Acetone (2-propanone ordimethyl ketone) is anorganic compound with theformula(CH3)2CO.[22] It is the simplest and smallestketone (R−C(=O)−R'). It is a colorless, highlyvolatile, andflammable liquid with a characteristic pungent odour, very reminiscent of the smell ofpear drops.
From the 17th century, and before modern developments inorganic chemistry nomenclature, acetone was given many different names. They included "spirit of Saturn", which was given when it was thought to be a compound oflead and, later, "pyro-acetic spirit" and "pyro-acetic ester".[6]
Prior to the name "acetone" being coined byFrench chemists (seebelow), it was named "mesit" (from the Greek μεσίτης, meaning mediator) byCarl Reichenbach, who also claimed thatmethyl alcohol consisted of mesit andethyl alcohol.[27][6] Names derived from mesit includemesitylene andmesityl oxide which were first synthesised from acetone.
Unlike many compounds with theacet- prefix which have a 2-carbon chain, acetone has a 3-carbon chain. That has caused confusion because there cannot be aketone with 2 carbons. The prefix refers to acetone's relation tovinegar (acetum inLatin, also the source of the words "acid" and "acetic"), rather than its chemical structure.[28]
In 2010, the worldwide production capacity for acetone was estimated at 6.7 million tonnes per year.[40] With 1.56 million tonnes per year, theUnited States had the highest production capacity,[41] followed byTaiwan andChina. The largest producer of acetone isINEOS Phenol, owning 17% of the world's capacity, with also significant capacity (7–8%) byMitsui,Sunoco andShell in 2010.[40] INEOS Phenol also owns the world's largest production site (420,000 tonnes/annum) inBeveren (Belgium).Spot price of acetone in summer 2011 was 1100–1250 USD/tonne in the United States.[42]
Acetone is produced directly or indirectly frompropene. Approximately 83% of acetone is produced via thecumene process;[24] as a result, acetone production is tied to phenol production. In the cumene process,benzene isalkylated with propylene to producecumene, which isoxidized by air to producephenol and acetone:
Other processes involve the direct oxidation of propylene (Wacker-Hoechst process), or thehydration of propylene to give2-propanol, which is oxidized (dehydrogenated) to acetone.[24]
Like most ketones, acetone exhibits theketo–enol tautomerism in which the nominalketo structure(CH3)2C=O of acetone itself is in equilibrium with theenol isomer(CH3)C(OH)=(CH2) (prop-1-en-2-ol). In acetone vapor at ambient temperature, only 2.4×10−7% of the molecules are in the enol form.[46]
In the presence of suitablecatalysts, two acetone molecules also combine to form the compounddiacetone alcohol(CH3)C=O(CH2)C(OH)(CH3)2, which ondehydration givesmesityl oxide(CH3)C=O(CH)=C(CH3)2. This product can further combine with another acetone molecule, with loss of another molecule of water, yieldingphorone and other compounds.[47]
Acetone is a weak Lewis base that forms adducts with soft acids likeI2 and hard acids likephenol. Acetone also forms complexes with divalent metals.[48][49]
At its melting point (−96 °C) is claimed to polymerize to give a white elastic solid, soluble in acetone, stable for several hours at room temperature. To do so, a vapor of acetone is co-condensed withmagnesium as a catalyst onto a very cold surface.[52][53][54]
Humans exhale several milligrams of acetone per day. It arises from decarboxylation ofacetoacetate.[55][56] Small amounts of acetone are produced in the body by thedecarboxylation ofketone bodies. Certain dietary patterns, including prolonged fasting and high-fat low-carbohydrate dieting, can produceketosis, in which acetone is formed in body tissue. Certain health conditions, such as alcoholism and diabetes, can produceketoacidosis, uncontrollable ketosis that leads to a sharp, and potentially fatal, increase in the acidity of the blood. Since it is a byproduct of fermentation, acetone is a byproduct of the distillery industry.[55]
Acetone is a good solvent for many plastics and some synthetic fibers. It is used for thinningpolyester resin, cleaning tools used with it, and dissolving two-partepoxies andsuperglue before they harden. It is used as one of the volatile components of somepaints andvarnishes. As a heavy-duty degreaser, it is useful in the preparation of metal prior to painting orsoldering, and to removerosin flux after soldering (to prevent adhesion of dirt and electrical leakage and perhaps corrosion or for cosmetic reasons), although it may attack some electronic components, such as polystyrene capacitors.[61]
Although itselfflammable, acetone is used extensively as a solvent for the safe transportation and storage ofacetylene, which cannot be safelypressurized as a pure compound. Vessels containing a porous material are first filled with acetone followed by acetylene, which dissolves into the acetone. One litre of acetone can dissolve around 250litres of acetylene at a pressure of 10 bars (1.0 MPa).[62][63]
