What Is Dimethylamine?
Dimethylamine is a type of methylamine in which two hydrogens of ammonia are replaced by methyl groups.
It is a gaseous organic compound at room temperature and pressure that smells like fish and is also known as N-methylmethaneamine.
Uses of Dimethylamine
Dimethylamine is often used in the form of an aqueous solution dissolved in water, rather than in its gaseous state. This aqueous solution can be used as a raw material for other chemicals or used as it is.
Specifically, it is used as a raw material for N,N-dimethylformamide and dimethylacetamide. In its raw state, dimethylamine is used as a surfactant in shampoos and treatments for antistatic purposes, as a catalyst, as an insecticide and fungicide, in pharmaceuticals (antihistamines), as a vulcanization accelerator in rubber, and as a depilatory in leather.
Dimethylamine Characteristics
Dimethylamine has the structural formula (CH3)2NH, which, as can be seen from the structural formula, consists of two hydrogens of ammonia (NH3) replaced by methyl groups. It has a molecular weight of 45.08, a specific gravity of 0.66 g/ml (at 20°C), a melting point of -92.2°C, and a boiling point of 6.9°C. It is a clear, colorless gas at room temperature and pressure, or a clear, colorless liquid liquefied under pressure.
It is an extremely flammable and combustible gas, and is a recognized hazardous substance by inhalation and adhesion. Dimethylamine, like ammonia and other methylamines, is characterized by a strong fish odor, but because it is an alkaline substance, it is also known to be odorless when reacted with acidic substances. Acidic deodorizers are commonly used for amine-based odors.
Safety precautions must be taken because of the danger of producing gas when burned and of causing chemical wounds when in contact with skin or mucous membranes.
Other Information on Dimethylamine
1. How Dimethylamine Is Produced
Dimethylamine is a secondary amine with the most basic structure. In industrial production, it is produced by the dehydration reaction of ammonia and methanol using alumina or silica as a catalyst.
Synthesis of Methylamine
First, a mixture of methanol and ammonia is passed through a dehydration catalyst such as alumina or silica under pressure of 1.0~2.1 MPa at 450~500℃ to synthesize a mixture of three methylamines: monomethylamine, dimethylamine, and trimethylamine.
- Formation of monomethylamine
CH3OH + NH3 → CH3NH2 + H2O - Formation of Dimethylamine
2CH3OH + NH3 → (CH3)2NH2 + 2H2O - Formation of trimethylamine
3CH3OH + NH3 → (CH3)3NH2 + 3H2O
Separation of Dimethylamine by Dehydration and Distillation
The product is obtained by distilling under pressure to separate the raw material methanol from the water produced, then removing the azeotropic mixture of ammonia and trimethylamine to separate monomethylamine and dimethylamine.
2. Safety of Dimethylamine
Dimethylamine is sold and used either as a gas or as an aqueous solution, which differs not only in properties but also in safety and applicable regulations. Even in aqueous solution, it is highly flammable.
It may cause severe irritation to the skin and mucous membranes, and may cause chemical burns. Repeated exposure paralyzes the central nervous system, causing symptoms such as headache, elevated blood pressure, anemia, and agitation. Inhalation of high concentrations of the gas may cause pulmonary edema, and the gas is designated as a deleterious substance.
Other hazards include the following, which should be handled with care:
- Reacts violently with strong oxidizers, acids, and chlorine.
- Corrosive to aluminum, zinc, copper, and their alloys.
- May react with mercury to form explosive substances.
- Reacts with nitrite and nitric acid to form extremely toxic nitrosamines.
- Aggravates plastics, rubbers, and coatings.