Xylene: Difference between revisions

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The term xylene or xylol refers to a mixture of three benzene derivatives which is used as a solvent in the printing, rubber, and leather industries. Xylene is a colorless, sweet-smelling liquid that is very flammable. Like other solvents, xylene is also used as an inhalant drug for its intoxicating properties.

Chemical properties

Xylene is a generic term for a group of three benzene derivatives which encompasses ortho-, meta-, and para- isomers of dimethyl benzene. The o-, m- and p- designations specify to which carbon atoms (of the benzene ring) the two methyl groups are attached. Counting the carbon atoms from one of the ring carbons bonded to a methyl group, and counting towards the second ring carbon bonded to a methyl group, the o- isomer has the IUPAC name of 1,2-dimethylbenzene, the m- isomer has the IUPAC name of 1,3-dimethylbenzene, and the p- isomer has the IUPAC name of 1,4-dimethylbenzene. Solvent grade xylene usually contains a small percentage of ethylbenzene as a contaminent.

The chemical properties differ slightly from isomer to isomer. The melting point is between −47.87 °C (−54.17 °F) (m-xylene) and 13.26 °C (55.87 °F) (p-xylene). The boiling point for each isomer is around 140 °C (284.00 °F). The density is at around 0.87 kg/L (7.26 lb/U.S. gallon or 8.72 lb/imp gallon) and thus is less dense than water. Xylene in air can be smelled at 0.08 to 3.7 parts of xylene per million parts of air (ppm) and can begin to be tasted in water at 0.53 to 1.8 ppm.

Applications

Xylene is used as a solvent and in the printing, rubber, and leather industries. p-Xylene is used as a feedstock in the production of terephthalic acid, which is a monomer used in the production of polymers. It is also used as a cleaning agent for steel and for silicon wafers and chips, a pesticide [1], a thinner for paint, and in paints and varnishes. It may be substituted for toluene to thin lacquers where slower drying is desired. It is found in small amounts in airplane fuel and gasoline. In animal studies it is often swabbed on the ears of rabbits to facilitate blood flow and collection, although the area must subsequently be cleansed with alcohol to prevent inflammation. Xylene is also used as a fixation agent for animal tissues.

Xylene Isomers

General

Common name

Xylenes

o-Xylene

m-Xylene

p-Xylene

Systematic name

Dimethylbenzenes

1,2-Dimethylbenzene

1,3-Dimethylbenzene

1,4-Dimethylbenzene

Other names

Xylols

o-Xylol;
Orthoxylene

m-Xylol;
Metaxylene

p-Xylol;
Paraxylene

Molecular formula

C₈H₁₀ (C₆H₄C₂H₆)

SMILES

Cc1c(C)cccc1

Cc1cc(C)ccc1

Cc1ccc(C)cc1

Molar mass

106.16 g/mol

Appearance

clear, colorless liquid

CAS number

[1330-20-7]

[95-47-6]

[108-38-3]

[106-42-3]

Properties

Density and phase

0.864 g/mL, liquid

0.88 g/mL, liquid

0.86 g/mL, liquid

Solubility in water

practically insoluble

Soluble in non-polar solvents such as aromatic hydrocarbons

Melting point

-47.4°C (-53.3°F; 226 K)

−25°C (-13°F; 248 K)

−48°C (-54.4°F; 225 K)

13°C (55.4°F; 286 K)

Boiling point

138.5°C (281.3°F; 412 K)

144°C (291.2°F; 417 K)

139°C (282.2°F; 412 K)

138°C (280.4°F; 411 K)

Viscosity

.812 cP at 20 °C (68 °F)

.62 cP at 20 °C (68 °F)

.34 cP at 30 °C (86 °F)

Hazards

Harmful (Xn)

24 °C (75 °F)

17 °C (63 °F)

25 °C (77 °F)

R/S statement

Template:R10, Template:R20/21, Template:R38: Template:S2, Template:S25

RTECS number

ZE2450000

ZE2275000

ZE2625000

Supplementary data page

Structure & properties

n, ε_r, etc.

Thermodynamic data

Phase behaviour
Solid, liquid, gas

Spectral data

UV, IR, NMR, MS

Related compounds

Related aromatic
hydrocarbons

toluene, mesitylene, benzene, ethylbenzene

Related compounds

xylenols - types of phenols

Except where noted otherwise, data are given for
materials in their standard state (at 25°C, 100 kPa)
Infobox disclaimer and references

Related compounds

Xylenes are a starting material for the production of other chemicals. For instance chlorination of both methyl groups gives three isomeric xylene dichlorides or 1,2-bis(chloromethyl)benzenes. With oxidizing agents, such as potassium permanganate (KMnO₄), the methyl group can be oxidized to a carboxylic acid. By oxidizing both methyl groups, o-xylene forms phthalic acid and p-xylene forms terephthalic acid.

In articles of commerce, the term xylol refers to the solvent mixture of three xylene isomers, sometimes containing ethylbenzene. In the chemical trade, this mixture is referred to as xylenes (plural). This substance must not be confused with the toxic and corrosive xyleneol compounds, which are dimethyl phenol isomers.

Health effects

Xylene exhibits neurological effects. High levels from exposure for acute (14 days or less) or chronic periods (more than 1 year) can cause headaches, lack of muscle coordination, dizziness, confusion, and changes in one's sense of balance^{[citation needed]} . Exposure of people to high levels of xylene for short periods can also cause irritation of the skin, eyes, nose, and throat, difficulty in breathing and other problems with the lungs, delayed reaction time, memory difficulties, stomach discomfort, and possibly adverse effects on the liver and kidneys. It can cause unconsciousness and even death at very high levels (see inhalants). Xylene or products containing Xylene should not be used indoors or around food.

Studies of unborn animals indicate that high concentrations of xylene may cause increased numbers of deaths, and delayed growth and development.^{[citation needed]} In many instances, these same concentrations also cause damage to the mothers. It is not yet known whether xylene harms the unborn fetus if the mother is exposed to low levels of xylene during pregnancy.

Besides occupational exposure, the principal pathway of human contact is via soil contamination from leaking underground storage tanks containing petroleum products. Humans who come into contact with the soil or groundwater may become affected. Use of contaminated groundwater as a water supply could lead to adverse health effects.

External links

International Chemical Safety Card 0084 (o-Xylene)
International Chemical Safety Card 0085 (m-Xylene)
International Chemical Safety Card 0086 (p-Xylene)
NIOSH Pocket Guide to Chemical Hazards (o-Xylene)
NIOSH Pocket Guide to Chemical Hazards (m-Xylene)
NIOSH Pocket Guide to Chemical Hazards (p-Xylene)
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 Studies of unborn animals indicate that high concentrations of xylene may cause increased numbers of deaths, and delayed growth and development.{{Fact|date=December 2007}} In many instances, these same concentrations also cause damage to the mothers. It is not yet known whether xylene harms the unborn fetus if the mother is exposed to low levels of xylene during pregnancy.
-Besides [[occupational hygiene|occupational exposure]], the principal pathway of human contact is via [[soil contamination]] from leaking [[underground storage tank]]s containing petroleum products.  Humans who come into contact with the soil or groundwater may become affected. Use of contaminated groundwater as a water supply could lead to adverse health effects. Nosipho Moloto
+Besides [[occupational hygiene|occupational exposure]], the principal pathway of human contact is via [[soil contamination]] from leaking [[underground storage tank]]s containing petroleum products.  Humans who come into contact with the soil or groundwater may become affected. Use of contaminated groundwater as a water supply could lead to adverse health effects.
 ==See also==