Dimethylamine

Description

Dimethylamine is a colourless flammable gas at room temperature. It has a pungent, fishy, or ammonia-like odour at room temperature and is shipped and marketed in compressed liquid form. It is very soluble in water and soluble in alcohol and ether. It is incompatible with oxidising materials, acrylaldehyde, fluorine, maleic anhydride, chlorine, or mercury. Dimethylamine is a precursor to several industrially important compounds. For instance, it used in the manufacture of several products, for example, for the vulcanisation process of rubber, as detergent soaps, in leather tanning, in the manufacture of pharmaceuticals, and also for cellulose acetate rayon treatment.

dimethylamine structure

Chemical Properties

Dimethylamine reacts readily with acids to produce salts due to the presence of the unshared electron pair on the nitrogen atom. Similarly, dimethylamine reacts with acid anhydrides, halides, and esters, with CO₂ or CS₂, or with isocyanic or isothiocyanic acid derivatives. It can also react with nitrite, especially under acidic conditions, and possibly nitrogen oxides (Iqbel 1986) to form N-nitrosodimethylamine, a potent carcinogen in various animal species and a suspect human carcinogen (ATSDR 1989; Scanlan 1983; Zeisel et al 1988). N-Nitrosodimethylamine also can be formed upon storage of aqueous dimethylamine solutions or formulations of the dimethylamine salts of the herbicides 2,4D and MCPA (Wigfield and McLenaghan 1987a,b). Dimethylamine also can be nitrosated photochemically in aqueous solutions containing nitrite with the reaction occurring most readily at alkaline pH (Ohta et al 1982).

Physical properties

Clear, colorless liquid or gas with a strong, ammonia-like odor. Odor threshold concentrations of 33 ppb_v and 47 ppb_v were experimentally determined by (Leonardos et al., 1969) and Nagata and Takeuchi (1990), respectively.

Uses

Dimethylamine is used in the manufactureof N-methylformamide, N-methylacetamide,and detergent soaps; in tanning; and as anaccelerator in vulcanizing rubber. It is commercially sold as a compressed liquid intubes or as a 33% aqueous solution..

Uses

Manufacture of pharmaceuticals; stabilizer in gasoline; in production of insecticides and fungicides; in manufacture of soaps and surfactants

Uses

Dimethylamine is a used as a precursor to several industrially significant compounds. It reacts with carbon disulfide to give dimethyl dithiocarbamate, a precursor to a family of chemicals widely used in the vulcanization of rubber. It is raw material for the production of many agrochemicals and pharmaceuticals, such as dimefox and diphenhydramine, respectively.

Production Methods

Methods used commercially for the large-scale production of dimethylamine are generally those used for methylamine synthesis (HSDB 1989). The most widely used process involves heating ammonium chloride and methyl alcohol to about 300°C in the presence of a dehydrating catalyst such as zinc chloride. Dimethylamine has also been prepared from methanol and ammonia or by the catalytic hydrogenation of nitrosodimethylamine (Schweizer et al 1978). It is usually marketed in compressed liquid (anhydrous) form or as a 25-60% aqueous solution.
Dimethylamine is also naturally present in biological systems, probably being formed as a breakdown product from trimethylamine N-oxide (Timofievskaja 1984). Thus it is present in gastric juice of humans, rats, dogs and ferrets at concentrations of 12.6 ± 14 nmol/ml (Zeisel et al 1988); it is a constituent of most foods, especially seafood including squid and octopus, frequently eaten in traditional Chinese and Japanese diets, where it reaches concentrations of 946-2043 p.p.m. (Lin et al 1983,1984). Food processing and cooking markedly increases the dimethylamine contents of foods by increasing the breakdown of constituents such as trimethylamine N-oxide and sarcosine (Lin et al 1983, 1984; Lin and Hurng 1985). Dimethylamine occurs in the air of iron foundries where the amine was used in the casting process (Hansen et al 1985) and also is released from plastic material used in construction (Kiselev et al 1983).
Nitrosation of dimethylamine occurs forming the carcinogenic N-nitrosodimethylamine upon storage of anhydrous and aqueous solutions of dimethylamine or formulations of the dimethylamine salts of the herbicides 2,4-dichlorophenoxyacetic acid (2,4D), 4-chloro-2-methylphenoxyacetic acid (MCPA) and 3,6-dichloro- 2-methoxybenzoic acid (dicamba) (Wigfield and McLenaghan 1987a,b). The volatile N-nitrosodimethylamine is also formed in foods by reaction of dimethylamine with sodium nitrite added as a preservative or by reaction with atmospheric nitrogen oxides during food processing (ATSDR 1989; Gross and Newberne 1977; Scanlan 1983). Concentrations of the nitrosoamine in cheese, apple cider, milk, cereals, vegetables, seafood, cured meats, etc. range between 0.05 and 130 p.p.b. (ATSDR 1989).

