Propionate, determination

Determination of dose-The number of pellets to be implanted depends upon the minimal daily requirement of testosterone propionate determined by a gradual reduction of the amount administered parenterally. The usual ratio is as follows Implant two 75 mg pellets for each 25 mg testosterone propionate required weekly. It has been found that approximately 33% of the material is absorbed in the first month, 25% in the second month, and 17% in the third month. Adequate effect of the pellets ordinarily continues for 3 to 4 months, sometimes as long as 6 months. 

Scheme 1. Ion relationships in silver propionate determined by Ms/Ms. Reproduced with permission from Ref. 56. Copyright 1584, American Chemical Society.

A colourless, odourless, neutral liquid at room temperature with a high dielectric constant. The amount of water present can be determined directly by Karl Fischer titration GLC and NMR have been used to detect unreacted propionic acid. Commercial material of high quality is available, probably from the condensation of anhydrous methylamine with 50% excess of propionic acid. Rapid heating to 120-140° with stirring favours the reaction by removing water either directly or as the ternary xylene azeotrope. The quality of the distillate improves during the distn. 

The ratio of products 15 and 16 is dependent on the structures, base, and the solvent. The kinetics of the reaction is likewise dependant on the structures and conditions of the reaction. Thus addition or cyclization can be the rate-determining step. In a particularly noteworthy study by Zimmerman and Ahramjian, it was reported that when both diastereomers of 20 were treated individually with potassium r-butoxide only as-epoxy propionate 21 was isolated. It is postulated that the cyclization is the rate-limiting step. Thus, for these substrates, the retro-aldolization/aldolization step reversible. ... 

Figure 13.11 Column-switcliing RPLC trace of a surface water sample spiked with eight chlorophenoxyacid herbicides at the 0.5 p-g 1 level 1, 2,4-dichlorophenoxyacetic acid 2, 4-chloro-2-methylphenoxyacetic acid 3, 2-(2,4-diclilorophenoxy) propanoic acid 4, 2-(4-cliloro-2-methylphenoxy) propanoic acid 5, 2,4,5-trichlorophenoxyacetic acid 6, 4-(2,4-dichlorophenoxy) butanoic acid 7, 4-(4-chloro-2-methylphenoxy) butanoic acid 8, 2-(2,4,5-tiichlorophenoxy) propionic acid. Reprinted from Analytica Chimica Acta, 283, J. V. Sancho-Llopis et al., Rapid method for the determination of eight chlorophenoxy acid residues in environmental water samples using off-line solid-phase extraction and on-line selective precolumn switcliing , pp. 287-296, copyright 1993, with permission from Elsevier Science.

The strong interactions between the water molecules also become obvious from NMR measurements by Tsujii et al..57) 13C-NMR experiments were used for determining the microviscosity of water in reversed micelles of dodecylammonium-propionate with 13C glycine cosolubilized. It was found that the apparent viscosity of the water-pool corresponds to the viscosity of a 78 % aqueous glycerol solution, obviously as a consequence of the extended network formation by strong hydrogen bonding. 

The current-potential relationship indicates that the rate determining step for the Kolbe reaction in aqueous solution is most probably an irreversible 1 e-transfer to the carboxylate with simultaneous bond breaking leading to the alkyl radical and carbon dioxide [8]. However, also other rate determining steps have been proposed [10]. When the acyloxy radical is assumed as intermediate it would be very shortlived and decompose with a half life of t 10" to carbon dioxide and an alkyl radical [89]. From the thermochemical data it has been concluded that the rate of carbon dioxide elimination effects the product distribution. Olefin formation is assumed to be due to reaction of the carboxylate radical with the alkyl radical and the higher olefin ratio for propionate and butyrate is argued to be the result of the slower decarboxylation of these carboxylates [90]. 

Houwen FP, C Dijkema, AIM Stams, AJB Zehnder (1991) Propionate metabolism in anaerobic bacteria determination of carboxylation reactions with C-NMR spectroscopy. Biochim Biophys Acta 1056 126-132. 

The various thermal techniques give different results. Snee (1991) determined the heat of the esterification reaction between sec-butanol and propionic aldehyde using different thermal techniques. 

Since the metabolite of clomeprop, 2-(2,4-dichloro-3-methylphenoxy)propionic acid, and inabenfide could not be directly determined by GC, they are derivatized to a more stable compound with diazomethane for the metabolite of clomeprop or with anhydrous chloroacetic acid for inabenfide. 

The official analytical method of the Ministry of Environment, Japan, recommends the use of a Cig cartridge to determine naproanilide. This method consists of the following procedure 5 mL of the 1N hydrochloric acid are added to the water sample and the solution is applied to a Cig cartridge, which is preconditioned with 5 mL each of acetonitrile and water, at a flow rate of 10-20 mL min. Naproanilide and its metabolite, 2-(2-naphthoxy)propionic acid, are eluted with 10 mL of acetonitrile. 

