Pyridine drying

Commercial pyridine dried over potassium hydroxide pellets is satisfactory. 

Haematin /75489-90-47 M 633.5, m200 (dec). crystd from pyridine. Dried at 40° in vacuo. 

Hd61D3tlIl [15489-90-4] M 633.5, m 200 (dec). Crystd from pyridine. Dried at 40° in vacuo/1 Haematoporphyrin dimethyl ester [33070-I2-I] M 626.7, m 212°. Crystd from CHClj/MeOH. 

Pure pyridine dried over barium oxide was used. A considerable amount of heat is liberated on addition of the pyridine to the mixture. 

To a solution of 1 kg (7 moles) of 2-amino-5-nitrothiazole in 5 L of pyridine (dried with potassium hydroxide) was added dropwise for 2-3 hours 8.5 moles of 2-thienoylchloride. N-(5-Nitro-2-thiazolyl)-2-thiophenecarboxamide was prepared as a yellow crystals with melting point 255-256°C. 

Carbohydrate (10 mg) is treated with 1 ml of anhydrous pyridine (dried over KOH),... 

TrichloromethyI)pyridine Dry chlorine (50 g, 3 moles per mole of amine) is led into a mixture of 4-methylpyridine (21 ml), acetic anhydride (20 ml), sodium acetate (60 g), and acetic acid (250 ml) kept at 80°. The mixture is then poured on ice, made alkaline with ammonia, and extracted with ether. Two vacuum-fractionations of the oil obtained from the extract gives 4-(trichloromethyl)pyridine (15.4 g), b.p. 105-107°/18 mm. The product decomposes in a few days it is converted by AgN03 in aqueous acetic acid into isonicotinic acid and by tin in acetone-hydrochloric acid into 4-(dichloromethyl)pyridine. 

Pyridine dried over sobd sodium hydroxide and then redistilled is sufficiently pure for this preparation. More effective drying can lie achieved by use of barium oxide or activated alumina. 

If desired, the approach above may be adapted to semiquantitative analysis of black powder, Pyrodex, or flash powders. A weighed sample, 0.25 g or more, on a tared filter paper is treated several times with a few milliliters of hot water, the filter dried, and the weight loss determined. The loss represents the oxidizer concentration. The filter is treated with pyridine, dried, and reweighed. The weight loss represents sulfur concentration and the residue either charcoal or aluminum as appropriate. 

Pyridine dry (from Sigma-Aldrich or other firms)... 

Partial (3, 97) or complete (98) silylation may be obtained. Hydroxyl groups at C-3, 6a, Ip, and 12 are transformed into silyl ethers when treated with hexamethyldisilazane, 0.03 ml, in dry dimethylformamide, 0.06 ml, at 50 °C for 3hr (77). Complete silylation, both of equatorial and axial hydroyxl groups, is obtained in pyridine(dry)-hexamethyldisilazane-trimethyl-chlorosilane, 10 5 2 (v/v), 15 min, room temperature (98). Prolonged reaction times may give enol silyl ethers with keto bile acids. In an analogous reaction VandenHeuvel and Brady have prepared chloromethyldimethylsilyl ethers (99). Silyl ethers are very readily hydrolyzed. 

Trifluoroacetylation by reaction of Img of the sample with 0.1ml N,N-dimethylformamide and 0.2 ml trifluoroacetic anhydride at room temperature for 10 min and direct injection. Trimethylsilylation 10 mg of the compound was treated in a small stoppered vial with 1ml of anhydrous pyridine (dried with KOH pellets), 0.2 hexamethyldisilazane and 0.1ml trim-ethylchlorosilane. The mixture was shaken vigorously for about 1 min and then kept at room... 

Pyridine dried with Linde 5 A molecular sieve. 

Hexamethyltrisiloxane-1,5-diol, chlorodimethylsilane, dry pyridine, dry THF, hexane, anhydrous magnesium sulfate. 

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