Definition

ChEBI: A secondary aliphatic amine where both N-substituents are methyl.

Air & Water Reactions

Highly flammable. Water soluble.

Reactivity Profile

DIMETHYLAMINE is a base, neutralizing acids in exothermic reactions, and a reducing agent. Dimethylamine is temperature sensitive. Reacts vigorously with mercury and chlorine . Reacts violently with strong oxidizing agents and attacks copper and copper compounds [Handling Chemicals Safely, 1980 p. 123]. Reacts with hypochlorites to give N-chloroamines, some of which are explosives when isolated [Bretherick, 1979 p. 108].

Hazard

Dimethylamine is an irritant, with a TLV of 10 ppm in air. The four-digit UN identification number is 1032. The NFPA 704 designation is health 3, flammability 4, and reactivity 0. The primary uses are in electroplating and as gasoline stabilizers, pharmaceuticals, missile fuels, pesticides, and rocket propellants.

Health Hazard

Dimethylamine is a strong irritant to the eyes,skin, and mucous membranes. Spill of liquidinto the eyes can cause corneal damage andloss of vision. Skin contact with the liquidcan produce necrosis. At sublethal concentra tions, inhalation of dimethylamine producedrespiratory distress, bronchitis, pneumonitis,and pulmonary edema in test animals. Theacute oral toxicity was moderate, greater thanfor monomethylamine.
LC50 value, inhalation (rats): 4540 ppm/6 hLD50 value, oral (mice): 316 mg/kg
Buckley and coworkers (1985) have investigated the inhalation toxicity of dimethylamine in F-344 rats and B6C3F1 mice.Animals exposed to 175 ppm for 6 h/day,5 days/week for 12 months showed significant lesions in the nasal passages. Rats developed more extensive olfactory lesions thandid mice. The study indicated that olfactory sensory cells were highly sensitive todimethylamine. Even at a concentration of10 ppm, the current threshold limit value,the rodents developed minor lesions fromexposure.

Fire Hazard

FLAMMABLE. Flashback along vapor trail may occur. May explode if ignited in an enclosed area. Vapors are eye, skin and respiratory irritants.

Flammability and Explosibility

Extremely flammable liquified gas

Industrial uses

Dimethylamine is used as an accelerator in vulcanizing rubber, as an antiknock agent for fuels, in photography, as a plasticizer, ion exchange agent, as an acid gas absorbent, a flotation agent, a dehairing agent in the tanning of leather and in electroplating (HSDB 1989; Sax and Lewis 1987; Windholz et al 1983). Dimethylamine also serves as the base for a large number of commercial products including detergent soaps, dyes, pharmaceuticals, textile chemicals, surfactants and in the manufacture of unsymmetrical dimethylhydrazine (used in missile fuels), the solvent dimethylacetanilide and in the synthesis of dimethylformamide, one of the most commonly used organic solvents. Usage of dimethylamine in 1972 was estimated at 50% for production of dimethylformamide and dimethylacetamide (used as spinning solvents for acrylic fibers), 15% as an intermediate in the preparation of the surfactant laurel dimethylamine oxide, 15% as an intermediate for rubber chemicals (including thorium accelerators), and 20% for other applications including the production of unsymmetrical dimethylhydrazine in rocket fuels and the dimethylamine salt of 2,4-dichlorophenoxyacetic acid (HSDB 1989). U.S. production and sales of dimethylamine in 1985 was 65.9 million pounds.