By this method, for example, the absolute configurations of the following compounds were established (-)-2-phenylbutyric acid,[48] (-)-hydratropic acid,[48] (+)-0-acetyl-mandelic acid,t48] (-)-2-(7/-carbazolyl)propionic acid,t48] (+)-1 -phenylethanol,[48] (-)-menthol,t48] (+)-1 -phenylethylamine,[48] and 1-alanine ethylester.[48] The determination of the absolute configuration of bacteriochlorophylles c, d and e was made possible by the esterification of the phaeophorbides by CDI to imidazolides.[49]... 

It may be mentioned that the diastereomers of the analogous compound bearing a hydrogen atom instead of the methoxy group, the (—-)-methyl esters of 3-(methyl-l-naphthylphenylstannyl)propionic acid, could not be separated analogously. Moreover, NMR spectroscopy could not be used as in the former case to determine the diastereomeric ratio. 

Polymer Matrix Effects. In order to approximate the environment experienced by the arylcarbamate moieties in coatings based on aromatic diisocyanates, we chose to study the photochemistry of alkyl N-arylcarbamates in polymethacrylate (PMMA) and polypropyl-methacrylate (PPMA) films. First, however, 2a and 3a were irradiated in ethyl propionate (a model solvent for PMMA and PPMA) to determine the effect of the solvent polarity (dielectric) on the photolysis of the carbamates. Upon excitation at 280 nm, where the solvent absorbance was negligible, is 0.006 for 2a and 0j) is 0.005 for 3a. These values are significantly smaller... 

A UV analysis of the products formed upon photolysis of 2a at 280 nm in ethyl propionate, PMMA, and PPMA further illustrates the effect of the matrix stiffness on the photodecomposition process (Table III). The ratio 0C to b +, j [ c/( b+ d)) is determined by the ratio of absorbance of product 2c to the absorbances of products 2b and 2d [A2c/(A2b+A2d)1 n this case, since the results were tabulated from the actual absorption spectra (difference spectra), the ratio of the products formed in the solvent ethyl propionate can be directly compared to the ratios in PPMA and PMMA. From Table III, it is readily seen that the ratio increases on going from the ethyl propionate solution,... 

The study above does not account for the extra six carbons acquired in the conversion of piperideine (8, 10 carbons) to phlegmarine (9, 16 carbons). It was initially proposed that the carbons were incorporated via pelletierine (12), which was incorporated twice into lycopodine resulting in two symmetrical halves of the alkaloid (Scheme 6.2). However, when 14C-labeled pelletierine (12, label at C2) was fed to the plant, degradation studies of lycopodine revealed that only one half consisted of the 14C label from pelletierine (the half containing C9-C16) [10]. The other half does not result from pelletierine 12 but must be something similar in structure since it does contain the piperideine unit (8) resulting from lysine. It was of interest then to determine the exact source of the three-carbon propionate unit in pelletierine (12). 

NMR-spectroscopic studies and a single crystal X-ray structure determination of the reduced Co / form of 100 revealed the presence of a bridging 2,3-dibromo-3-phenyl-propionato ligand (threo dl pair). The complex bearing the erythro form of 2,3-dibromo-3-phenyl-propionate is only produced in minor yields <3%. Therefore, the bromination of the encapsulated alkene is a highly diastereoselective syu-addition. This is rather... 

Xiao-Hua Yang et al. [ 1 ] determined nanomolar concentrations of individual low molecular weight carboxylic acids (and amines) in seawater. Diffusion of the acids across a hydrophobic membrane was used to concentrate and separate carboxylic acids from inorganic salts and most other organic compounds prior to the application of ion chromatography. Acetic propionic acid, butyric-1 acid, butyric-2 acid, valeric and pyruvic acid, acrylic acid and benzoic acid were all found in reasonable concentrations in seawater. 

Various chromogenic reagents have been used for the spectrophotometric determination of boron in seawater. These include curcumin [108,109], nile blue [110], and more recently 3,5 di-tert butylcatechol and ethyl violet [111]. Uppstroem [108] added anhydrous acetic acid (1 ml) and propionic anhydride (3 ml) to the aqueous sample (0.5 ml) containing up to 5 mg of boron per litre as H3BO3 in a polyethylene beaker. After mixing and the dropwise addition of oxalyl chloride (0.25 ml) to catalyse the removal of water, the mixture is set aside for 15-30 minutes and cooled to room temperature. Subsequently, concentrated sulfuric-anhydrous acetic acid (1 1) (3 ml) and curcumin reagent (125 mg curcumin in 100 ml anhydrous acetic acid) (3 ml) are added, and the mixed solution is set aside for at least 30 minutes. Finally 20 ml standard buffer solution (90 ml of 96% ethanol, 180 g ammonium acetate - to destroy excess of protonated curcumin - and 135 ml anhydrous acetic acid diluted to 1 litre... 

Horikawa [126] has adapted a thermal detector for the determination of formic, acetic, and propionic acids by liquid chromatography. 

Gorcharova and Khomenko [127] have described a column chromatographic method for the determination of acetic, propionic, and butyric acids in seawater, and thin-layer chromatographic methods for determining lactic, aconitic, malonic, oxalic, tartaric, citric, and malic acids. The pH of the sample is adjusted to 8 - 9 with sodium hydroxide solution. It is then evaporated almost... 

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