Because acetone is cheap, volatile, and dissolves or decomposes with most laboratory chemicals, an acetone rinse is the standard technique to remove solid residues fromlaboratory glassware before a final wash.[66] Despite commondesiccatory use, acetone dries only via bulk displacement and dilution. It forms noazeotropes with water (seeazeotrope tables).[67] Acetone also removes certainstains frommicroscope slides.[68]
Acetone freezes well below −78 °C. An acetone/dry ice mixturecools many low-temperature reactions.[69]Make-up artists use acetone to remove skin adhesive from the netting of wigs and mustaches by immersing the item in an acetone bath, then removing the softened glue residue with a stiff brush.[70] Acetone is a main ingredient in many nail polish removers because it breaks down nail polish.[71] It is used for all types of nail polish removal, like gel nail polish, dip powder and acrylic nails.[72]
Proteins precipitate in acetone.[73] The chemical modifies peptides, both at α- or ε-amino groups, and in a poorly understood but rapid modification of certain glycine residues.[73]
Acetone has been shown to haveanticonvulsant effects in animal models ofepilepsy, in the absence of toxicity, when administered in millimolar concentrations.[77] It has been hypothesized that the high-fat low-carbohydrateketogenic diet used clinically to control drug-resistant epilepsy in children works by elevating acetone in the brain.[77] Because of their higher energy requirements, children have higher acetone production than most adults – and the younger the child, the higher the expected production. This indicates that children are not uniquely susceptible to acetone exposure. External exposures are small compared to the exposures associated with the ketogenic diet.[78]
Acetone's most hazardous property is its extreme flammability. In small amounts, acetone burns with adull blue flame; in larger amounts, fuel evaporation causes incomplete combustion and abright yellow flame. When hotter than acetone'sflash point of −20 °C (−4 °F), air mixtures of 2.5‑12.8% acetone (by volume) may explode or cause aflash fire. Vapors can flow along surfaces to distant ignition sources and flash back.
Static discharge may also ignite acetone vapors, though acetone has a very high ignition initiation energy and accidental ignition is rare.[79] Acetone'sauto-ignition temperature is the relatively high 465 °C (869 °F);[19] moreover, auto-ignition temperature depends upon experimental conditions, such as exposure time, and has been quoted as high as 535 °C.[80] Even pouring or spraying acetone over red-glowing coal will not ignite it, due to the high vapour concentration and the cooling effect of evaporation.[79]
Acetone occurs naturally as part of certain metabolic processes in the human body, and has been studied extensively and is believed to exhibit only slight toxicity in normal use. There is no strong evidence of chronic health effects if basic precautions are followed.[84] It is generally recognized to have low acute and chronic toxicity if ingested and/or inhaled.[85] Acetone is not currently regarded as acarcinogen, amutagen, or a concern for chronicneurotoxicity effects.[79]
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 agenerally recognized as safe (GRAS) substance when present in drinks, baked foods, desserts, and preserves at concentrations ranging from 5 to 8 mg/L.[85]
Acetone is however an irritant, causing mild skin and moderate-to-severe eye irritation. At high vapor concentrations, it may depress thecentral nervous system like many other solvents.[86] Acute toxicity for mice by ingestion (LD50) is 3 g/kg, and by inhalation (LC50) is 44 g/m3 over 4 hours.[87]
Although acetone occurs naturally in the environment in plants, trees, volcanic gases, forest fires, and as a product of the breakdown of body fat,[88] the majority of the acetone released into the environment is of industrial origin.[clarification needed] Acetone evaporates rapidly, even from water and soil. Once in the atmosphere, it has a 22-day half-life and is degraded by UV light viaphotolysis (primarily intomethane andethane.[89]) Consumption by microorganisms contributes to the dissipation of acetone in soil, animals, or waterways.[88]
In 1995, theUnited States Environmental Protection Agency (EPA) removed acetone from the list ofvolatile organic compounds. The companies requesting the removal argued that it would "contribute to the achievement of several important environmental goals and would support EPA's pollution prevention efforts", and that acetone could be used as a substitute for several compounds that are listed as hazardous air pollutants (HAP) under section 112 of theClean Air Act.[90] In making its decision EPA conducted an extensive review of the available toxicity data on acetone, which was continued through the 2000s. It found that the evaluable "data are inadequate for an assessment of the human carcinogenic potential of acetone".[9]
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