Oxalic acid, first analysis

CoASH for 15 minutes. Labeled microsomes were separated into equal aliquots for assays. Assay reactions contained ImM reduced dinucleotide and were allowed to proceed 1-3 h prior to terminating by extracting with 2 vol chloroform methanol (2 1) and addition of a few drops of 1 M oxalic acid. Chlorofom extracts were blown to dryness with N2 and lipids were methylated by first adding 0.5 ml sodium methoxide (18 mg/ml) in methanol for 30 min and then adding ethereal diazomethane. In order to ensure complete recovery of lipids, methyl esters were extracted with 2 vol of chloroform water was added for phase separation. Chloroform extracts were concentrated to a volume of 50 pi for analysis on silica gel TLC in hexane diethyl ether acetic acid (85 15 1). 

Preparation and analysis of K3(Cr(C204)3].3H20 (Inorg.SynthA 939) 37) This can be prepared by the reduction of potassium dichromate with oxalic acid in presence of oxalate. It is envisaged that the first stage is the reduction of CKVI) to Cr(III), followed by the complex formation with the oxalate. 

Infrared and UV/vis data have been used by several authors to identify the C=C, C=0, and M—O stretches in the complexes synthesized 15, 18-21, 37, 38, 41, 44, 50, 54, 56, 58, 59, 64-66, 69, 74, 78, 80, 82, 103). Except in the initial research on first-row transition metal complexes of squaric acid, where these data were used in proposing structures, IR and UV/vis analysis have been used as supporting evidence for the particular coordination mode of the ligand 19,21,22, 45, 52, 59, 65). Infrared spectroscopy has also been utilized in the study of mixed oxalate/squarate complexes 118), although not to the same extent as in complexes of the oxalate ion. For example, Scott et al. studied the IR properties of Co(III) oxalate complexes with the hgand in a variety of chelating/bridging situations 119). 

Because of the ease of synthesis and industrial importance of diallyl esters much of the research has dealt with the behavior of the isomeric phthalates. Some other dicarboxylic acid esters have been studied by Simpson and Holt [41]. The kinetics of the poljmierization of the diallyl esters of oxalic, malonic, succinic, adipic, and sebacic acid have also been considered. In previous kinetie studies, no differentiation was made between the behavior of the uncyclized monomer (or its free radical) and of the cyclic free-radicals. A priori, differences should have been presumed, but evidently Matsumoto and Oiwa [46] were the first seriously to attempt a kinetic analysis based on the concept that the linear and the cyclic units are two different species. In effect, these two species copolymerize with each other. However, the analysis has not been carried so far as to determine reactivity ratios. 

At first glance, the results appear quite scattered. The values obtained under conditions of chemical ferrioxalate actinometry represent the upper boundary of the reported values, which mostly agree with each other. Between 250 and 350 nm the quantum yields are fairly constant around 1.25. Ferrioxalate actinometry is performed under standardized conditions using millimolar concentrations of ferrioxalate (and above millimolar at A > 436 nm) and an acidic pH (0.05 M H2SO4) of about 1.2 [206]. Other measurements have been carried out at lower initial Fe(III) concentrations as well as different Fe(III) to oxalate ratios and different pH values these mostly result in lower Fe(II)-quantum yields. Some investigations discriminating between individual complexes of Fe(III) and oxalate have been performed, while others did not provide an analysis of the individual complexes and are thus valid only for their respective complex-mixtures. However, all measurements with initial Fe(HI) concentrations below millimolar result in lower quantum yields. It is therefore desirable to characterize systemically any possible effects of initial Fe(III) complex concentration, speciation, and other experimental conditions on the ferrioxalate quantum yield to be able to interpret reported differences. 

---