标题: Acetone [打印本页] 作者: wyj7506 时间: 2008-7-23 21:38 标题: Acetone Acetone (also known as propanone, dimethyl ketone, 2-propanone, propan-2-one and β-ketopropane) is a colorless, mobile, flammable liquid. It is the simplest example of the ketones. Acetone is miscible with water, ethanol, ether, etc., and itself serves as an important solvent. The most familiar household uses of acetone are as the active ingredient in nail polish remover and paint thinner. Acetone is also used to make plastic, fibers, drugs, and other chemicals. In addition to being manufactured as a chemical, acetone is also found naturally in the environment, including in small amounts in the human body.
Production
Acetone is produced primarily in the cumene process. Previously, acetone was produced by the dry distillation of acetates, for example calcium acetate. During World War I a new process of producing acetone through bacterial fermentation was developed by Chaim Weizmann, later the first president of Israel, in order to help the British war effort. This Acetone Butanol Ethanol process was abandoned due to the small yield of Acetone Butanol compared to the organic waste.
Biosynthesis
See also: ketosis
Small amounts of acetone are produced in the body by the decarboxylation of ketone bodies.
Uses
Cleaning fluid
Acetone is often the primary (or only) component in nail polish remover. Ethyl acetate, another organic solvent, is sometimes used as well. Acetone is also used as a superglue remover. It can be used for thinning and cleaning fiberglass resins and epoxies. It is a strong solvent for most plastics and synthetic fibres.
It is ideal for thinning fiberglass resin, cleaning fiberglass tools and dissolving two-part epoxies and superglue before hardening. A heavy-duty degreaser, it is useful in the preparation of metal prior to painting; it also thins polyester resins, vinyl and adhesives. It easily removes residues from glass and porcelain. In biological research contexts, buffers that contain acetone (such as citrate-buffered formalin) use the acetone to lyse cells for further experimentation.
Additionally, acetone is extremely effective when used as a cleaning agent when dealing with permanent markers.
Solvent
Acetone can also dissolve many plastics, including those used in Nalgene bottles made of polystyrene, polycarbonate and some types of polypropylene.
In the laboratory, acetone is used as a polar aprotic solvent in a variety of organic reactions, such as SN2 reactions. The use of acetone solvent is also critical for the successful Jones oxidation. Technical grade acetone is inexpensive. Because of acetone's medium polarity, it dissolves a wide range of compounds. Thus, it is commonly loaded into squeeze bottles and used as a general solvent in rinsing laboratory glassware.
Acetone is also used extensively for the safe transporting and storing of acetylene. Vessels containing a porous material are first filled with acetone followed by acetylene, which dissolves into the acetone. One liter of acetone can dissolve around 250 liters of acetylene.
Feedstock
An important industrial use for acetone involves its reaction with phenol for the manufacture of bisphenol A. Bisphenol A is an important component of many polymers such as polycarbonates, polyurethanes and epoxy resins. Acetone has also been used in the manufacture of cordite.
Automotive fuel additive
Some automotive enthusiasts add acetone at around 1 part in 500 to their fuel, following claims of dramatic improvement in fuel economy and engine life. This practice is controversial as the body of systematic testing shows that acetone has no measurable effect or may in fact reduce engine life by adversely affecting fuel system parts.Debates on this subject and the perrenial claims of a "Big Oil" cover-up intensified when the practice was addressed on the popular American TV show MythBusters in 2006, and shown to have negative effect in the televised fuel economy test.[8].
Other uses
Acetone is also used as a drying agent, due to the readiness with which it mixes with water, and its volatility.
It can be used as an artistic agent; when rubbed on the back of a laser print or photocopy placed face-down on another surface and burnished firmly, the toner of the image is allowed to transfer to the destination surface.
Though flammable itself, liquid acetone is often used in the mining industry to safely store and transport the highly explosive and flammable acetylene. In an enclosed vessel, one liter of acetone can dissolve 250 liters of acetylene, under a pressure of 10 atmospheres.
Safety
Flammability
The most common hazard associated with acetone is its extreme flammability. It auto ignites at a temperature of 465C (869F). At temperatures greater than acetone's flash point of -20C (-4F), air mixtures of between 2.5% and 12.8% acetone, by volume, may explode or cause a flash fire. Vapors can flow along surfaces to distant ignition source and flash back. Static discharge may also ignite acetone fires.
Toxicity
Acetone may be harmful by inhalation, ingestion, or skin absorbtion, but fatalities only occur with larger quantities:
LD50 ingested by humans: 1.159 g/kg
LD50 inhalation by mice: 44g per cubic meter, over 4 hours.
Acetone peroxide
Main article: acetone peroxide
When oxidized, acetone forms acetone peroxide as a by-product, which is a highly unstable compound. It may be formed accidentally, e.g. when waste hydrogen peroxide is poured into a carboxy-containing waste acetone solvent. Acetone peroxide is more than ten times as friction and shock sensitive as nitroglycerin. Due to its instability, it is rarely used, despite its easy chemical synthesis.
Toxicology
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Acetone is an irritant and inhalation may lead to hepatotoxic effects (causing liver damage). The vapors should be avoided. In no circumstance should it be consumed directly or indirectly.Always use goggles when handling acetone; it can cause permanent eye damage (corneal clouding).
Small amounts of acetone are metabolically produced in the body, mainly from fat. In humans, fasting significantly increases its endogenous production (see ketosis). Acetone can be elevated in diabetes. Contamination of water, food (e.g. milk), or the air (acetone is volatile) can lead to chronic exposure to acetone. A number of acute poisoning cases have been described. Relatively speaking, acetone is not a very toxic compound; it can, however, damage the mucosa of the mouth and can irritate and damage skin. Accidental intake of large amounts of acetone may lead to unconsciousness and death.
The effects of long-term exposure to acetone are known mostly from animal studies. Kidney, liver, and nerve damage, increased birth defects, and lowered reproduction ability of males (only) occurred in animals exposed long-term. It is not known if these same effects would be exhibited in humans. Pregnant women should avoid contact with acetone and acetone fumes in order to avoid the possibility of birth defects, including brain damage.
Interestingly, acetone has been shown to have anticonvulsant effects in animal models of epilepsy, in the absence of toxicity, when administered in millimolar concentrations.[13] It has been hypothesized that the high fat low carbohydrate ketogenic diet used clinically to control drug-resistant epilepsy in children works by elevating acetone in the brain.
Environmental Effects
Acetone evaporates rapidly, even from water and soil. Once in the atmosphere, it degraded by UV light with a 22-day half-life. Acetone does not build up in soil, animals, or waterways since it is consumed by microorganisms. LD50 in fish is 8.3g/l of water (or about 0.8%) over 96 hours. Environmental half-life is about 1 to 10 days. But acetone may pose a significant risk of oxygen depletion in aquatic systems due to the microbial activity consuming it.
CERCLA requires reporting a spill of 5000 lbs or more.