Acetaldehyde, degradation product

The products of the selective electrochemical fluorination of butadiene with platinum electrodes in amine/ HF mixtures, particularly Et,N 3HF, were 3,4-difluorobut-1-cnc and 1,4-difluorobut-2-ene in a ratio of 1 2, 2.3-dimethyIbut-2-enc gave 2.3-difluoro-2,3-dimelhylbutane (yield 22%), while 2-mcthylbut-2-ene gave 2,3-difluoro-2-methyIbutanc (yield 23%) and 2,2-difluoro-3-methylbutane (yield 11 %). Oct-1-ene could not be fluorinated instead, the solvent degraded. Volatile degradation products were acetaldehyde, acetyl fluoride and fluorocthane. 

The synthesis of the (i) 4-hydroxy-6-methoxytetrahydrofuro[2,3-6]-benzofuran ring (116), a degradation product of natural substances of the sterigmatocystin series, is similar,318 as is the synthesis of the dihydro derivative (117) from the o-acetylated acetaldehyde (118), a nonisolated intermediate which is ring-closed to 119 and then heated in toluene to give 117. The last is the starting point for the synthesis of aflatoxin M4 (49).153... 

Abeles and associates showed that when dioldehydratase (Table 16-1) catalyzes the conversion of l,2-[l-3H]propanediol to propionaldehyde, tritium appears in the coenzyme as well as in the final product. When 3H-containing coenzyme is incubated with unlabeled propanediol, the product also contains 3H, which was shown by chemical degradation to be exclusively on C-5 . Synthetic 5 -deoxyadenosyl coenzyme containing 3H in the 5 position transferred 3H to product. Most important, using a mixture of propanediol and ethylene glycol, a small amount of inter-molecular transfer was demonstrated that is, 3H was transferred into acetaldehyde, the product of dehydration of ethylene glycol. Similar results were also obtained with ethanolamine ammonia-lyase 399... 

Red 2 exposed to different sugar degradation products at 100 °C gave the following %A values (min) glyceraldehyde, 20 glycolaldehyde, 30 triose reductone, 40, dihydroxyacetone, 50 2-oxopropanoic acid, 60 3-hydroxy-2-butanone, 90 butane-dione, 300 HMF, 450 2-oxopropanal, 1200 acetaldehyde, acrolein, and laevulinic acid, no reaction. 

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). 

Chlorinated phenols are common environmental pollutants, introduced as pesticides and herbicides. Studies have been carried out on the potential use of radiation to destroy these compounds as a means of environmental cleanup . While these studies were concerned with mechanisms (and are discussed in the chapter on transient phenoxyl radicals), other studies involved large-scale irradiation to demonstrate the decomposition of phenol in polluted water . Continuous irradiation led to conversion of phenol into various degradation products (formaldehyde, acetaldehyde, glyoxal, formic acid) and then to decomposition of these products. At high phenol concentrations, however, polymeric products were also formed. 

In a couple of studies, SPME methods were developed to follow the migration of low molecular weight compounds from bottles for mineral water. Acetaldehyde is a common degradation product of poly(ethylene terephtha-late) formed during the melt condensation reaction and melt processing of PET. A rapid and sensitive SPME method was developed to extract acetaldehyde by inserting the carbowax/divinylbenzene fiber into the inner air-space of PET bottles [81]. The detection limit was 0.5 mLL and relative standard deviation was lower than 7%. The acetaldehyde content of 50 PET bottles was analysed. In another study, the SPME method was developed to determine the terephthalic acid monomer from aqueous solutions [43]. 

The MCM v3 butane degradation chemistry has been evaluated using chamber data on the photo-oxidation of butane, and on photo-oxidation of its degradation products, methylethyl ketone (MEK), acetaldehyde (CH3CHO) and formaldehyde (HCHO), in conjunction with an initial evaluation of the chamber-dependent auxiliary mechanisms for the series of relevant chambers. 

The synthesis described by Sulser et al. (1972) starts by condensation of diethyl oxalate with ethyl propanoate, which is followed by condensation with acetaldehyde and acidic decarboxylation. Martin et al. (1990) used this synthesis but with aqueous thermal decarboxylation, the sample thus obtained proved to be stable (three years in a freezer). They studied the equilibrium between the enolic sotolone and the ketolactonic form. The enol was unstable at high pH values and the transformation was irreversible by lowering the pH. Only the enol was observed in UV and NMR spectra. Moreover the degradation by UV light led the authors to suspect the intervention of a UV-induced radical. One of the degradation product was l-penten-3-ol (B.30). Both the enantiomers have been synthesized by Okada et al. (1983) from the enantiomers of tartaric acid. 

Using labeled precursors, Blank et al. (1996) explained the formation of homofuraneol in reactions of xylose with alanine (preferentially to glycine). The proposed mechanism suggested the incorporation of the Strecker degradation product, acetaldehyde. This mode of formation is preferred to sugar fragmentation. 

Its formation during roasting is probably due to the reaction of ammonia on 2,3-hexanedione and acetaldehyde, the Strecker degradation product of alanine. 

Heating sucrose to 300°C in a stream of nitrogen produces volatile furan compounds namely 2-methyl furan, furan, 2-hydroxyacetyl furan, and other volatile reaction products (methanol, acetone, acrolein, propanol, and acetaldehyde) [230]. A major compound (2-furfural) and volatile thermal degradation products (2-furyl methyl ketone, 2-furyl propyl ketone, methyl-benzo( )furan, and 5-methyl-3-hydro-furan-2-one) were identified by heating sucrose in an open evaporation dish at 180°C for 90 min [233]. 

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