Pyridine purification

The polysaccharide was acetylated with acetic anhydride in the presence of pyridine. Purification of the acetate consisted in precipitation of a 10% boiling benzene solution with petroleum ether. One hundred and fifty such precipitations were necessary before a constant-rotating product resulted [a]D20 = — 20.1° (c = 1.0, chloroform). Cryoscopic molecular weight determinations in benzene solution gave an average value of 3918. 

Methyl -propyl ketone, 340 Methyl pyridines, purification of, 177-179 N-Methylpyrrole, 837, 838 Methyl red, 621, 625 sodium salt of, 626 Methyl salicylate, 780,782 Methyl sulphite, 304 2-Methylthiophene, 836 Methyl p-toluenesulphonate, 825 Methylurea, 968, 969 Methylene bromide, 300 Methylene chloride, purification of, 176 3 4-Methylenedioxycinnamic acid, 711, 719... 

In Europe, where an abundant supply of anthracene has usually been available, the preferred method for the manufacture of anthraquinone has been, and stiU is, the catalytic oxidation of anthracene. The main problem has been that of obtaining anthracene, C H q, practically free of such contaminants as carbazole and phenanthrene. Many processes have been developed for the purification of anthracene. Generally these foUow the scheme of taking the cmde anthracene oil, redistilling, and recrystaUizing it from a variety of solvents, such as pyridine (22). The purest anthracene may be obtained by azeotropic distillation with ethylene glycol (23). 

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

The N-oxide function has proved useful for the activation of the pyridine ring, directed toward both nucleophilic and electrophilic attack (see Amine oxides). However, pyridine N-oxides have not been used widely ia iadustrial practice, because reactions involving them almost iavariably produce at least some isomeric by-products, a dding to the cost of purification of the desired isomer. Frequently, attack takes place first at the O-substituent, with subsequent rearrangement iato the ring. For example, 3-picoline N-oxide [1003-73-2] (40) reacts with acetic anhydride to give a mixture of pyridone products ia equal amounts, 5-methyl-2-pyridone [1003-68-5] and 3-methyl-2-pyridone [1003-56-1] (11). 

Chlorophyll b [519-62-0] M 907.52, sinters at 86-92 , sinters at 170 , dec at 160-170 , m 183-185 , 190-195 , [alj, -267 (Me2CO + McOH), [a] j-133 (McOH + Pyridine 95 5). See purification of chlorophyll a, and is separated from "a" by chromatography on sucrose [UV, IR Stoll and Weidemann Helv Chim Acta 42 679, 681 7959]. It forms red-black hexagonal bipyramids or four sided plates from dilute EtOH and has been recrystd from CHCl3-MeOH. It is soluble in MeOH, EtOH, EtOAc and insoluble in pet ether. [J Am Chem Soc 88 5037 1966.]... 

Commercial pyridine (J. T. Baker Chemical Company) was used without purification. 

This group was developed for terminal protection of an oligonucleotide sequence for purposes of monitoring the purification by HPLC after a synthesis. It shows characteristic UV maxima at 365 and 380 nm. The group is prepared from the chloride in pyridine and can be bound directly to the support-bound oligonucleotide. ... 

To a mixture of naphthyloxazoline 71 (4.31 g, 12.97 mmol) in pyridine (4 mL) was added activated copper (1.99 g). The mixture was heated to reflux for 24 h then was cooled to rt, diluted with CH2CI2 and washed with aqueous ammonia until the copper had been completely removed. The organic phase was washed with water then dried over anhydrous magnesium sulfate, filtered, and concentrated to afford the title compound as a tan solid. This material was used without further purification. 

A mixture of 125 g of o-(pethyl chlorocarbonate in 150 ml of ether. The mixture is kept at room temperature for 3 days, diluted with about 500 ml of water and extracted with 300 ml of ether. The ethereal extract Is washed with 300 ml of water, dried over calcium chloride, filtered and concentrated. The resulting ethyl o-(pnext step without further purification. 

