Pyridine-2-acetic acid

Two surprising observations were made in the course of this work first that the enol acetate (5) is stable under the conditions for formation of (6) from (4) second, that the course of the buffered bromination of (5) depends on the conditions used. Thus, in the presence of epichlorohydrin, (7) is the sole isomer produced, whereas in pyridine-acetic acid approximately equal amounts of (7) and (8) are formed. It was suggested that this difference is inherent in the mechanism and not a result of isomerization of (7) to (8) during the course of the reaction. 

This was also accomplished with BaRu(0)2(OH)3. The same type of conversion, with lower yields (20-30%), has been achieved with the Gif system There are several variations. One consists of pyridine-acetic acid, with H2O2 as oxidizing agent and tris(picolinato)iron(III) as catalyst. Other Gif systems use O2 as oxidizing agent and zinc as a reductant. The selectivity of the Gif systems toward alkyl carbons is CH2 > CH > CH3, which is unusual, and shows that a simple free-radical mechanism (see p. 899) is not involved. ° Another reagent that can oxidize the CH2 of an alkane is methyl(trifluoromethyl)dioxirane, but this produces CH—OH more often than C=0 (see 14-4). ... 

Singh utilized anionic dyes to detect gramicidin on paper chromatograms184. Paris and Theallet described three paper chromatographic systems for gramicidin185. Ritschel and Lercher described two solvent systems for antibioticsiOD. The solvent systems were butanol-pyridine-acetic acid-water (15 10 3 12) and water saturated butanol-water saturated ethyl ether-acetic acid (5 1 1) on Schleicher and Schull 2043b paper. The antibiotics were visualized by ninhydrin. 

Toyo No.50 Descending for 9 hrs. n-Butanol/pyridine/ acetic acid/water (15 10 3 12)... 

Cabon tetrachloride, n-hexane, chloroform, ACN, acetone, THF, pyridine, acetic acid, and their various mixtures were applied as mobile phases for adsorption TLC. Methanol, 1-propanol, ACN, acetone, THF, pyridine and dioxane served as organic modifiers for RP-TLC. Distilled water, buffers at various pH (solutions of and dipotassium hydrogen phosphate or potassium dihydrogen phosphate) and solutions of lithium chloride formed the aqueous phase. Carotenoids were extracted from a commercial paprika sample by acetone (lg paprika shaken with 3 ml of acetone for 30 min), the solution was spotted onto the plates. Development was carried out in a sandwich chamber in the dark and at ambient temperature. After development (15 cm for normal and 7cm for HPTLC plates) the plates were evaluated by a TLC scanner. The best separations were realized on impregnated diatomaceous earth stationary phases using water-acetone and water-THF-acetone mixtures as mobile phases. Some densitograms are shown in Fig.2.1. Calculations indicated that the selectivity of acetone and THF as organic modifiers in RP-TLC is different [14],... 

Goethite CO2 SO2 pyridine, acetic acid vapour, CO2, nitric oxide, trimethyl chlorosilane Russell et ah, 1975 Kaneko and Inouye, 1981 Rochester and Topham, 1979 c... 

Even higher viscosities are typical for polyimides based on tetranuclear diamines, e.g., 4,4 -di-(p-aminophenoxy)-benzophenone and l,l-dichloro-2,2 di(/ -aminophenoxy)-ethylene. Polyimides were prepared according to the method for the synthesis of PCA by low-temperature polycondensation in NMP. Polyimides were prepared by catalytic cyclodehydration of PCA directly in the reaction solutions using the catalytic system pyridine-acetic acid anhydride (1 1) [22] (Scheme 3.5). 

Fuller s earth (hydrated aluminosilicate) Magnesium oxide Charcoal Alumina Magnesium trisilicate Silica gel Calcium hydroxide Magnesium carbonate Calcium phosphate Calcium carbonate Sodium carbonate Talc Inulin Sucrose = starch Petroleum ether, b 40-60°- Petroleum ether, b 60-80°. Carbon tetrachloride. Cyclohexane. Benzene. Ethyl ether. Chloroform. Ethyl acetate. Acetone. Ethanol. Methanol. Pyridine. Acetic acid. 

Octaethylporphinato complexes of the type [M(OEP)(02CMe)2] (M = Zr or Hf) have been prepared by reaction of H2OEP and [M(acac)4] in molten phenol at 210-240 °C followed by crystallization from pyridine-acetic acid-water mixtures. The complexes have been characterized by IR and mass spectra703,704 and by electronic absorption and emission spectra.703 They have an eight-coordinate square antiprismatic structure (48) in which the four porphinato nitrogen atoms occupy the coordination sites on one square face and the two bidentate acetate... 

Mg and Cd are easily dissociated from their porphyrazine complexes in acetic acid.188,190 Demetallation of Mg- and Cd-Ph8Tap in pyridine-acetic acid is first order in the metal complexes and second order in the solvated proton. Similar results are reported on the Zn- and Ni-Ph8Tap-DMS0-H2S04 H20 system. 

For the optimum HPLC separation, the liquid chromatograph was connected to a mass detector. A column (250 X 5-mm ID) of SPHERISORB C8 (5-yttm particles) was eluted with a solvent gradient, with reservoir A containing methanol and reservoir B containing water-pyridine-acetic acid (98.5 1.5 0.025). The mobile phase was A B = 92 8, and this composition was held for 10 min. The flow rate was 0.75 ml/min. 

In 1983, Barton et al. described a new procedure for the oxidation of saturated hydrocarbons [1] by the use of metallic iron, adamantane, hydrogen sulfide or sodium sulfide, pyridine, acetic acid and a small amount of water. The reactions were run under air and afforded adamant-l-ol together with a mixture of adamant-2-ol and adamantanone. The substrate scope could be extended to other hydrocarbons. However, all of them led to product mixtures of the corresponding alcohol(s) and ketone (Scheme 3.1). 

Table 4.5). The first was the three-dimensional procedure of Hartley (ref. 332) which employs the following three solvents 1) 1.5% (v/v) formic acid 2) benzene-acetic acid (9 1, v/v) 3) ethyl acetate-methanol-acetic acid (20 1 1, by vol.). The second method was the one-dimensional procedure of Morse and Horecker (ref. 333) and employed a modified solvent system containing benzene-pyridine-acetic acid (80 20 2) with 25 pi 2-mercaptoethanol added per 50 ml of solvent. 

At least two systems can be cited as catalysts of peroxide oxidation the first are the iron (III) porphyrins (44) and the second are the Gif reagents (45,46), based on iron salt catalysis in a pyridine/acetic acid solvent with peroxide reagents and other oxidants. The author s opinion is that more than systems for stress testing these are tools useful for the synthesis of impurities, especially epoxides. From another point of view, they are often considered as potential biomimetic systems, predicting drug metabolism. Metabolites are sometimes also degradation impurities, but this is not a general rule, because enzymes and free radicals have different reactivity an example is the metabolic synthesis of arene oxides that never can be obtained by radical oxidation. 

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