Dimethylacetamide

The rate of hydrolysis of DMAC is very low, but increases somewhat in the presence of acids or bases. DMAC is a stable compound, but is mildly hygroscopic and desiccation and/or dry nitrogen blanketing of storage vessels are sometimes used to reduce water pick-up. In the absence of water, acids, or bases, DMAC is stable at temperatures up to its hoiling point at atmospheric pressure. Its greater stability enables more economical recovery by distillation relative to that of other similar solvents. 

The chemical reactions of DMAC are typical of those of disubstituted amides. Under suitable conditions, DMAC will react as follows  

Dimethylacetamide can be produced by the reaction of acetic acid [64-19-7J and dimethylamine [124 0-3J  

The product of this reaction can be removed as an azeotrope (84.1% amide, 15.9% acetic acid) which boils at 170.8—170.9°C. Acid present in the azeotrope can be removed by the addition of soHd caustic soda [1310-73-2] followed by distillation (2). The reaction can also take place in a solution having a DMAC-acetic acid ratio higher than the azeotropic composition, so that an azeotrope does not form. For this purpose, dimethylamine is added in excess of the stoichiometric proportion (3). If a substantial excess of dimethylamine reacts with acetic acid under conditions of elevated temperature and pressure, a reduced amount of azeotrope is formed. Optimum temperatures are between 250—325°C, and pressures in excess of 6200 kPa (900 psi) are requited (4). DMAC can also be made by the reaction of acetic anhydride [108-24-7] and dimethylamine  

Dimethylamine is added somewhat in excess of the stoichiometric proportion in this synthesis. Another method employs the reaction of methyl acetate [79-20-9] and dimethylamine  

The chemical reactions of DAIAC are typical of those of disubstituted amides 

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Dimeihylamine, C2H7N, (CH3)2NH. Colourless, inflammable liquid with an ammoniacal odour, mp -96" C, b.p. 7°C. Occurs naturally in herring brine. Prepared in the laboratory by treating nitrosodimetbyl-aniline with a hot solution of sodium hydroxide. Dimethylamine is largely used in the manufacture of other chemicals. These include the solvents dimethylacetamide and dimethyl-formamide, the rocket propellant unsym-metrical dimethylhydrazine, surface-active agents, herbicides, fungicides and rubber accelerators. 

DMF replacement [FORMIC ACID AND DERIVATIVES - DITffiTHYLFORMAMIDE] (Vol 11) N,N-Dimethylacetamide... 

Dimethylacetamide is available in dmms with a capacity of 0.208 m (55 gal), 186 kg net, and in tank cars or tmcks. Although the DOT classifies DMAC as a combustible Hquid, no DOT label is requited. 

Resin and Polymer Solvent. Dimethylacetamide is an exceUent solvent for synthetic and natural resins. It readily dissolves vinyl polymers, acrylates, ceUulose derivatives, styrene polymers, and linear polyesters. Because of its high polarity, DMAC has been found particularly useful as a solvent for polyacrylonitrile, its copolymers, and interpolymers. Copolymers containing at least 85% acrylonitrile dissolve ia DMAC to form solutions suitable for the production of films and yams (9). DMAC is reportedly an exceUent solvent for the copolymers of acrylonitrile and vinyl formate (10), vinylpyridine (11), or aUyl glycidyl ether (12). 

Crystallization and Purification Solvent. Dimethylacetamide is useful ia the purification by crystallization of aromatic dicarboxyHc acids such as terephthahc acid [100-21-0] and/vcarboxyphenylacetic acid [501-89-3]. These acids are not soluble ia the more common solvents. DMAC and dibasic acids form crystalline complexes containing two moles of the solvent for each mole of acid (16). Microcrystalline hydrocortisone acetate [50-03-3] having low settling rate is prepared by crystallization from an aqueous DMAC solution (17). 

Complexes of DMAC and many inorganic haHdes have been reported (20). These complexes are of iaterest because they catalyze a number of organic reactions. Complexes of DMAC and such heavy metal salts as NiBr2 exert a greater catalytic activity than the simple salts (21). The crystalline complex of SO and dimethylacetamide has been suggested for moderating the reaction conditions ia sulfation of leuco vat dyestuffs (22). 

Dimethylacetamide, Material Safety Data Sheet, E.I. du Pont de Nemours and Co., Inc., Wilmington, Del., 1988. 

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