Benzaldehydes from oxidation

For cinnamic acid at 9.6 °C, a = 0.107, b = 1.25 and k = 0.69 l.mole .sec E = 26.7 0.5 kcal.mole" and AS = 34.5 eu. Identification of products of oxidation of a number of acids indicates two concurrent mechanisms. Predominating is direct attack on the double bond to give, ultimately, cleavage products, e.g. benzaldehyde from cinnamic acid (some phenylacetaldehyde is also found, indicating oxidative decarboxylation to occur) and also acetophenone from 3-phenylcrotonic acid. 

By this procedure the benzaldehyde is oxidized to benzoic acid, which is easily removed from the products. 

Salts of transition metals are widely used in technological processes for the preparation of various oxygen-containing compounds from hydrocarbon raw materials. The principal mechanism of acceleration of RH oxidation by dioxygen in the presence of salts of heavy metals was discovered by Bawn [46 19] for benzaldehyde oxidation (see Chapter 1). Benzaldehyde was oxidized with dioxygen in a solution of acetic acid, with cobalt acetate as the catalyst. The oxidation rate was found to be [50] ... 

It is now generally admitted that this reaction involves both one-electron and two-electron transfer reactions. Carbonyl compounds are directly produced from the two-electron oxidation of alcohols by both Crvl- and Crv-oxo species, respectively transformed into CrIV and Crm species. Chromium(IV) species generate radicals by one-electron oxidation of alcohols and are responsible for the formation of cleavage by-products, e.g. benzyl alcohol and benzaldehyde from the oxidation of 1,2-diphenyl ethanol.294,295 The key step for carbonyl compound formation is the decomposition of the chromate ester resulting from the reaction of the alcohol with the Crvl-oxo reagent (equation 97).296... 

It is noticeable that in the oxidation of toluene under oxygen (Fig. 5) o-, m-, and p-cresols resulting from nuclear hydroxylation of the substrate are produced in very low yields in the absence of water, but tend to increase with increasing concentration of water on the contrary, benzaldehyde and benzyl alcohol arising from oxidation of the side chain are produced in much higher yields than cresols in the absence of water, but their yields do not vary with water concentration. 

The solid-state oxidation of a freeze-dried cyclic hexapeptide was examined by Dubost et al. (36). The degradation product was identified as a benzaldehyde derivative resulting from oxidative deamidation of an... 

Some years ago, Schaap and co-workers developed a method by which compounds that do not quench the fluorescence of the singlet excited DCA sensitizer may nevertheless be rapidly oxidized [102, 108, 109, 160-162]. For example, epoxides 69a-d, unreactive under standard DCA-sensitized conditions [107,163], can be readily converted into the corresponding ozonides 70a-c, in high yields, by use of a non-light-absorbing aromatic hydrocarbon, i.e., biphenyl (BP) as a cosensitizer in conjunction with DCA. Variable amounts of carbonyl compounds, such as benzophenone from 69 a, b, benzaldehyde from 69 b, c, d are... 

Alkaline hydrolysis of lignin increases the number of reactive benzylic hydroxyl groups and may also be important in further depolymerizing the lignin once the oxidative-cleavage reaction has occurred. The formation of a p-electron-withdrawing -CHO substituent on aryl lignin units should increase the rate of hydrolysis of the ether bonds (26). Hydrolysis also forms p-phenylate ions, which then protect the benzaldehyde from further reaction via the Cannizzaro reaction, as mentioned earlier. 

Various aldehydes are encountered in wine. The most abundant is acetaldehyde which is both a product of yeast metabolism and an oxidation product of ethanol. Glyoxylic acid, resulting from oxidation of tartaric acid, especially catalyzed by metal ions (Fe, Cu) or ascorbic acid, can also be present. Other aldehydes reported to participate in these reactions include furfural and 5-hydroxymethylfurfural that are degradation products of sugar and can be extracted from barrels (Es-Safi et al. 2000), vanillin which also results from oak toasting, isovaleraldehyde, benzaldehyde, pro-pionaldehyde, isobutyraldehyde, formaldehyde and 2-methylbutyraldehyde which are present in the spirits used to produce fortified wines (Pissara et al. 2003). 

