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2-butanone (or methyl ethyl ketone)

CAS number 78-93-3

                          

Identifiers

CAS number [78-93-3]
RTECS number EL6475000
SMILES CCC(=O)C

Properties
Molecular weight: 72.1057
Molecular formula C4H8O
Molar mass 72.11 g/mol
Appearance Colorless liquid
Density 0.8050 g/cm³
Melting point -86 °C, 187 K, -123 °F
Boiling point 79.6 °C, 353 K, 175 °F
Solubility in water 27.5%
Viscosity 0.43 cP at 20 °C

Structure

Dipole moment 2.76 D
Hazards
MSDS External
MSDS EU classification Flammable (F) Irritant (Xi)
R-phrases R11, R36, R66, R67
S-phrases (S2), S9, S16
Flash point −9 °C
Autoignition temperature 505 °C
LD50 6.86 ml/kg (oral, rat)

2-Butanone, also known as methyl ethyl ketone (MEK), is a colorless liquid with a sweet, but sharp odor. 2-Butanone is manufactured in large amounts for use in paints, glues, and other finishes because it rapidly evaporates and will dissolve many substances. It will quickly evaporate into the air. 2-Butanone is often found dissolved in water or as a gas in the air. 2-Butanone is also a natural product made by some trees and is found in some fruits and vegetables.

The exhausts of cars and trucks release 2-butanone into the air. 2-Butanone is usually found in the air, water, and soil of landfills and hazardous waste sites.

In water, 2-butanone can be changed to a more simple chemical form by natural biological processes and will be broken down in about 2 weeks. It will not be deposited in the sediment of rivers or lakes, and it is not expected to concentrate in fish. In air, 2-butanone will break down under the influene of sunlight, although it does not react with sunlight directly.

One-half of any given amount of 2-butanone in the air will break down in 1 day or less. It is not known if 2-butanone changes to a more simple form by natural biological processes in the soil, but it is expected to do so because similar substances are broken down by these processes.

2-Butanone will not stick to soil, and if it is spilled onto soil, it will travel through the soil into underground water sources. Some of the 2-butanone found in soil or water will also evaporate to the air.

Exposure

2-Butanone can enter the environment in a number of different ways. It can enter the air or water from the waste of manufacturing plants. 2-Butanone is present in many different types of paints and glues used both in the home and in industry.

As these products dry, 2-butanone will enter the air. 2-Butanone is also in air because it is released in the exhaust of cars and trucks. Some trees in the forest release 2-butanone to the air.

We do not know the background levels of 2-butanone in air, water, or soil. We know that 2-butanone is found naturally in some foods. We know it is found at hazardous waste sites, and it is also found occasionally in drinking water and often in the air of cities. You may also be exposed to 2-butanone by smoking cigarettes.

You may be exposed to higher levels of 2-butanone if you use glues or coatings containing it in a small enclosed area that does not have good air flow.

People who use it at work have a good chance of being exposed to 2-butanone. 2-Butanone is used in such industries as shoe factories, printing plants, plastics factories, and sporting goods manufacturers.

People who live near a toxic waste site where 2-butanone is kept may breathe it if it evaporates into the air, or drink it if it gets into the water supply, especially when the water supply come from wells.

Metabolism

2-Butanone can enter your body if you breathe air that contains it, through your skin if it touches you, or through your mouth if you eat food or drink water that has 2-butanone in it. Studies have shown that, if there is 2-butanone in the air you breathe, at least half of what you breathe in will enter your body.

The other half will leave in the air you breathe out. We do not know how much 2-butanone will stay in your body if you drink it or if it touches your skin. The amount of 2-butanone that actually enters your body depends on how much is in the air you breathe, how much is in your food or water, or how much gets on your skin.

The amount of 2-butanone that enters your body also depends on how long you breathe it or how long it is on your skin before you wash it off. Your body gets rid of 2-butanone in urine and in the air you breathe out. 2-butanone is not a chemical that stays in your body for very long; it will be gone by the next day.

Health Effects

Some people who breathed air that contained 2-butanone first noticed its sweet, sharp odor at a concentration of 5-8 parts of 2-butanone per million parts of air (5-8 ppm). The main health effects that have been seen in humans who breathed higher concentrations of 2-butanone are mild irritation of the nose, throat, eyes, and skin.

Serious health effects in animals have been seen only at very high concentrations of 2-butanone. These high concentrations are not expected in the usual use of 2-butanone or in the vicinity of hazardous waste sites. Studies in animals have shown that 2-butanone does not cause serious damage to the nervous system or the liver, but mice that breathed low levels for a short time had temporary behavioral effects. 2-Butanone alone does not have serious effects on the liver or nervous system, but it can cause other chemicals to become more harmful to these systems.

Guinea pigs, rats, and mice that breathed high levels of 2-butanone for a short time became unconscious and died. Pregnant rats and mice that breathed air containing high levels of 2-butanone had underdeveloped fetuses.

The rats that swallowed very high concentrations of 2-butanone in water also developed signs of nervous system effects such as inactivity, drooping eye lids, and uncoordinated muscle movement.

Some rats and mice that swallowed water containing high concentrations of 2-butanone died. Rats that received water containing a lower concentration of 2-butanone had mild kidney damage. Skin irritation developed in rabbits and guinea pigs that had small amounts of 2-butanone dropped on their skin. Rabbits that had small amounts of 2-butanone dropped in their eyes had serious eye irritation.

We do not know whether 2-butanone causes birth defects or affects reproduction in humans. Reproductive effects were not seen in animals exposed to 2-butanone. We have no information about whether 2-butanone causes cancer in humans or animals.

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