''m''-Xylene ( ''meta''-xylene) is an

aromatic hydrocarbon Aromatic compounds, also known as "mono- and polycyclic aromatic hydrocarbons", are organic compounds containing one or more aromatic rings. The parent member of aromatic compounds is benzene. The word "aromatic" originates from the past grouping ...

. It is one of the three

isomer In chemistry, isomers are molecules or polyatomic ions with identical molecular formulae – that is, same number of atoms of each element – but distinct arrangements of atoms in space. Isomerism is existence or possibility of isomers. Iso ...

s of dimethylbenzene known collectively as

xylene In organic chemistry, xylene or xylol (; IUPAC name: dimethylbenzene) are any of three organic compounds with the formula . They are derived from the substitution of two hydrogen atoms with methyl groups in a benzene ring; which hydrogens are sub ...

s. The ''m-'' stands for ''meta-'', indicating that the two methyl groups in ''m''-xylene occupy positions 1 and 3 on a benzene ring. It is in the positions of the two methyl groups, their

arene substitution pattern Arene substitution patterns are part of organic chemistry IUPAC nomenclature and pinpoint the position of substituents other than hydrogen in relation to each other on an aromatic hydrocarbon. ''Ortho'', ''meta'', and ''para'' substitution * I ...

, that it differs from the other isomers, ''o''-xylene and ''p''-xylene. All have the same chemical formula C₆H₄(CH₃)₂. All xylene isomers are colorless and highly flammable.

Production and use

Petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

contains about 1 weight percent xylenes. The ''meta'' isomer can be isolated from a mix of xylenes by the partial sulfonation (to which other isomers are less prone) followed by removal of unsulfonated oils and steam distillation of the sulfonated product. The major use of ''meta''-xylene is in the production of

isophthalic acid Isophthalic acid is an organic compound with the formula C6H4(CO2H)2. This colorless solid is an isomer of phthalic acid and terephthalic acid. The main industrial uses of purified isophthalic acid (PIA) are for the production of polyethylene te ...

, which is used as a

copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are some ...

izing

monomer In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification Mo ...

to alter the properties of

polyethylene terephthalate Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods ...

. The conversion ''m''-xylene to isophthalic acid entails

catalytic Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

. ''meta''-Xylene is also used as a raw material in the manufacture of 2,4- and 2,6-

xylidine Xylidine can refer to any of the six isomers of xylene amine, or any mixture of them. The chemical formula of xylidines is C8H11N or, more descriptively, (CH3)2C6H3NH2. The CAS number for the isomer mixture is . They are colorless solids or liqui ...

as well as a range of smaller-volume chemicals.Ashford's Dictionary of Industrial Chemicals, third edition, page 9692.

Ammoxidation In organic chemistry, ammoxidation is a process for the production of nitriles () using ammonia () and oxygen (). It is sometimes called the SOHIO process, acknowledging that ammoxidation was developed at Standard Oil of Ohio. The usual substrate ...

gives

isophthalonitrile Isophthalonitrile is an organic compound with the formula C6H4(CN)2. Two other isomers exist, phthalonitrile and terephthalonitrile. All three isomers are produced commercially by ammoxidation of the corresponding xylene isomers. Isophthalonitr ...

Toxicity and exposure

Xylenes are not acutely toxic, for example the (rat, oral) is 4300 mg/kg. Effects vary with animal and xylene isomer. Concerns with xylenes focus on narcotic effects.

References

{{Hydrocarbons Alkylbenzenes C2-Benzenes

Production and use

Toxicity and exposure

See also

References