Acetate, active from acetaldehyde

An aryloxypyrimi done has been described as an anti ulcer agent this activity is of note since the agent does not bear any structural relation to better known anti ulcer drugs. Displacement of halogen on the acetal of chloro-acetaldehyde by alkoxide from m-cresol gives the intermediate This affords enaminoaldehyde when subjected... 

The conversion of ethyl alcohol by way of acetaldehyde into acetic acid is the chemical expression equivalent to acetic fermentation. In this process the acetic bacteria utilise atmospheric oxygen in order to bind the hydrogen. That the hydrogen which has to be removed is activated, and not the oxygen (as was formerly thought), is shown by experiments in which oxygen is eaxluded and replaced by quinone the bacteria produce acetic acid from alcohol as before and the quinone is reduced to hydroquinone. 

A very high activity of mitochondrial aldehyde dehydrogenases (together with its low ensures very efficient oxidation in the liver so that the concentration of acetaldehyde in blood remains very low. Nonetheless, it is possible that some of the pathological effects of ethanol are due to acetaldehyde (ethanal). In contrast, a large proportion of the acetate escapes from the liver and is converted to acetyl-CoA by acetyl-CoA synthetase in other tissues ... 

Even with added iodide salt formation of the inactive [Rh(CO)2l4] can be a problem, since under anhydrous conditions this Rh(III) species cannot be reduced to the active [Rh(CO)2l2] by reaction with water. In the Eastman process, this problem is addressed by addition to the CO gas feed of some H2 which can reduce [Rh(CO)2l4] by the reverse of Equation 8. However, the added H2 does lead to some undesired by-products, particularly ethylidene diacetate (1,1-diacetoxyethane) which probably arises from the reaction of acetic anhydride with acetaldehyde (Equation 19 from hydrogenolysis of a rhodium acetyl) ... 

Pt-Sn/C catalysts with 10-20 at. % of Sn exhibited best activity at low potentials. Results from Jiang et al. [68] showed that the ft-SnOx/C catalyst with 30 at.% of Sn was the most active among four different Pt/Sn ratios. An integrated surface science and electrochemistry study of the SnOx/Pt(lll) model catalysts indicate a volcano dependence of the EOR activity on the surface composition, with the maximum at the SnOx coverage of 37 % [69]. Despite the improved overall EOR activity of optimized Pt- n system, on-line differential electrochemical mass spectroscopy (OEMS) studies have shown that acetic acid and acetaldehyde represent the dominant products with CO2 formation contributing only 1-3 % [68]. 

It is postulated that in water, A -vinylpyrrolidone forms a monohydrate. If hydrogen peroxide is added, the medium becomes acidic—presumably because of the formation of acetic acid from the acetaldehyde that is generated from the monomer. For this reason the reaction medium is usually buffered to maintain the pH between 8 and 7. Ammonia or amines, aside from acting as buffering agents, also have an activating effect. 

There is strong evidence that TPP, in functioning as a coenzyme, combines directly with the substrate to form an active intermediate. This may be regarded as a further step in the metabolism of thiamine and the way in which the combination takes place is suggested by the thiamine-catalyzed nonenzymic formation of acetoin and acetic acid from diacetyl and acetaldehyde. It has been shown, by using C -labeled acetaldehyde, that this is not an oxidation-reduction but rather a transfer reaction. 

A strategy to avoid a potentially hazardous release of highly tritiated volatile building blocks is to operate on nonvolatile derivatives from which they can be released as required. This is illustrated for high specific activity acetic acid and acetaldehyde by the catalytic tritiodehalogenation of derivatives 122 (X = Br —> and 123 (X = C1 —>... 

The lower total activity for Rh electrodes may be partly due to increased CO poisoning and slower CO electro-oxidation kinetics compared with Pt electrodes, as demonstrated by the number of voltammetric cycles required to oxidize a saturated CO adlayer from Rh electrodes (see Section 6.2.2) [Housmans et al., 2004]. In addition, it is argued that the barrier to dehydrogenation is higher on Rh than on Pt, leading to a lower overall reaction rate [de Souza et al., 2002]. These effects may also explain the lower product selectivity towards acetaldehyde and acetic acid, which require the dehydrogenation of weakly adsorbed species. 

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