Safety Profile

Poison by ingestion. Moderately toxic by inhalation and intravenous routes. Mutation data reported. An eye irritant. Corrosive to the eyes, skin, and mucous membranes. A flammable gas. When heated to decomposition it emits toxic fumes of Nx,. Incompatible with acrylddehyde, fluorine, and maleic anhydride

Potential Exposure

Mutagen.Primary Irritant. This material is used in leather tanning; asan accelerator in rubber vulcanization; in the manufactureof detergents; in drug synthesis and pesticide manufacture.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.Medical observation is recommended for 24-48 h afterbreathing overexposure, as pulmonary edema may bedelayed. As first aid for pulmonary edema, a doctor orauthorized paramedic may consider administering a corticosteroid spray.If frostbite has occurred, seek medical attention immediately; do NOT rub the affected areas or flush them withwater. In order to prevent further tissue damage, do NOTattempt to remove frozen clothing from frostbitten areas. Iffrostbite has NOT occurred, immediately and thoroughlywash contaminated skin with soap and water.

Carcinogenicity

In a 2 year inhalation study in male F344 rats exposed to 175 ppm, no evidence of carcinogenicity was observed, and in addition, despite severe tissue destruction in the anterior nose following a single 6 h exposure, the nasal lesions exhibited very little evidence of progression, even at 2 years of exposure. The authors concluded that this indicated possible regional susceptibility to DMA toxicity or a degree of adaptation by the rat to continued DMA exposure.
A detailed evaluation of mucociliary apparatus function and response to alterations of nasal structure was presented by the authors.

Source

Dimethylamine naturally occurs in soybean seeds (8 ppm), cauliflower (14 ppm), kale leaves (5.5 ppm), barleygrass seeds (1.6 ppm), tobacco leaves, hawthorne leaves, hops flower (1.4 ppm), cabbage leaves (2–2.8 ppm), corn (1–3.5 ppm), celery (5.1 ppm), grapes, grape wine, and grape juice (Duke, 1992).

Environmental Fate

Photolytic. Dimethylnitramine, nitrous acid, formaldehyde, N,N-dimethylformamide and carbon monoxide were reported as photooxidation products of dimethylamine with NOx. An additional compound was tentatively identified as tetramethylhydrazine (Tuazon et al., 1978). In the atmosphere, dimethylamine reacts with OH radicals forming formaldehyde and/or amides (Atkinson et al., 1978). The rate constant for the reaction of dimethylamine and ozone in the atmosphere is 2.61 x 10^-18 cm³/molecule?sec at 296 K (Atkinson and Carter, 1984).
Soil. After 2 d, degradation yields in an Arkport fine sandy loam (Varna, NY) and sandy soil (Lake George, NY) amended with sewage and nitrite-N were 50 and 20%, respectively. NNitrosodimethylamine was identified as the major metabolite (Greene et al., 1981). Mills and Alexander (1976) reported that N-nitrosodimethylamine also formed in soil, municipal sewage, and lake water supplemented with dimethylamine (ppm) and nitrite-N (100 ppm). They found that nitrosation occurred under nonenzymatic conditions at neutral pHs.
Photolytic. Low et al. (1991) reported that the photooxidation of aqueous secondary amine solutions by UV light in the presence of titanium dioxide resulted in the formation of ammonium and nitrate ions.
Chemical/Physical. In an aqueous solution, chloramine reacted with dimethylamine forming N-chlorodimethylamine (Isaac and Morris, 1983).
Reacts with mineral acids forming water soluble ammonium salts and ethanol (Morrison and Boyd, 1971).

