N. N-dimethylformamide, a colourless and transparent liquid, is not only a widely used chemical raw material but also an excellent solvent.
It is a toxic chemical that requires special attention during operation and storage. Toxicity can be divided into three types according to different severity: 1. Acute toxicity: LD50: 400mg / kg (oral to rats); 5000mg / kg (rabbit percutaneous). LC50: 9400mg / m3, 2h (inhaled by mice). When people inhale 30 ~ 60ppm, they have gastrointestinal symptoms, abnormal liver function, jaundice, increased urobilinogen and proteinuria; When people inhale 10-20ppm (sometimes 30ppm), they have a headache, loss of appetite, nausea, normal liver function and ECG. 2. Irritation: rabbit eye: 100%, severe irritation (rinse with water) 3. Subacute and chronic toxicity: rats inhaled 2500mg / m 3,6h / D, 5 days, 80% died, liver and lung lesions; Human inhalation 5.1 ~ 49mg / m3 × In 3 years, neurasthenia syndrome, low blood pressure and changes in liver function occurred.
Metabolic uses: after being absorbed in various ways, N, N-dimethylformamide (DMF) is mainly metabolized in the liver and excreted rapidly. The main target organ is the liver, and there is also some damage to the kidney. Demethylation is primarily carried out by microsomal mixed functional oxidase in the liver, and one methyl is removed. The metabolites are dimethylformamide and formamide, which are metabolized rapidly; Formamide stays in the blood for a bit more extended and then is metabolized into formic acid and ammonia. Part of dimethylformamide is excreted from urine and exhalation as a prototype.
There are many aspects of health hazards, especially the impact on human organs is more obvious: irritating to eyes, skin and respiratory tract. Steam can cause mild and moderate irritation of the eyes and upper respiratory tract. Polluting the skin can cause light and heavy burns, wrinkled skin, white complexion accompanied by burning pain. In severe cases, the skin can swell and burn violently. Eye pollution causes burning pain, tears and conjunctival congestion; Severe cases can cause corneal necrosis. Gastrointestinal symptoms: patients often have a loss of appetite, nausea, vomiting, abdominal discomfort and constipation, and a few instances have middle and upper abdominal pain. Liver: liver damage is often prominent in acute poisoning. The patient has apparent fatigue, swelling and pain in the right upper abdomen, discomfort, jaundice, gradual enlargement of the liver and tenderness. Routine liver function examination shows abnormalities in which the increase of serum aminotransferase is more prominent. The lesion is generally not severe, which can be gradually reduced after treatment, and the condition can be completely recovered within a few weeks. Severe acute poisoning: it is characterized by severe toxic liver disease. Occupational poisoning is rare. Those exposed to high concentrations, especially those with severe skin pollution and not thoroughly washed in time, should be vigilant against severe poisoning. Therefore, in regular operation, operators must wear chemical protective clothing for operation.
Since the first synthesis of dimethylformamide by the reaction of formic acid and dimethylamine in 1899, synthesizing dimethylformamide from different raw materials has been developed. Therefore, researchers have tried other synthetic methods in the laboratory. The synthetic methods of N, N-dimethylformamide are as follows: 1. Methyl formate dimethylamine method: methyl formate is esterified from formic acid and methanol to form methyl formate and then reacted with dimethylamine to form dimethylformamide in the gas phase. Then methanol and unreacted methyl formate are recovered by distillation, and the finished product is prepared by vacuum distillation. 2. Dimethylamine carbon monoxide method: it is obtained by the direct reaction of dimethylamine and carbon monoxide under the action of sodium methoxide. The reaction conditions are 1.5-2.5mpa and 110-150 ℃. The crude product is distilled to obtain the finished product. 3. Dimethylamine and carbon dioxide are synthesized under pressure under the catalysis of sodium methoxide or prepared by the gas phase reaction of N. N-dimethylformamide and methyl formate or by the reaction of dimethylamine and Trichloroacetaldehyde.