Glyoxal, formation

In this contribution the re-evaluated yields from the OH-radical initiated oxidation of benzene, toluene, p-xylene, and initial results of new simulation chamber experiments on prompt glyoxal formation from isoprene oxidation are presented. A detailed discussion of sources, sinks and their uncertainties to model atmospheric concentrations of glyoxal is presented, and exemplifies how basic research in environmental simulation chambers besides giving input for photochemical models also triggers advancements with measurement techniques for field observations. The integration of laboratory and field observations by models in turn will guide future research on atmospheric chemical processes. 

While the formation of glyoxal from aromatic VOC is likely over-predicted by the MCM code (m part due to the lower re-eva uated glyoxal yields), glyoxal formation is under estimated from alkenes hke d for which glyoxal is not a predicted oxidation product. 

Volkamer, R., U. Platt, and K. Wirtz Primary and Secondary Glyoxal Formation from Aromatics Experimental Evidence for the Bicycloalkyl-Radical Pathway from Benzene, Toluene, and p-Xylene, Journal of Physical Chemistry A, 105 (2001) 7865-7874. 

The breakdown of the carbon skeleton for 2(5H)-furanone (also a photolysis product of butenedial) has been updated and -angelica lactone has been replaced by -angelica lactone to reduce secondary glyoxal formation. These changes were prompted by findings of Volkamer et al. (2001) that secondary glyoxal formation in the toluene system is negligible. 

Copper-based scavengers (formation of insoluble copper sulfide) Iron-oxide-based scavengers (formation of insoluble iron sulfide) Formaldehyde/methanol (formation of water-insoluble, cyclic thio compounds) Glyoxal (formation of thio acetals and other compounds)... 

VoDeamer, R., Platt, U., Wirtz, K. Primary and secondary glyoxal formation from aromatics experimental evidence for the bicycloalkyl — radical pathway from benzene, toluene, and p-xylene. J. Phys. Chem. A 105,7865-7874 (2001)... 

Examples include acetaldehyde, CH CHO paraldehyde, (CH CHO) glyoxal, OCH—CHO and furfural. The reaction is usually kept on the acid side to minimize aldol formation. Furfural resins, however, are prepared with alkaline catalysts because furfural self-condenses under acid conditions to form a gel. 

Many pyrazine and quinoxaline syntheses yield mono- or di-N-oxides (76H(4)769). The condensation of a-aminooximes with 1,2-diketones results in the direct formation of pyrazine mono-N-oxides. The a-aminooximes themselves are not easily prepared but 2-amino-2-deoxy sugars readily form the oximes, which have been condensed with glyoxal to yield the pyrazine 4-oxides (Scheme 18) (72JOC2635, 80JOC1693). 

Oxaziridine syntheses were broadly Investigated from a stereochemical point of view. The formation of two isomeric bis-oxaziridines (249) from glyoxal pointed to a tetrahedral... 

Macrocycles have been prepared by formation of macrocyclic imines as well as by using variations of the Williamson ether synthesis ". Typically, a diamine or dialdehyde is treated with its counterpart to yield the Schiff s base. The saturated macrocycle may then be obtained by simple reduction, using sodium borohydride, for example. The cyclization may be metal-ion templated. In the special case of the all-nitrogen macrd-cycle, 15, the condensation of diamine with glyoxal shown in Eq. (4.14), was unsuccess-ful ... 

Most of the compounds in this class have been prepared from preexisting crown ether units. By far, the most common approach is to use a benzo-substituted crown and an electrophilic condensation polymerization. A patent issued to Takekoshi, Scotia and Webb (General Electric) in 1974 which covered the formation of glyoxal and chloral type copolymers with dibenzo-18-crown-6. The latter were prepared by stirring the crown with an equivalent of chloral in chloroform solution. Boron trifluoride was catalyst in this reaction. The polymer which resulted was obtained in about 95% yield. The reaction is illustrated in Eq. (6.22). 

Treatment of glyoxal with sulfur tetrafluoride in the presence of sodium fluoride results iii the formation of difluoroethylene glycol orthosulfite [174] (equation 89) Similarly, perfluonnated 1,2-diketones react with sulfur tetrafluonde to give tetraoxyspirosulfuranes as the only products Thus, perfluorobiacetyl gives a ciystalhne product, perfluorobutylene glycol 2,3 orthosulfite [175] (equation 89)... 

Diphenyl-1,2,4-triazine 4-oxide 139 was obtained by reaction of diphenyl-glyoxal mono-2-ethoxymethylenehydrazone 140 with hydroxylamine. The reaction proceeds via formation of an isonitroso intermediate, followed by cyclization to the 1,2,4-triazine 4-oxide 139 (71LA12). 

The degradation of 1,2,3-trichloropropane by Agrobacterium radiobacter strain ADI involves hydrolysis of an intermediate epichlorohydrin (3-chloroprop-l-ene) to the diol (Bosma et al. 1999, 2002). An enzyme from this strain has been modified from the use of epichlorohydrin that is its normal substrate to accept dy-l,2-dichloroethene with the release of chloride and the presumptive formation of glyoxal (Rui et al. 2004). 

You and co-workers have demonstrated enantioselective y-lactone formations nsing glyoxalate 163, achieving up to 78% ee with the NHC derived from chiral triazohum salt 164, although with low levels of diastereoselectivity (Scheme 12.35) [70],... 

Polar C=Y double bonds (Y = NR, O, S) with electrophilic carbon have been added to suifinic acids under formation of sulfones. As in the preceding section one must distinguish between carbonyl groups and their derivatives on the one hand, and carboxylic acids (possessing leaving groups at the electrophilic carbon) on the other. Aldehydes " of sufficient reactivity—especially mono-substituted glyoxals - —and their aryl or arylsulfonyl imines have been added to suifinic acids (in a reversible equilibrium) to yield a-hydroxy or a-amino sulfones the latter could also be obtained from the former in the presence of primary amines (equation 26). 

Alternatively, this may be done in a flask, which is shaken by hand frequently to prevent formation of a solid cake. The use of a stirrer results in a granular product. The mother liquor retains about 7 g. of glyoxal bisulfite per liter. 

Exactly this problem was the subject of synthetic experiments carried out by J. Oro et al. (1984), which were intended to clarify the possible formation of these condensation agents. They used simple compounds, such as formaldehyde, acetaldehyde, glyoxal and ammonia as starting materials, and were able to synthesize imidazole as well as its 2- and 4-methyl derivatives. 

Heats of formations (A//f) of the possible two trans- and four cA-fused stereoisomers of the 9-hydroxyperhydropyr-imido[2,1 / 1,4]oxazine 287 derived from 3-(2-hydroxyethyl)-l,3-propanediamine and glyoxal were calculated by the AMI program. Experimentally, 287 was obtained as 3 1 cis—trans mixture the isomers were not separated < 1996H(43)1991 >. 

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