Methanol

Description

Methyl alcohol, also known as methanol or wood alcohol, is a clear, colorless, flammable liquid that is the simplest alcohol. The principal toxic effect is on the nervous system,particularly the retinae. Methyl alcoholis miscible in all proportions with water,ethyl alcohol, and ether. It burns with a light blue flame producing water and carbon dioxide. This vapor forms an explosive mixture(6.0 to 36.5% by volume) with air. Used to make chemicals, to remove water from automotive and aviation fuels, as a solvent for paints and plastics, and as an ingredient in a wide variety of products.

Chemical properties

Methanol is a clear, water-white liquid with a mild odor at ambient temperatures.The air odor threshold for methanol has been reported as 100 ppm . Others have reported that 2000 or 5900 ppm methanol is barely detectable .

History

It was first isolated in 1661 by the Irish chemist Robert Boyle (1627–1691) who prepared it by the destructive distillation of boxwood, giving it the name spirit of box, and the name wood alcohol is still used for methyl alcohol. Methyl alcohol is also called pyroxylic spirit; pyroxylic is a general term meaning distilled from wood and indicates that methyl alcohol is formed during pyrolysis of wood. The common name was derived in the mid-1800s. The name methyl denotes the single carbon alkane methane in which a hydrogen atom has been removed to give the methyl radical. The word alcohol is derived from Arabic al kuhul.

The Uses of Methanol

Methyl alcohol is an important inexpensive raw material that is synthetically produced for the organic chemical industry. Nearly half of the methyl alcohol manufactured is used in the production of formaldehyde. Other uses of methyl alcohol are as an antifreeze and fuel for automobiles and as an intermediate in the production of synthetic protein. It is used in the production offormaldehyde, acetic acid, methyl tert-butylether, and many chemical intermediates; asan octane improver (in oxinol); and as apossible alternative to diesel fuel; being anexcellent polar solvent, it is widely used as acommon laboratory chemical and as a methylating reagent.

Definition

ChEBI: Methanol is the primary alcohol that is the simplest aliphatic alcohol, comprising a methyl and an alcohol group. It has a role as an amphiprotic solvent, a fuel, a human metabolite, an Escherichia coli metabolite, a mouse metabolite and a Mycoplasma genitalium metabolite. It is an alkyl alcohol, a one-carbon compound, a volatile organic compound and a primary alcohol. It is a conjugate acid of a methoxide.

Production Methods

Modern industrial-scale methanol production is exclusively based on synthesis from pressurized mixtures of hydrogen, carbon monoxide, and carbon dioxide gases in the presence of catalysts. Based on production volume, methanol has become one of the largest commodity chemicals produced in the world.

World Health Organization (WHO)

Methanol has been subjected to abuse by consumption as a substitute for ethanol. Its toxic metabolites cause irreversible blindness and severe metabolic acidosis, and are ultimately fatal. Methanol continues to be used as an industrial solvent.

Reactivity Profile

Methanol reacts violently with acetyl bromide [Merck 11th ed. 1989]. Mixtures with concentrated sulfuric acid and concentrated hydrogen peroxide can cause explosions. Reacts with hypochlorous acid either in water solution or mixed water/carbon tetrachloride solution to give methyl hypochlorite, which decomposes in the cold and may explode on exposure to sunlight or heat. Gives the same product with chlorine. Can react explosively with isocyanates under basic conditions. The presence of an inert solvent mitigates this reaction [Wischmeyer 1969]. A violent exothermic reaction occurred between methyl alcohol and bromine in a mixing cylinder [MCA Case History 1863. 1972]. A flask of anhydrous lead perchlorate dissolved in Methanol exploded when Methanol was disturbed [J. Am. Chem. Soc. 52:2391. 1930]. P4O6 reacts violently with Methanol. (Thorpe, T. E. et al., J. Chem. Soc., 1890, 57, 569-573). Ethanol or Methanol can ignite on contact with a platinum-black catalyst. (Urben 1794).

Hazard

Flammable, dangerous fire risk. Explosive limits in air 6–36.5% by volume. Toxic by ingestion (causes blindness). Headache, eye damage, dizziness, and nausea.