A mixture of 50 g of betamethasone, 50 cc of dimethylformamide, 50 cc of methyl orthobenzoate and 1.5 g of p-toluenesulfonicacid Is heated for 24 hours on oil bath at 105°C while a slow stream of nitrogen is passed through the mixture and the methanol produced as a byproduct of the reaction is distilled off. After addition of 2 cc of pyridine to neutralize the acid catalyst the solvent and the excess of methyl orthobenzoate are almost completely eliminated under vacuum at moderate temperature. The residue Is chromatographed on a column of 1,500 g of neutral aluminum oxide. By elution with ether-petroleum ether 30 g of a crystalline mixture are obtained consisting of the epimeric mixture of 170 ,21 -methyl orthobenzoates. This mixture is dissolved without further purification, in 600 cc of methanol and 240 cc of methanol and 240 cc of aqueous 2 N oxalic acid are added to the solution. The reaction mixture is heated at 40°-50°C on water bath, then concentrated under vacuum. The residue, crystallized from acetone-ether, gives betamethasone 17-benzoate, MP 225°-231°C. 

A mixture of 1.759 g of 2a.3a-epithio-5Q -endrostan-17 3-ol, 2.3 ml of 1-methoxycyclopen-tene, 20 mg of pyridine salt of p-toluenesulfonic acid and 20 ml of t-butanol is stirred for 4 hours at room temperature. The reaction mixture is poured into an aqueous solution of sodium carbonate and the whole extracted with dichloromethane. The extract is dried over anhydrous sodium sulfate and evaporated to remove solvent. Purification of the residue by chromatography over alumina gives 1.487 g of 17/3-(1-methoxycyclopentyl)oxy-2a,3a-epi-thio-50 -androstane. Yield68.2%. MP98°Cto 101°C. 

A mixture of 10.5 grams of 1-ethylcytosine, 18.6 grams of N-acetylsulfanilyl chloride, and 50 ml of pyridine is stirred at room temperature for 2 days. The precipitated solid is removed by filtration, and the filtrate is evaporated at 60°C under reduced pressure to a syrup. The syrup is triturated with 0.25 N hydrochloric acid, and the solid N-(N-acetyl-sulfanilyl)-1-ethylcytosine obtained is isolated and dried. This solid is suitable for use without further purification. 

Pyridine Perchlorate is almost as powerful as TNT (Pb block expansion 95% TNT, 87% PA), but is much more sensitive to impact (FI 40% PA), being comparable to PETN in this respect (Refs 4 5). Kuhn (Ref 7) states that it can be detonated on impact, but is normally considered a stable intermediate, suitable for purification of pyridine. Occasionally explns have occurred when the salt was disturbed (Ref 11), which have been variously attributed to the presence of ethyl perchlorate, AP or chlorates. A safer preparative modification is described (Ref 8). It explds on heating to above 335°, or at a lower temp if AP is present (Ref 10). According to Mellor (Ref 9), the salt can expld violently in contact with metals, while Zacherl (Ref 6) describes a lab expln which occurred during the distn of pyridine liberated from its perchlorate... 

The GMT in human serum reacts most rapidly with Y-glutamyl-p-nitroanilide at pH 8.2. The same activity is found in 2-amino-2-methylpropane-l 3 diol, diethanolamine, triethanolamine and tris buffers. Magnesium ions have no effect on the activity but favor the solubilization of the substrate. Bondar and Moss (54) found that free glutamate, due to elevated serum glutamate concentrations or glutamate released by substrate breakdown, increases the apparent GMT activity. They concluded that the assay should be performed in the presence of 1.0 vM/1 glutamate in order to reduce the possibility of falsely elevated results. This was not observed by others. Rowe and co-workers have indicated that certain batches of p-nitroanilide substrate contain impurities which may reduce GMT activity and increase the values ( ). Huesby and Stromme (56) confirmed the presence of such impurities and recommended pyridine extraction for substrate purification. 

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