoic acid by stoich. [Ru0 p7aq. 1.7M NaOH/85°C isotope effects and activation parameters were determined. Formation of an alkene-[RuO ] cyclic Ru(lV) ester (1), oxidation of this with more ruthenate to the cyclic Ru(Vl) ester (2) and oxidative decomposition of this via (3) to aldehydes R CHO and R CHO was suggested. The aldehydes are subsequently oxidised to R COOH and R COOH by more [RuO ] (not shown in the Scheme) (Fig. 1.16) [349, 350],... 

The reactivity of acidified chlorite solutions is reduced for bleaching some textiles by adding compounds like polyamines, pyrophosphates, and hydrogen peroxide that suppress the formation of chlorine dioxide (57). Another method is to buffer the solution at pH 5—6 to reduce the rate of chlorine dioxide formation. Hydrolysis of anhydrides and esters or oxidation of alcohols can be used to slowly generate acids to promote chlorine dioxide formation (58). Aldehydes also promote chlorine dioxide generation from neutral chlorite solutions, but the effect is greater than simply lowering the pH as they... 

Acids Alcohols Aldehydes Esters Ketones Oxides Terpenes... 

Addition of H and CO to alkenes and alkynes catalysed by transition metal complexes is called hydrocarbonylation, and is useful for the syntheses of carboxylic acids, their esters, aldehydes and ketones [1]. Oxidative carbonylation of alkenes and alkynes with Pd(II), treated in Section 11.1.5, differs mechanistically from hydrocarbonylation. Some carbonylation reactions occur at under 1 atm or low pressures, without using a high-pressure laboratory apparatus. Several commercial processes based on hydrocarbonylation have been developed. 

The aluminum alkoxide mixture or "oxidized growth product is fed to a series of vacuum flash evaporators to remove solvent introduced earlier in the triethylaluminum preparation. This vacuum stripping step also removes olefins formed during the growth reaction and the myriad of by-products formed during oxidation (14) Efficiency of this stripping process is a key factor in alcohol product quality. This is the opportunity to separate volatile impurities—olefins, esters, aldehydes, paraffins, etc.—from product alcohols while the alcohols are in a nonvolatile form (aluminum alkoxides). 

Protection of 194 as a p-methoxybenzylether and subsequent epoxydation led to the trans-epoxide 195, which was transformed into the unsaturated aldehyde 196 by a three-reaction sequence, including regioselective oxirane opening with a 1,3-dithiane anion, hydrolysis of the dithioacetal formed, and dehydration. Chlorite promoted aldehyde oxidation, methyl ester formation, and removal of the hydroxyl protections delivered methyl (+)-shikimate 197 in a remarkable 12% yield from 193. 

The sp2 C-H bond of aldehydes, formamides, or formate esters undergoes oxidative addition to ruthenium complexes to generate acylruthenium hydride, which can insert alkenes leading to the overall H-COR addition to alkenes [122] (Eq. 91). 

The effective oxidant in the TPAP oxidation of alcohols is the perrathenate ion, a Ru(VII) compound. This compound is employed in catalytic amounts only but is continuously replenished (see below). The mechanism of the alcohol —> aldehyde oxidation with TPAP presumably corresponds to the nonradical pathway of the same oxidation with Cr(VI) (Figure 14.10, top). Accordingly, the key step of the TPAP oxidation is a /3-elimination of the ruthenium(VII) acid ester B. The metal is reduced in the process to ruthenium(V) acid. 

In the two-step process, the second-stage reactor is similar to the first-stage reactor but is packed with an optimized catalyst for aldehyde oxidation, based on Mo V oxides, and is run under different operating conditions. Care must be exercised during the separation and purification phases to avoid conditions favouring acrylic acid polymerization, e.g., by addition of a radical polymerization inhibitor such as the hydroquinone monomethyl ether. Selectivities to acrylic acid are higher than 90% at total conversion of the aldehyde. Overall yields referred to propylene are in the range 75-85%. Most acrylic acid produced is esterified for the production of acrylate esters. 

Primary and secondary allylic alcohols and saturated secondary alcohols are oxidized to the corresponding carbonyl compounds quickly and in high yield at room temperature in DMF. There is no appreciable overoxidation of allylic alcohols in DMF, but primary saturated alcohols are readily oxidized to their corresponding acids. Recently, it has been reported that aldehydes may be converted to methyl esters by oxidation with PDC in the presence of methanol. Preparation of other esters, or methyl esters direct from the alcohol, proved to be less efficient. 

Tischchenko-type dimerization of aldehyde is catalyzed by dihydridorutheni-um(II) complexes. In this reaction, aldehyde is initially consumed to reduce Ru(II) to give Ru(0), to which aldehyde oxidatively adds to give a hydrido(acyl)mtheni-um(II) active intermediate affording esters [15]. Hydroacylation of olefins [16] and dienes [17] is also catalyzed by ruthenium complexes (Scheme 14.5). 

Although Smh is more chemoselective than traditional dissolving metal reagents, it does react with sulfoxides, epoxides, the conjugated double bonds of unsaturated ketones, aldehydes and esters, alkyl bromides, iodides and p-toluenesulfonates. It does not, however, reduce carboxylic acids, esters, phosphine oxides or alkyl chlorides. In common with most dissolving metal systems, ketones with an a-hetero substituent suffer loss of the substituent rather than reduction of the carbonyl group. ... 

In addition to the ozonolysis of alkenes and a few aromatic compounds [93, 104], ozone oxidizes other groups. Thus saturated hydrocarbons containing tertiary hydrogen atoms are converted into tertiary alcohols [105, 106], and some alkenes are transformed into epoxides [107] or a,p-unsat-urated ketones [108], Benzene rings are oxidized to carboxylic groups [109, ethers [110] and aldehyde acetals [111] to esters aldehydes to peroxy acids [772] sulfides to sulfoxides and sulfones [775] phosphines and phosphites to phosphine oxides and phosphates, respectively [775] and organomer-cury compounds to ketones or carboxylic acids [114]. 

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