Acetone

Acetone[1]
IUPAC name propanone
Other names β-ketopropane, dimethyl ketone, dimethylformaldehyde, DMK, propanone, 2-propanone, propan-2-one
Identifiers
CAS number	67-64-1 Y
PubChem	180
ChemSpider	175
EC-number	200-662-2
ChEBI	15347
RTECS number	AL31500000
SMILES O=C(C)C
InChI InChI=1/C3H6O/c1-3(2)4/h1-2H3 Key: CSCPPACGZOOCGX-UHFFFAOYAF
Properties
Molecular formula	C3H6O
Molar mass	58.08 g mol−1
Appearance	Colorless liquid (white snow-like form when solid)
Density	0.7925 g/cm3
Melting point	−94.9 °C, 178 K, -139 °F
Boiling point	56.53 °C, 330 K, 134 °F
Solubility in water	miscible
Acidity (pKa)	24.2
Refractive index (nD)	1.35900 (20 °C)
Viscosity	0.3075 cP
Structure
Molecular shape	trigonal planar at C=O
Dipole moment	2.91 D
Hazards
EU classification	F Xi
R-phrases	R11, R36, R66, R67
S-phrases	(S2), S9, S16, S26
NFPA 704	3 1 0
Flash point	−17 °C
Autoignition temperature	465 °C
Explosive limits	4.0–57.0
Threshold Limit Value	500 ppm (TWA), 750 ppm (STEL)
LD50	>2000 mg/kg, oral (rat)
Related compounds
Related solvents	Water Ethanol Isopropanol Toluene
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Acetone is the organic compound with the formula (CH₃)₂CO. This colorless, mobile, flammable liquid is the simplest example of the ketones. Acetone is miscible with water and serves as an important solvent in its own right, typically as the solvent of choice for cleaning purposes in the laboratory. More than 3 million tonnes are produced annually, mainly as a precursor to polymers.^[2] Familiar household uses of acetone are as the active ingredient in nail polish remover and as paint thinner and sanitary cleaner/nail polish remover base. It is a common building block in organic chemistry.

Acetone is naturally produced and disposed of in the human body as a result of normal metabolic processes. Reproductive toxicity tests show that it has low potential to cause reproductive problems. In fact, the body naturally increases the level of acetone in pregnant women, nursing mothers and children because their higher energy requirements lead to higher levels of acetone production. The medical community is now using ketogenic diets that increase acetone in the body to reduce epileptic attacks in infants and children who suffer from recalcitrant refractory epilepsy.

Production

Acetone is produced directly or indirectly from propylene. Most commonly, in the cumene process, benzene is alkylated with propene and the resulting cumene (isopropylbenzene) is oxidized to give phenol and acetone:

C₆H₅CH(CH₃)₂ + O₂ → C₆H₅OH + (CH₃)₂CO

This conversion entails the intermediacy of cumene hydroperoxide, C₆H₅C(OOH)(CH₃)₂.

Acetone is also produced by the direct oxidation of propene with a Pd(II)/Cu(II) catalyst, akin to the Wacker process.

Older production methods

Previously, acetone was produced by the dry distillation of acetates, for example calcium acetate. During World War I acetone was produced via bacterial fermentation, as developed by Chaim Weizmann (later the first president of Israel) in order to help the British war effort.^[2] This Acetone Butanol Ethanol process was abandoned due to the small yields.^[2]

Biosynthesis

Small amounts of acetone are produced in the body by the decarboxylation of ketone bodies.

Uses

About half of the world's production of acetone is consumed as a precursor to methyl methacrylate. This application begins with the initial conversion of acetone to its cyanohydrin:

(CH₃)₂CO + HCN → (CH₃)₂C(OH)CN

In a subsequent step, the nitrile is hydrolyzed to the unsaturated amide, which is esterified:

(CH₃)₂C(OH)CN + CH₃OH → CH₂=(CH₃)CCO₂CH₃ + NH₃

The second major use of acetone entails its condensation with phenol to give bisphenol A:

(CH₃)₂CO + 2 C₆H₅OH → (CH₃)₂C(C₆H₄OH)₂ + H₂O

Bisphenol-A is a component of many polymers such as polycarbonates, polyurethanes, and epoxy resins.

Combustion

(CH₃)₂CO + 4 O₂ → 3 CO₂ + 3 H₂O

As a solvent

Acetone is a good solvent for most plastics and synthetic fibres including those used in laboratory bottles made of polystyrene, polycarbonate and some types of polypropylene.^[3] It is ideal for thinning fiberglass resin, cleaning fiberglass tools and dissolving two-part epoxies and superglue before hardening. It is used as a volatile component of some paints and varnishes. As a heavy-duty degreaser, it is useful in the preparation of metal prior to painting; it also thins polyester resins, vinyl and adhesives.

