Acetaldehyde mechanism

Vinyl acetate is formed by a 6-elimination of a hydridopalladium moiety (Structure 3), which was the first step of the hydride shift in the acetaldehyde mechanism (eq. (12)) (Section 2.4.1). 

Apart from a small seeondary influence of the changes in the HCHO photolysis parameters, no further modifications were required to the acetaldehyde mechanism. As shown in Figure 4 to Figure 7, MCM v3a provides a very good description of D(03-NO) in the complete set of CH3CHO-NOX chamber experiments. 

Studies of the reaction mechanism of the catalytic oxidation suggest that a tit-hydroxyethylene—palladium 7t-complex is formed initially, followed by an intramolecular exchange of hydrogen and palladium to give a i yW-hydtoxyethylpalladium species that leads to acetaldehyde and metallic palladium (88-90). 

The theoretical explanation of the butane reaction mechanism is as fully developed as is that of acetaldehyde oxidation (51). The theory of the naphtha oxidation reaction is more troublesome, however, and less well understood. This is largely because of a back-biting reaction which leads to cycHc products (52). 

Facial dushing after ingestion of alcohol occurs in up to one-third of patients taking chlorpropamide. The mechanism, like that of the disulfiram reaction, probably involves inhibition of the oxidation of acetaldehyde, a metaboUte of ethanol. The plasma concentration of chlorpropamide may be correlated with chlorpropamide—alcohol dushing. 

Acetaldehyde. Acetaldehyde [75-07-0], has a slightly different reaction mechanism with hemoglobin (58). Although this reagent reacts... 

Homogeneous Oxidation Catalysts. Cobalt(II) carboxylates, such as the oleate, acetate, and naphthenate, are used in the Hquid-phase oxidations of -xylene to terephthaUc acid, cyclohexane to adipic acid, acetaldehyde (qv) to acetic acid, and cumene (qv) to cumene hydroperoxide. These reactions each involve a free-radical mechanism that for the cyclohexane oxidation can be written as... 

A. ot-Chloroelhyl ethyl ether. A mixture of 200 g. (201 ml.) of redistilled paraldehyde, b.p. 121-122.5° (equivalent to 4.54 moles of acetaldehyde), and 200 g. (254 ml., 4.34 moles) of absolute ethanol is placed in a 1-1. three-necked flask fitted with a mechanical stirrer and a gas inlet tube reaching to the bottom of the flask. The mixture is cooled to —5° in a mixture of Dry Ice and acetone, and dry hydrogen chloride (Note 1) is passed into the stirred reaction mixture maintained at about —5° until 200 g. (5.48 moles) has been absorbed. During this operation, which requires about 2 hours, the reaction mixture separates into two layers. The upper layer of crude a-chloroethyl ethyl ether is re-... 

It is also possible to carry out the aldol condensation under acidic conditions. The reactive nucleophile is then the enol. The mechanism, as established in detail for acetaldehyde, involves nucleophilic attack of the enol on the protonated aldehyde. 

The following mechanism has been postulated for the gas phase decomposition of acetaldehyde ... 

A reagent more reactive than tris(dimethylamino)arsine employed by Weingarten and White 39) was tetrakis(dimethylamino)titanium (145). With this compound it was possible to prepare N,N-dimethyl(l-isopropyl-2-methylpropcnyl)amine (147) from diisopropyl ketone. Weingarten and White 39) have suggested a possible mechanism for this reaction (see p. 88). If benzaldehyde 39,111), formaldehyde 111), or acetaldehyde 39) is used, the corresponding gem diamine or aminal (143) is formed. 

Paraldehyde, a sedative and hypnotic agent, is prepared by treatment of acetaldehyde with an acidic catalyst. Propose a mechanism for the reaction. 

Due to the high reaction temperatures required during the last stages of these syntheses, side reactions cannot be avoided. Acetaldehyde, carboxyl endgroups, and vinyl endgroups are formed during PET and PEN synthesis. The formation of 2,2/-oxydiethylene moieties in polymer chains by etherification of hydroxyl endgroups is also a well-known side reaction of EG polyester syntheses.264 These reactions should be carefully controlled since they can exert an important influence on polymer properties such as Ts, mechanical properties, hydrolytic stability, and discoloration. 

