Formamide, purification

Halomycins. The halomycins are a group of four antibiotics produced by M.icromonospora halophjtica and separated by partition chromatography on Chromosorb W coated with formamide (19). Further purification was accompHshed using preparative dc (212). 

The residue is triturated with methanol to afford a crystalline solid. This material contains no detectable amount of starting material by paperstrip chromatography but shows two UV absorbing spots near the solvent front (methanol-formamide 2 1 vs benzene-n-hexane 1 1). An aliquot is recrystallized three times from a mixture of benzene and n-hexane to give 17a,20,20,21-bis(methylenedioxy)-11(3-hydroxy-6,16a-dimethyl-4,6-pregnadiene-3-one which is used in the subsequent step of the synthesis without further purification. 

Wang resin was purchased from Advanced ChemTech (1% DVB, 0.70mmol/g substitution, 100-200 mash, Cat. SA5009). Anhydrous tetrahydrofuran (THF), A/A-dimcthyl-formamide (DMF), methanol, dichloromethane, pyridine, 1,1 -carbonyldiimidazole (CDI), piperazine, homopiperazine, trans-1,4-diaminocyclohexane, 4-(dimethylamino)pyridine (DMAP), succinic anhydride, diglycolic anhydride, 3-methyl-glutaric anhydride, 2-aminophenol, 2-amino-p-cresol, 2-amino-4-tert-butyl phenol, /V-methylmorpholine (NMM), triphenylphosphine, diethyl azodicarboxylate (DEAD), and trifluoroacetic acid (TFA) were purchased from Aldrich Chemical Company, Inc. and used without further purification. PyBOP was purchased from Novabiochem. 

Materials. Reagent grade solvents, dimethyl formamide (DMF), dimethyl acetamide (DMAC), dimethyl sulfoxide (DMSO) and methanol were purchased from Baker, stored over molecular sieves once opened, and used without further purification. Aminoethane thiosulfuric acid (AETSA) purchased from Kodak, and Taurine, purchased from Alfa were purified by recrystallization. Each was thrice recrystallized from hot, deionized water. The crystalline precipitate was dried (48 hours at 40 °C) in-vacuo and subsequently stored in a desiccator. Benzophenone (BP) was purchased from Aldrich Chemical Company. QUANTACURE BTC (BTC), (4-benzolybenzyl) trimethylammonium chloride, was used as supplied by Aceto, Inc., Flushing, New York. Phenyl glycidyl ether (PGE) was purchased from MCB, distilled in-vacuo. and stored at -15 °C. Epon 828 was used as supplied bv Shell Chemical Company. The epoxy equivalent weight (EEW) for Epon 828 determined by an appropriate titration, was found to be 187.7. 

Fresh bottles of benzaldehyde (99%), formamide (99+%) and chlorotrimethylsilane (98%) from the Aldrich Chemical Company. Inc., were used without further purification. 

Some of the stimulus for studying these systems arose from the availability and use of some of these ligands as solvents, a subject reviewed by Vaughan38 who includes details of methods of purification and electrochemical parameters. The dielectric constants are much higher when these molecules contain an N—H bond thah when they are JV.V -dimethyl substituted. Formamide, its V-methylated derivaties and dimethylacetamide (DMA) are liquids at room temperature iV-methyl-... 

The traditional methods utilize sulfur or phosphorous halides to convert the acid to die acid chloride. Of these methods, thionyl chloride [often with a catalytic amount of dimethyl formamide (DMF)] is the most useful since the by-products of die reaction are gases (SO2, HC1) which can be easily purged from the reaction mixture with a stream of nitrogen. The acid chloride product can then be purified on a small scale by bulb-to-bulb distillation or crystallization. Because an excess of thionyl chloride is usually used, there must be a purification step to remove the excess reagent. 

Formamide is an excellent solvent for many polar organic compounds and for a selection of inorganic salts. It is very hygroscopic and readily hydrolysed by acids or bases. The commercial product frequently contains formic acid, water and ammonium formate. Purification may be effected by passing ammonia gas into the solvent until a slight alkaline reaction is obtained addition of dry acetone then precipitates the ammonium formate. The filtered solution is dried over magnesium sulphate and fractionally distilled under reduced pressure distillation at atmospheric pressure causes decomposition. Pure formamide has b.p. 105 °C/11 mmHg. 

To a cooled (0°C) solution of formamide (30.5 mL, 0.76 mol) in 1 L of diethyl ether was added 89 g (0.19 mol) of phosphorous pentasulfide in small portions with stirring. The reaction mixture was allowed to warm to ambient temperature, stirred for 2 h, filtered, and concentrated in vacuo to afford thioformamide as a yellow offensive smelling oil which was used without purification. 

Materials. Spectroscopic-grade solvents were used where fluorescence or contact angle measurements were to be made, appropriate purification steps were taken. The tetrahydrofuran was distilled from lithium aluminum hydride. For contact angle measurements, the following liquids and their surface tensions (dynes/cm.) at 20° were used water, 72.6 formamide, 58.2 ethylene glycol, 47.7 methylene iodide, 50.8 1-bromonaphthalene, 44.6 and n-hexadecane, 27.6. 

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