Metabolism

Dimethylamine is normally present in the stomach and urine of animals and humans. The secondary amine is formed from trimethylamine (a breakdown product of dietary choline) via trimethylamine N-oxide (Zeisel et al 1985) and probably also from dietary lecithin and creatine (Lewis et al 1985). Enzymes within gut bacteria catalyze these conversions. The resulting dimethylamine is readily absorbed primarily from the small intestine, and to a much lesser extent, the stomach, and excreted in the urine (Ishiwata et al 1984; Zeisel et al 1983). Humans consuming a diet high in fish show at least a 4-fold increase in urinary dimethylamine excretion (Zeisel and Dacosta 1986).
Although dimethylamine may arise primarily from trimethylamine in a process catalyzed by bacteria, when rats were fed a commercial diet containing 23.6 p.p.m. dimethylamine, nearly 50% of the amine was recovered in the stomach with progressively declining amounts found towards lower regions of the gastrointestinal tract (Ishiwata et al 1984). Using ligated sections, the t_1/2 of dimethylamine was found to be 198 min in the stomach with the intestines and caecum varying from 8.3-31.5 min. The results indicated that dimethylamine is rapidly absorbed from the intestine and into the blood from where it disappears quickly, to be excreted predominately in the urine with a small amount excreted into the bile.
In rats fed a choline deficient diet, or rats devoid of gut bacteria, dimethylamine was still excreted in the urine (Zeisel et al 1985). This suggests that mammalian cells may possess other, as yet undefined, endogenous pathways for forming dimethylamine. The absorption, distribution and secretion of dimethylamine in the digestive tract and its biliary and urinary excretion was studied in male Wistar rats (Ishiwata et al 1984). Animals were fed diets containing 1 or 23.6 p.p.m. dimethylamine for one wk and then killed. Single i.v. doses also were administered to control and bile-duct cannulated rats and the urine collected over a 24 h period. The authors found high dimethylamine concentrations in the upper part of the gastrointestinal tract and a low concentration in the lower intestine. The half-life for injected dimethylamine was 12.5 min and excretion was primarily via the bile.
The disposition and pharmacokinetics of [¹⁴C]-dimethylamine were also studied in male Fischer 344 rats following 6 h inhalation of 10 or 175 p.p.m. of the labeled amine (McNulty and Heck 1983). At 72 h after exposure, the disposition at both doses was similar with greater than 90% of the radioactivity appearing in the urine and feces, 7-8% in various tissues and 1.5% exhaled as ¹⁴CO₂. Over 98% of the urinary radioactivity was the parent [¹⁴C]-dimethylamine. However, some formation of small quantities of dimethylamine oxidative metabolites was seen.
Much of the concern over the presence of dimethylamine in humans stems from its ability to serve as a precursor for the formation of the putative carcinogen, N-nitrosodimethylamine. Accordingly, several studies have been conducted to assess the potential for exogenously administered dimethylamine to form this nitroso compound. When dimethylamine was given intravenously to dogs and ferrets, the amine was rapidly transported from the blood into the gastric fluid, where N-nitrosodimethylamine formation can occur (Zeisel et al 1986). Nnitrosodimethylamine was formed in vitro when sodium nitrite was added to dog (Lintas et al 1982) or human gastric fluid (Zeisel et al 1988). The resulting N-nitrosamine then is rapidly absorbed from the stomach. When conventional and germfree male Wistar rats were treated with dimethylamine and sodium nitrite, severe liver necrosis was observed at 48 h only in the germfree animals (Sumi and Miyakawa 1983). This may indicate, at least in this species, that metabolism of dimethylamine by intestinal microflora may minimize nitrosamine formation. 7V-nitrosodimethylamine requires metabolic activation to form the reactive alkylating species responsible for the carcinogenic and mutagenic activity of the nitrosamine (ATSDR 1989).

storage

Dimethylamine should be stored in a cool, dry, well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA’s Hazard Communication Standard [29 CFR 1910.1200]. Containers of dimethylamine should be protected from physical damage and ignition sources, and should be stored separately from oxidizing materials, acrylaldehyde, fl uorine, maleic anhydride, chlorine, and mercury. Outside or detached storage is preferred. If stored inside, a standard flammable liquids cabinet or room should be used. Ground and bond metal containers and equipment when transferring liquids. Empty containers of dimethylamine should be handled appropriately.

Shipping

This compound requires a shipping label of“POISON GAS, FLAMMABLE GAS.” It falls in HazardClass 2.1.

Purification Methods

Dry dimethylamine by passage through a KOH-filled tower, or by standing with sodium pellets at 0o during 18hours. [Beilstein 4 IV 128.]

Incompatibilities

Dimethylamine is a medium strong base.Reacts violently with strong oxidizers; with mercury causing fire and explosion hazard. Incompatible with acids,organic anhydrides, isocyanates, vinyl acetate, acrylates,substituted allyls, alkylene oxides, epichlorohydrin, ketones,aldehydes, alcohols, glycols, phenols, cresols, caprolactumsolution. Attacks aluminum, copper, lead, tin, zinc andalloys, some plastics, rubbers, and coatings.

Precautions

During handling of dimethylamine, workers should use proper fume hoods, personal protective clothing and equipment, avoid skin contact, and use gloves, sleeves, and encapsulating suits. Dimethylamine is extremely flammable and may be ignited by heat, sparks, or open flames. Liquid dimethylamine will attack some forms of plastic, rubber, and coatings and is flammable. The vapors of dimethylamine are an explosion and poison hazard. Containers of dimethylamine may explode in the heat of a fi re and require proper disposal. Workers should use dimethylamine with adequate ventilation and containers must be kept properly closed.