Dimethylamine 二甲胺 Dimethylamine

Dimethylamine

Detailed introduction of dimethylamine

Basic information

Chinese name: 二甲胺

English name: Dimethylamine

Alias: N-methylmethylamine, aminodimethane

CAS number: 124-40-3

Chemical formula: C₂H₇N or (CH₃)₂NH

Molar mass: 45.08g/mol

physical properties

• Appearance: colorless gas (at normal temperature) or liquid, with a fishy smell at low concentrations and ammonia smell at high concentrations.

• Density: 0.68 (relative density); 1.6 (relative vapor density)

• Melting point: -92.2℃

• Boiling point: 7.0℃

• Solubility: Easily soluble in water, ethanol, ether

• Vapor pressure: 203kPa (25℃)

• Flash point: -20°C (closed cup)

• Explosion limit: 2.8%~14.4% (volume) in air

• Autoignition temperature: 400℃

chemical properties

1. Alkaline: The nitrogen atom provides a lone pair of electrons and is alkaline, and can form salts with inorganic acids (such as dimethylamine hydrochloride)

2. Alkylation reaction: reacts with alkyl halide or alcohol, and the hydrogen atom on the nitrogen is replaced by an alkyl group

3. Acylation reaction: react with acid chloride or acid anhydride to form amide

4. Nitrosation reaction: reacts with nitrous acid to generate N-nitrosodimethylamine (yellow oil beads)

5. Thermal stability: thermal cracking at 420~440℃ generates methylamine, methane and hydrogen

Preparation method

Through the reaction of methanol and ammonia at high temperature (300-400℃) and high pressure (2-5MPa) using activated alumina as a catalyst, a mixture of monomethylamine, dimethylamine and trimethylamine is generated, and then the pure product is obtained by distillation and separation. In industry, it is commonly stored and transported in the form of 40% aqueous solution.

Main purpose

Industrial field

• Chemical raw materials: production of dimethylformamide (DMF), dimethylacetamide (DMAC) and other solvents

• Rubber industry: vulcanization accelerator (such as sodium dimethyldithiocarbamate), latex stabilizer

• Surfactants: synthetic dodecyldimethylamine oxide, etc.

Medical field

• Synthesis of drug intermediates such as antihistamines (diphenhydramine) and antibiotics (minocycline)

agricultural field

• Preparation of fungicides (thiram, thiram), insecticides (pyrimethuron, thiram), herbicides (trimethuron, isoproturon)

Other applications

• Leather hair remover, petroleum industry corrosion inhibitor, water treatment pH adjuster, rocket propellant raw material

Safety and Risk

health hazards

• Inhalation: irritates the respiratory tract, high concentrations can cause pulmonary edema

• Skin contact: Liquid dimethylamine can cause necrosis and burns

• Eye contact: Causes corneal damage, opacity, and severe blindness.

• Acute toxicity: Rat oral LD₅₀ 698mg/kg, inhalation LC₅₀ 4540ppm (2h)

Explosion risk

• Extremely flammable gas, which forms an explosive mixture when mixed with air. It is easy to explode when exposed to open flames or high temperatures.

• The gas is heavier than air and can spread along the ground and backfire when encountering a fire source

protective measures

• Respiratory system: Wear a self-priming filter respirator (full face mask)

• Body protection: Wear anti-static overalls and rubber gloves

• Storage requirements: cool and ventilated warehouse, away from fire sources and oxidants, the storage temperature does not exceed 30℃

Emergency treatment

• Leakage: Cut off the air source, dilute with spray water, and build a dike to contain the leakage.

• Skin contact: rinse immediately with plenty of running water for 15 minutes

• Eye contact: Lift your eyelids, rinse with saline for 15 minutes and seek medical advice.

• Inhalation: Move to fresh air, give oxygen or artificial respiration if necessary

Regulations and Standards

• China occupational exposure limits: PC-TWA 5mg/m³, PC-STEL 10mg/m³

• UN number: 1032 (liquefied gas)

• Classification of dangerous goods: flammable gases (category 1), pressurized gases

Industrial Product Specifications

• Common form: 40% aqueous solution (easy to transport and store)

• Purity: industrial grade ≥99.5%, reagent grade ≥99.9%

• Packaging: pressure-resistant steel cylinder (waterless), tanker or iron drum (aqueous solution)

Note: Safety regulations must be strictly followed when operating dimethylamine, avoid contact with strong acids and strong oxidants, and prevent leakage, combustion and explosion accidents.