Safety Profile

A human poison by ingestion. Poison experimentally by skin contact. Moderately toxic experimentally by intravenous and intraperitoneal routes. Mildly toxic by inhalation. Human systemic effects: changes in circulation, cough, dyspnea, headache, lachrymation, nausea or vomiting, optic nerve neuropathy, respiratory effects, visual field changes. An experimental teratogen. Experimental reproductive effects. An eye and skin irritant. Human mutation data reported. A narcotic. Its main toxic effect is exerted upon the nervous system, particularly the optic nerves and possibly the retinae. The condtion can progress to permanent blindness. Once absorbed, methanol is only very slowly eliminated. Coma resulting from massive exposures may last as long as 2-4 days. In the body, the products formed by its oxidation are formaldehyde and formic acid, both of which are toxic. Because of the slow elimination, methanol should be regarded as a cumulative poison. Though single exposures to fumes may cause no harmful effect, daily exposure may result in the accumulation of sufficient methanol in the body to cause illness. Death from ingestion of less than 30 mL has been reported. A common air contaminant. Flammable liquid. Dangerous fire hazard when exposed to heat, flame, or oxidlzers. Explosive in the form of vapor when exposed to heat or flame. Explosive reaction with chloroform + sodium methoxide, diethyl zinc. Violent reaction with alkyl aluminum salts, acetyl bromide, chloroform + sodlum hydroxide, CrO3, cyanuric chloride, (I + ethanol + HgO), Pb(ClO4)2, HClO4, P2O3, (KOH + CHCb), nitric acid. Incompatible with berylhum dihydride, metals (e.g., potassium, magnesium), oxidants (e.g., barium perchlorate, bromine, sodium hypochlorite, chlorine, hydrogen peroxide), potassium tert-butoxide, carbon tetrachloride + metals (e.g., aluminum, magnesium, zinc), dlchloromethane. Dangerous; can react vigorously with oxidizing materials. To fight fire, use alcohol foam. When heated to decomposition it emits acrid smoke and irritating fumes.

Potential Exposure

Drug,Mutagen; Reproductive Effector; Human Data; PrimaryIrritant. Methyl alcohol is used as a starting material inorganic synthesis of chemicals, such as formaldehyde,methacrylates, methyl amines, methyl halides, ethylene glycol, and pesticides, and as an industrial solvent for inks, resins, adhesives, and dyes. It is an ingredient in paint and varnish removers, cleaning and dewaxing preparations, spirit duplicating fluids, embalming fluids, antifreeze mixtures, and enamels, and is used in the manufacture of photographic film, plastics, celluloid, textile soaps, wood stains, coated fabrics, shatterproof glass, paper coating, waterproofing formulations, artificial leather, and synthetic indigo and other dyes. It has also been used as an extractant in many other processes, an antidetonant fuel-injection fluid for aircraft, a rubber accelerator, and a denaturant for ethyl alcohol.

First aid

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and induce vomiting. Do not make an unconscious person vomit.

Source

Methanol occurs naturally in small-flowered oregano (5 to 45 ppm) (Baser et al., 1991), Guveyoto shoots (700 ppb) (Baser et al., 1992), orange juice (0.8 to 80 ppm), onion bulbs, pineapples, black currant, spearmint, apples, jimsonweed leaves, soybean plants, wild parsnip, blackwood, soursop, cauliflower, caraway, petitgrain, bay leaves, tomatoes, parsley leaves, and geraniums (Duke, 1992).
Methanol may enter the environment from methanol spills because it is used in formaldehyde solutions to prevent polymerization (Worthing and Hance, 1991).

Toxicity evaluation

The toxic properties of methanol are the result of accumulation of the formate intermediate in the blood and tissues of exposed individuals. Formate accumulation produces metabolic acidosis leading to the characteristic ocular toxicity (blindness) observed in human methanol poisonings.
Humans and primates appear particularly sensitive to methanol toxicity when compared to rats. This is attributed to the slower rate of conversion in humans of the formate metabolite via tetrahydrofolate. This step in methanol metabolism occurs in rats at a rate ～2.5 times that observed in humans.
Formate appears to directly affect the retina and optic nerve by acting as a mitochondrial toxin. It is believed that formate acts as a metabolic poison by inhibiting cytochrome oxidase activity. The cells of the optic nerve have low reserves of cytochrome oxidase and thus may be particularly sensitive to formate-induced metabolic inhibition.

Incompatibilities

Methanol reacts violently with strong oxidizers, causing a fire and explosion hazard.

Waste Disposal

Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal. Incineration