Benzaldehyde is prepared by the hydrolysis of (dichloromethyl)benzene (benzal chloride) in either aqueous acid or aqueous alkali and by the oxidation of toluene with chromium trioxide in acetic anhydride (Scheme 6.3). In the latter synthesis, as the benzaldehyde is formed, it is converted into its diacetate by the acetic anhydride, so preventing further oxidation subsequent hydrolysis generates the aldehyde group. The benzaldehyde has thus been protected from oxidation. Benzyl alcohol can... 

One way of avoiding an extensive anodic degradation of organic compounds is to use acetone as a modifying medium, which is also well known from chemical oxidations, as with KMn04. Benzoin [33] is thus, in sulfuric acid-acetone containing some water cleaved mainly to benzaldehyde (35%) and benzoic acid (45%) a small amount of benzil (5%) and tar (10%) is also formed. Benzil is apparently not an intermediate, as only benzoic acid (67%) was obtained from oxidation of benzil under similar conditions [33] ... 

Lindgren, B. O., Nilsson, T. Preparation of carboxylic acids from aldehydes (including hydroxylated benzaldehydes) by oxidation with chlorite. Acta Chemica Scandinavica (1947-1973) 1973, 27, 888-890. 

Traditionally m-phenoxy benzaldehyde is manufactured from benzaldehyde via bromination, and phenol. However, synthesis of this important agrochemical intermediate from meto-cresol via meto-phenoxy toluene oxidation has now become commercially more attractive. Sumitomo Chemicals, Japan has an excellent technology for making meta-phenoxy benzaldehyde from m-cresol as follows ... 

In order to overcome certain difficulties such as the dissipation of heat and the use of inflammable mixtures, certain liquid phase processes have been proposed for the oxidation of aromatic hydrocarbons and compounds. In such a process 100 the aromatic hydrocarbons or their halogenated derivatives are treated with air or gas containing free molecular oxygen in the liquid phase at temperatures above ISO0 C. and under pressure in the presence of a substantial quantity of liquid water. A small quantity of such oxidation catalysts as oxides or hydroxides of copper, nickel, cobalt, iron or oxides of manganese, cerium, osmium, uranium, vanadium, chromium and zinc is used. The formation of benzaldehyde from toluene is claimed for the process. 

Because of the high vapor pressures of the products obtained in the oxidation, an efficient cooling and collecting system is essential. For this purpose coil condensers followed by scrubbers to vemove unreacted toluene and the lighter products have been used. Thiosulfite solutions may be used in scrubbers to remove the benzaldehyde from the reaction mixture and it has been proposed to use activated charcoal scrubbers after the thiosulfite scrubbers to remove unreacted toluene from the non-condensible gases. 

Selectivity of multiphase reactions catalysed by phase transfer catalysts can be greatly improved by the use of the so called capsule membrane - PTC (CM-PTC) technique. We report here the theoretical and experimental analysis of the CM-PTC and Inverse CM-PTC for exclusively selective formation of benzyl alcohol and benzaldehyde from the alkaline hydrolysis and oxidation of benzyl chloride, respectively. The theoretical analysis shows that it is possible to simultaneously measure rate constant and equilibrium constant under certain conditions. The effects of speed of agitation, catalyst concentration, substrate concentration, nature of catalyst cation, membrane structure, nucleophile concentration, surface area for mass transfer and temperature on the rate of reaction are discussed. 

Benzaldehyde is oxidized when exposed to the air, the reaction taking place more rapidly in the presence of sunlight. It has been shown that the first product formed is benzoyl hydrogen peroxide, which results from the direct addition of one molecule of the aldehyde and one molecule of oxygen —... 

An oxidizing reagent based on potassium ferrate(Vl) has been described [78], This potassium ferrate, when used in conjunction with an appropriate heterogeneous catalyst such as KIO montmorillonite clay, is a strong oxidant which produces cycloalkanols and cycloaUcanones from cycloalkanes, and benzyl alcohol and benzaldehyde from toluene. 

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