Many millions of kilograms of acetone are consumed in the production of the solvents methyl isobutyl alcohol and methyl isobutyl ketone. These products arise via an initial aldol condensation to give diacetone alcohol.^[2]

2 (CH₃)₂CO → (CH₃)₂C(OH)CH₂C(O)CH₃

Acetone is used as a solvent by the pharmaceutical industry and as a denaturation agent in denatured alcohol.^[4] Acetone is also present as an excipient in some pharmaceutical products.^[5]

Storage of acetylene

Although flammable itself, acetone is also used extensively as a solvent for the safe transporting and storing of acetylene, which cannot be safely pressurized as a pure compound. 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.^[6][7]

Medical and cosmetic uses

Acetone is used in a variety of general medical and cosmetic applications and is also listed as a component in food additives and food packaging.

Acetone is commonly used in the skin rejuvenation process in medical offices and medical spas. Since the days of ancient Egypt, people have been using chemexfoliation methods, also known as chemical peeling, to rejuvenate skin. Common agents used today for chemical peels are salicylic acid, glycolic acid, 30% salicylic acid in ethanol, and trichloroacetic acid (TCA). Prior to chemexfoliation, the skin should be cleaned properly and excess fat removed. This process is known as defatting. Acetone, Septisol, or a combination of these agents is commonly used in this process.

Laboratory uses

In the laboratory, acetone is used as a polar aprotic solvent in a variety of organic reactions, such as S_N2 reactions. The use of acetone solvent is also critical for the Jones oxidation. It is a common solvent for rinsing laboratory glassware because of its low cost and volatility, however, it does not form an azeotrope with water ^{[8] [9]}. Despite its common use as a supposed drying agent, it is not effective except by bulk displacement and dilution. Acetone can be cooled with dry ice to −78 °C without freezing; acetone/dry ice baths are commonly used to conduct reactions at low temperatures. Acetone is fluorescent under ultraviolet light, and its vapor may be used as a fluorescent tracer in fluid flow experiments.^[10]

Domestic and other niche uses

Acetone is often the primary component in cleaning agents such as nail polish remover. Ethyl acetate, another organic solvent, is sometimes used as well. Acetone is a component of superglue remover and it easily removes residues from glass and porcelain.

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 transfers to the destination surface.

Make-up artists use acetone to remove skin adhesive from the netting of wigs and moustaches by immersing the item in an acetone bath, then removing the softened glue residue with a stiff brush.

Some automotive enthusiasts add acetone at around 1 part in 500 to their fuel, following claims of improvement in fuel economy and engine life.^[11] Systematic testing has determined that acetone has no measurable effect on fuel economy or may in fact reduce engine life by adversely affecting fuel system parts.^[12][13]

Mapping of industrial releases in the United States

One tool that maps releases of acetone [1] [2] to particular locations in the United States^[14] and also provides additional information about such releases is TOXMAP. TOXMAP is a Geographic Information System (GIS) from the Division of Specialized Information Services of the United States National Library of Medicine (NLM) that uses maps of the United States to help users visually explore data from the United States Environmental Protection Agency's (EPA) Toxics Release Inventory and Superfund Basic Research Programs. TOXMAP is a resource funded by the US Federal Government. TOXMAP's chemical and environmental health information is taken from NLM's Toxicology Data Network (TOXNET)^[15] and PubMed, and from other authoritative sources.

Safety

Flammability

The most common hazard associated with acetone is its extreme flammability. It auto-ignites at a temperature of 465 °C (869 °F). At temperatures greater than acetone's flash point of −20 °C (−4 °F), 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 sources and flash back. Static discharge may also ignite acetone vapors.^[16]

Health Information

Acetone has been studied extensively and is generally recognized to have low acute and chronic toxicity if ingested and/or inhaled. Inhalation of high concentrations (around 9200 ppm) in the air caused irritation of the throat in humans in as little as 5 minutes. Inhalation of concentrations of 1000 ppm caused irritation of the eye and throat in less than 1 hour; however, Inhalation 500 ppm of acetone in the air caused no symptoms of irritation in humans even after 2 hours of exposure. Acetone is not currently regarded as a carcinogen, a mutagenic chemical or a concern for chronic neurotoxicity effects.

Acetone can be found as an ingredient in a variety of consumer products ranging from cosmetics to processed and unprocessed foods. Acetone has been rated as a GRAS (Generally Recognized as Safe) substance when present in beverages, baked goods, desserts, and preserves at concentrations ranging from 5 to 8 mg/L. Additionally, a joint U.S-European study found that acetone’s "health hazards are slight."

