Formamide, decomposition

The reaction is mn for several hours at temperatures typically below 100°C under a pressure of carbon monoxide to minimise formamide decomposition (73). Conversions of a-hydroxyisobutyramide are near 65% with selectivities to methyl a-hydroxyisobutyrate and formamide in excess of 99%. It is this step that is responsible for the elimination of the acid sludge stream characteristic of the conventional H2SO4—ACH processes. Because methyl formate, and not methanol, is used as the methylating agent, formamide is the co-product instead of ammonium sulfate. Formamide can be dehydrated to recover HCN for recycle to ACH generation. 

The C-Si bond of an SMA can also be cleaved by oxidizing reagents like cerium ammonium nitrate (CAN). Starting from (V-bis(trimethylsilyl)methylazetidinones, treatment with CAN probably leads to the oxidation product of the two C-Si bonds, i.e., the corresponding disilylketal that is hydrolyzed into the formamide to give the N-H azetidinones (yields >80%). This constitutes an alternate and more efficient way to sequential fluoride-induced desilylation. Peterson olefination, ozonolysis, and formamide decomposition when deprotection of bis(trimethylsilyl)methylated azetidinones into NH-azetidinones is required.228,230... 

U.S. Patent 4,869,889 by M. B. Sherwin and Jow-Lih Su covers an improved process by combining the exothermic methanol ammoxidation with the endothermic formamide decomposition. 

Formamide decomposes thermally either to ammonia and carbon monoxide or to hydrocyanic acid and water. Temperatures around 100°C are critical for formamide, in order to maintain the quaUty requited. The lowest temperature range at which appreciable decomposition occurs is 180—190°C. Boiling formamide decomposes at atmospheric pressure at a rate of about 0.5%/min. In the absence of catalysts the reaction forming NH and CO predominates, whereas hydrocyanic acid formation is favored in the presence of suitable catalysts, eg, aluminum oxides, with yields in excess of 90% at temperatures between 400 and 600°C. 

The characteristics of this product are as follows. It is a pale yellow, nonodorous, slightly bitter, crystalline powder, very soluble in water (>1.5 g/cc), soluble in methanol and formamide, slightly soluble in ethanol and isopropanol, insoluble in ether, benzene and chloroform MP 162° to 163°C with decomposition uncorrected). 

A mixture of 5.7 grams (0.02 mol) of 5-chloro-2,4-disulfamylaniline and 4.9 grams (0.04 mol) of dichloroacetaldehyde in 25 ml of dimethyl formamide was heated at the boiling temperature and under reflux for 30 minutes. The reaction mixture was thereafter poured into a mixture of ice and water to precipitate the desired 6-chloro-7-sulfamyl-3-dichloro-methyl-3,4-dihydro-1,2,4-benzothiadiazine-1,1-dioxide as a crystalline solid melting at 250° to 270°C with decomposition. 

A Fischer reagent had been made with pyridine, iodine, sulphur trioxide and formamide, instead of methanol. The bottle detonated after being stored for a couple of months. The authors put it down to the decomposition of formamide into ammonia and carbon oxide, which created the overpressure that caused the bottle to detonate. 

In formamide, acetone, and nitromethane the bromide ion is the most mobile of the halides. The difference is slight in nitromethane, but pronounced in the other two solvents. Because mobilities reflect a variety of factors it is possible that opposing effects could result in an ion of intermediate size being more mobile than others in the series. Another possible factor could be the presence of impurities in formamide and acetone, formamide because of decomposition on standing even a short time, and acetone because of the difficulty in removing last traces of water. The presence of impurities could have a significant but unpredictable effect on mobilities. 

Thermal decomposition of formamide at elevated temperatures and reduced pressure ... 

Solid Mo02Br2(DMF)2 melts at 139-141°C with decomposition. The IR spectrum, taken as a KBr dispersion, has characteristic bands for i moO 903 and 940 cm The NMR spectrum in acetone-t/g exhibits signals at S 3.03 (s, 3H, CHa), 3.22 (s, 3H, CH3), 8.26 (s, IH, CH). The complex is insoluble in hexane and diethyl ether and is soluble in methanol, ethanol, dichloromethane, chloroform, acetone, dimethyl formamide, and dimethyl sulfoxide. It is stable in air at room temperature and can be manipulated without special care. This product is specially useful for the synthesis of a number of adducts with pyridine and related bases, since the dimethyl formamide displaced can be readily removed by washing with most common organic solvents. 

It is remarkable that thermal decomposition in polar solvents (dimethyl formamide, tetrahydrofuran) gives pentyl cyanide whereas in a nonpolar solvent (decane, 150°) pentyl cyanide is formed together with pentyl isothiocyanate in a 4 1 molar ratio. The same ratio is obtained on injecting 5-pentylthiatriazole into glass wool heated at 350° in an evacuated flask. 

These proposed equilibria are supported by changes in the IR spectra of the hydroxycarbonyl in solvents of different polarity. In benzene the spectrum corresponds to the covalent species MCOOH, while in the highly polar solvent formamide, the spectrum corresponds to MCO+, with hydroxide as the counterion. The decomposition of this iron hydroxycarbonyl proceeds rapidly upon warming in benzene. In contrast, the potassium salt does not readily decarboxylate in formamide. This indicates that in this system the decarboxylation involves transfer of the hydrogen to the metal. 

Current views on polymerization of acrylonitrile in homogeneous solution are illustrated by a description of the reaction in N,N-dimethyl-formamide (DMF) as initiated by azobisisobutyronitrile (AIBN) at about SO to 60°. Primary radicals from the decomposition of AIBN react with monomer to start a growing chain. About one-half of the primary radicals are effective, the others being lost in side reactions not leading to polymer. Bevington and Eaves (32) estimated initiator efficiency by use of AIBN labelled with C-14, whereas Bamford, Jenkins and Johnson (13) used the FeCls termination technique. Both of these methods require that the rate of AIBN decomposition be known, and the numerical value of this rate has undergone a number of revisions that require recalculation of efficiency results. From recently proposed rate expressions for AIBN decomposition at 60° (22, 136) one calculates an efficiency of about 40% by the tracer technique and 60—65% by the FeCl3 method. 

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. 

This overall reaction is already carried out industrially via the intermediate forma-mide (HCONH2) which, together with the use of disparate operating conditions (high pressures and mild temperatures for formamide synthesis, vacuum and high temperatures for its decomposition), overcomes the unfavorable thermodynamics of... 

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