Condensation of 2-aminothiophenol with the /3-chlorocinnamaldehyde in the presence ofp-toluene sulfonic acid (PISA) gave good yield of benzothia-zole (Scheme 14). The mechanism suggested in this work is beUeved to proceed via a nucleophilic attack of the sulfur atom in an addition-ehmination sequence followed by a spontaneous cyclization and ejection of acetaldehyde [15]. These investigations were performed in a domestic microwave reactor and need 1.5 min for completion (65% yield). Here again, oil bath heating seems to be inferior, providing a maximum conversion of 53% after... 

This mechanism accounts for the fact, established by deuterium labeling, that the four hydrogens of the acetaldehyde all come from the original ethylene and none from the solvent. 

Ethanol is oxidized by alcohol dehydrogenase (in the presence of nicotinamide adenine dinucleotide [NAD]) or the microsomal ethanol oxidizing system (MEOS) (in the presence of reduced nicotinamide adenine dinucleotide phosphate [NADPH]). Acetaldehyde, the first product in ethanol oxidation, is metabolized to acetic acid by aldehyde dehydrogenase in the presence of NAD. Acetic acid is broken down through the citric acid cycle to carbon dioxide (CO2) and water (H2O). Impairment of the metabolism of acetaldehyde to acetic acid is the major mechanism of action of disulfiram for the treatment of alcoholism. 

This agrees with experimental findings on the decomposition of acetaldehyde. The appearance of the three-halves power is a wondrous result of the quasisteady hypothesis. Half-integer kinetics are typical of free-radical systems. Example 2.6 describes a free-radical reaction with an apparent order of one-half, one, or three-halves depending on the termination mechanism. 

Solution The procedure is the same as in the acetaldehyde example. ODEs are written for each of the free-radical species, and their time derivatives are set to zero. The resulting algebraic equations are then solved for the free-radical concentrations. These values are substituted into the ODE governing RCl production. Depending on which termination mechanism is assumed, the solutions are... 

Reduction of vinyl radicals by to the corresponding anion also has been observed (216). When purified acetylene is bubbled through Fenton s reagent, acetaldehyde is formed as a product, presumably via the following mechanism ... 

No example of intramolecular displacement to give Co(I) has yet been reported. /3-Hydroxyethyl complexes are decomposed by alkali to give Co(I) and acetaldehyde, and it has been suggested (33) that this might proceed via the intermediate formation of the epoxide. But the results are more easily explained on the basis of the established mechanism involving the cis elimination of Co—H (see Section f). 

The present research was focused on the study of acetaldehyde oxidation rising air with aqueous mangan acetate catalyst in mechanically stirred tank reactor. 

Reactions without wells can also exhibit multiple pathways due to deviation from the MEP. While many trajectories may follow the MEP over a saddle point, alternative pathways arise when forces on the PES steer away from the saddle point, typically into relatively flat regions of the PES, before finding an additional path to the same exit channel. The roaming mechanisms recently elucidated in the photodissociation of formaldehyde and acetaldehyde, and the reaction of CH3 + O, are examples of this phenomenon, and are discussed in Section V. 

For n-alkanes, n-alcohols, 1-chloroalkanes, n-ethers, and chloroethenes, the carbon chain length influences the reactivity, and the clear linear correlations indicate that the attack mechanism of these pollutants by OH or Cl radicals occurs via the same pathway. However, such correlations do not hold true for aromatics, ketones, and aldehydes, for reasons discussed in our previous paper [3]. We also estimated missing values of kci by analogy for ethylbenzene, we take kci = 1.5e-10 cm molecule S, greater than that for m-xylene, but smaller than the 2.0e-10 cm molecule- s-i value for very reactive compoxmds. Also we estimate a similar value for butyraldehyde kci = le-10 cm molecule- s-, only 10% larger than kci of acetaldehyde to remain consistent with the equivalent koH value. 

Alcohol abuse is a major clinical problem in many countries and has been the subject of investigation for many years by those interested in determining the molecular basis of ethanol-induced liver dam e (see Lieber, 1990). These intensive and extended efforts have revealed much about the metabolism of ethanol in the liver and about the toxicity of its primary oxidative product, acetaldehyde. They have not, however, folly elucidated the molecular mechanisms that lead to the typical features of alcoholic liver injury steatosis, necrosis and eventually cirrhosis. 

Lai SCS, Kleyn SEF, Rosea V, Koper MTM. 2008. Mechanism of the dissociation and electro-oxidation of ethanol and acetaldehyde on platinum as studied by SERS. J Phys Chem C 112 19080-19087. 

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