An extensive study was also conducted on "reasonably anticipated children’s exposures to acetone" from commonly found items such as the solvent in nail tip remover, nail polish remover, spray paint and spot remover. The conclusion was that acetone exposure from a child’s environment and from consumer products is unlikely to pose significant health risks. It was determined that 90 percent of acetone found in children was naturally produced in their bodies. The rest came primarily from natural food sources, such as onions, grapes, cauliflower, tomatoes, milk, cheese, beans and peas, as well as from mother’s milk.

Toxicology

Acetone is believed to exhibit only slight toxicity in normal use, and there is no strong evidence of chronic health effects if basic precautions are followed.^[17]

At very high vapor concentrations, acetone is irritating and, like many other solvents, may depress the central nervous system. It is also a severe irritant on contact with eyes, and a potential pulmonary aspiration risk. In one documented case, ingestion of a substantial amount of acetone led to systemic toxicity, although the patient eventually fully recovered.^[18] Some sources estimate LD₅₀ for human ingestion at 1.159 g/kg; LD₅₀ inhalation by mice is given as 44 g/m³, over 4 hours.^[19]

Acetone has been shown to have anticonvulsant effects in animal models of epilepsy, in the absence of toxicity, when administered in millimolar concentrations.^[20] 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.^[20]

• EPA EPCRA Delisting (1995). EPA removed acetone from the list of “toxic chemicals” maintained under Section 313 of the Emergency Planning and Community Right to Know Act (EPCRA). In making that decision, EPA conducted an extensive review of the available toxicity data on acetone and found that acetone “exhibits acute toxicity only at levels that greatly exceed releases and resultant exposures,” and further that acetone “exhibits low toxicity in chronic studies.”

• Genotoxicity. Acetone has been tested in more than two dozen in vitro and in vivo assays.

These studies indicate that acetone is not genotoxic.

• Carcinogenicity. EPA in 1995 concluded, “There is currently no evidence to suggest a concern for carcinogenicity.”(EPCRA Review, described in Section 3.3). NTP scientists have recommended against chronic toxicity/carcinogenicity testing of acetone because “the prechronic studies only demonstrated a very mild toxic response at very high doses in rodents.”

• Neurotoxicity and Developmental Neurotoxicity. The neurotoxic potential of both acetone and isopropanol, the metabolic precursor of acetone, have been extensively studied. These studies demonstrate that although exposure to high doses of acetone may cause transient central nervous system effects, acetone is not a neurotoxicant. A guideline developmental neurotoxicity study has been conducted with isopropanol, and no developmental neurotoxic effects were identified, even at the highest dose tested. (SIAR, pp. 1, 25, 31).

• Environmental. When the EPA exempted acetone from regulation as a volatile organic compound (VOC) in 1995, EPA stated that this exemption would “contribute to the achievement of several important environmental goals and would support EPA’s pollution prevention efforts.” 60 Fed. Reg. 31,634 (June 16, 1995). 60 Fed. Reg. 31,634 (June 16, 1995). EPA noted that acetone could be used “as a substitute for several compounds that are listed as hazardous air pollutants (HAP) under section 112 of the [Clean Air] Act.

Environmental effects

Acetone evaporates rapidly, even from water and soil. Once in the atmosphere, it is degraded by UV light with a 22-day half-life. Acetone dissipates slowly in soil, animals, or waterways since it is sometimes consumed by microorganisms,^[21] but it is a significant groundwater contaminant due to its high solubility in water. The LD₅₀ of acetone for fish is 8.3 g/l of water (or about 0.8%) over 96 hours, and its environmental half-life is about 1 to 10 days. Acetone may pose a significant risk of oxygen depletion in aquatic systems due to the microbial activity consuming it.^[22]

Acetone peroxide

When oxidized, acetone forms acetone peroxide as a byproduct, which is a highly unstable compound. It may be formed accidentally, e.g. when waste hydrogen peroxide is poured into waste solvent containing acetone. Acetone peroxide is more than ten times as sensitive to friction and shock as nitroglycerin. Due to its instability, it is rarely used, despite its easy chemical synthesis.

References

External links

• International Chemical Safety Card 0087
• National Pollutant Inventory: Acetone
• NIOSH Pocket Guide to Chemical Hazards
• Hazardous substances databank entry at the national library of medicine
• SIDS Initial Assessment Report for Acetone from the Organisation for Economic Co-operation and Development (OECD)
• Calculation of vapor pressure, liquid density, dynamic liquid viscosity, surface tension of acetone
• Fisher Chemical MSDS