Background and overview[1][2]
Methanol is the simplest alcohol, with the molecular formula CH3OH. Methanol was first separated from the distillate of dry distillation wood, so it is also called wood alcohol or wood spirit. Methanol mostly exists in nature in the form of esters or ethers, and only some leaves or fruits contain small amounts of free methanol.
Methanol is a flammable, colorless and toxic liquid; melting point -93.9°C, boiling point 65°C, relative density 0.7914 (20/4°C); pure product has a slight smell of ethanol, and crude product is pungent and unpleasant; soluble in water, Ethanol, ether, acetone, benzene and other organic solvents are less compatible with saturated hydrocarbons; they cannot form an azeotrope with water.
Methanol is flammable and explosive. During storage and transportation, it should be protected from sunlight, leakage, impact and rolling. The storage temperature should not exceed 30°C, and it cannot be stored and transported with oxidants. Operators should use personal protective equipment, paying special attention to eye protection. The workplace should have good ventilation facilities.
Chemical Applications[1]
Methanol is prone to esterification reactions with sulfuric acid and carbonic acid. It is difficult to react with hydrochloric acid at 0°C. At 160°C and under the action of sulfuric acid, metaphosphoric acid or boron trioxide, methanol can lose water and generate methyl ether. CH3-O-CH3. Methanol vapor can also lose water and generate ether through aluminum oxide and red phosphorus oxide flame retardant thorium (temperatures are 200 and ℃ respectively).
Methanol can be used as a solvent, metal halides and organic acid salts are more or less soluble in methanol, sulfates have very little solubility, and carbonates are completely insoluble in methanol. Methanol is also a raw material for making formaldehyde, formic acid and inorganic or organic acid esters.
Toxicity[3-4]
Acute poisoning is often caused by not understanding its toxicity, mistakenly using methanol as a drink instead of ethanol, or mixing methanol into drinks. Suicide and homicide using methanol are rare. The lethal dose of methanol poisoning varies greatly among individuals. Generally, 15ml can cause loss of consciousness, and 30~60ml can cause death. Methanol is different from ethanol. After entering the body through the gastrointestinal tract or respiratory tract, methanol cannot be completely oxidized in the body, but is only oxidized to formaldehyde and formic acid. Formaldehyde has a special toxic effect on retinal ganglion cells and causes optic nerve atrophy; formic acid causes acid Poisoned. Therefore, when methanol is poisoned, the more dangerous thing is the secondary toxic effects of oxidation products. In addition, the oxidation rate is slow and it has an accumulation effect, so its toxicity is higher than other alcohols. Methanol is mainly excreted slowly through the lungs, and a small amount can also be excreted by the kidneys. Symptoms of poisoning are similar to those caused by ethanol poisoning. The anesthetic effect is weak, but the local irritation effect on the mucous membrane is strong, often causing vomiting and severe abdominal pain. The most important ones are visual impairment, even blindness, and severe acidosis leading to coma.
The following measures should be implemented for acute methanol poisoning: (1) use dialysis therapy to remove absorbed methanol; (2) use glucocorticoids (such as dexamethasone) and dehydrating agents (usually hypertonic crystal dehydrating agents are used for rapid intravenous injection or intravenous infusion) to prevent and treat cerebral edema; (3) Give the patient an appropriate amount of NaHCO3 according to the blood pH value to correct acidosis. Chronic poisoning can be given general symptomatic treatment and should be separated from methanol contact.
Production method[2]
It was first isolated from the distillate of dry distillation wood. In modern industry, it is synthesized from carbon monoxide (or CO2) and hydrogen through a catalyst under high temperature and high pressure conditions, or from the direct oxidation of methane through silica gel-molybdenum oxide (forming formaldehyde at the same time).
Main reference materials
[1] Encyclopedia of China (Chemistry Volume)
[2] Chemical Dictionary
[3] Ferroalloy Dictionary
[4]Chinese Medical Encyclopedia·66 Forensic Medicine
