Xylene

C₈H₁₀

Xylene is an aromatic hydrocarbon which is widely used in industry and medical technology as a solvent. It is a colourless, and sweet-smelling liquid or gas which occurs naturally in petroleum, coal and wood tar, and is named so since it is found in crude wood spirit. It has a chemical formula of C₆H₄(CH₃)₂ and is called dimethyl benzene since it contains a six-carbon ring to which two methyl groups are attached. It exists in three different isomeric forms named ortho-, meta- and para-xylene. Xylene is an essential petrochemical that is produced by the process of catalytic reforming and by coal carbonisation in the coke fuel manufacturing. It also occurs in the crude oil in concentrations of around 0.5 to 1%, depending on the source. Small quantities of C₈H₁₀ occur in gasoline and aircraft fuels as well. In this article, we will know about what is xylene, the chemical structure of xylene, xylene formula, preparation of xylene, properties of xylene, and much more.

What is Xylene?

Xylene is an organic chemical compound which is also called dimethyl benzene or xylol. It is one of the three isomers of the compound dimethylbenzene. It consists of a central benzene ring which is attached with two methyl groups as substituents. In the year 1850, xylene was first isolated by a French chemist named Auguste Cahors. Xylene is a colourless, clear, and flammable liquid which is produced by the catalytic reforming as well as by the coal carbonisation. It also occurs naturally in crude oil, gasoline, aircraft fuels. The mixture of xylene is a bit greasy and has a sweet smell, which is generally encountered as a solvent.

The commercially obtained xylene is a colourless, flammable, and nonviscous, toxic liquid. It does not dissolve in water, however, is miscible with several organic liquids. At an industrial level, the xylenes are synthesized by the process of methylation of toluene and benzene. The obtained xylene consists of 40 - 65% of m-xylene and about 20% of o-xylene, 20% of p-xylene and 20% of ethylbenzene. 

Xylene Structure

Let us see the xylene molecular structure now.

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Xylene exists in three different isomeric forms. These isomers can be distinguished by the designations ortho- (o-), meta- (m-) and para- (p-), that specify to which carbon atoms (of the benzene ring) the two methyl groups are attached. By counting the carbon atoms around the ring starting from one of the ring carbons bonded to a methyl group, and counting towards the second methyl group, the o-isomer has the IUPAC name of 1,2-dimethylbenzene, the m-isomer is 1,3-dimethylbenzene and the p-isomer is 1,4-dimethylbenzene. Of the three isomers, the p-isomer is the most industrially sought after since it can be oxidized to terephthalic acid.

Let us now take a look at the physical properties of xylene and the chemical properties of xylene.

Properties of Xylene

Xylene formula

C₆H₄(CH₃)₂

Xylene molecular weight

106.16 g/mol

Xylene density

0.864 g/mL

Xylene boiling point

138.5 °C

Xylene melting point

−47.4 °C


Xylene Uses

Let us now look at what is xylene used for.

  1. Xylene is used in the form of a raw material in the manufacturing of fibres, films, and dyes.

  2. It is used in the laboratories for cooling the reaction vessels.

  3. It is used in the form of a clearing agent.

  4. It is used to make the thick varnishes and paints thinner.

  5. It was used as a tear gas agent during World War I.

Xylene Side Effects

Xylene affects the brain to a greater extent. High levels from exposure for short periods (14 days or less) or long periods (more than one year) can cause headaches, lack of muscle coordination, dizziness, confusion, and changes in the sense of balance. Exposure of people to high levels of xylene for short periods can also lead to the irritation of the skin, eyes, nose, and throat. It also causes difficulty in breathing, problems with the lungs, delayed reaction time, memory difficulties, stomach discomfort, and possible changes in the liver and the kidneys. It can also cause unconsciousness and even death at very high levels.

Studies of unborn animals indicate that the higher concentrations of xylene may cause increased numbers of deaths, and delayed growth and development. In many instances, these same concentrations also lead to 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.

FAQ (Frequently Asked Questions)

1. What is Xylene?

Xylene is a colourless liquid which has a sweet odour. It is highly flammable and practically insoluble. It is primarily a synthetic chemical, but it can occur naturally in coal, coal tar, and during forest fires.

There are three different forms of xylene that are meta-xylene, ortho-xylene and para-xylene. These different forms are called isomers. Collectively, these three isomers of xylene are called total xylenes.

2. What is the Use of Xylene?

The para isomer of xylene is known to be amongst the principal precursors to dimethyl terephthalate and terephthalic acid. Both these compounds are monomers which are used for the production of polyethylene terephthalate which is often abbreviated as PET. This compound is also widely used as a solvent. In the chemical laboratories, reaction vessels are generally cooled by using the dry ice and xylene baths. This compound is also essential for the production of xylene bromides and xylene chlorides.