Ortho-xylene (o-xylene) is one of the three isomers of xylene, alongside meta-xylene (m-xylene) and para-xylene (p-xylene). It is an aromatic hydrocarbon with the chemical formula C₆H₆(CH₃)₂, consisting of a benzene ring with two methyl groups (CH₃) attached at the 1,2-positions (hence the “ortho” designation, referring to their relative position). Ortho-xylene is produced primarily from petroleum and coal tar and is commonly used in the production of various chemicals, solvents, and as an intermediate in industrial processes. It is a colorless, flammable liquid with a sweet odor, and it is soluble in many organic solvents.
Properties of Ortho-Xylene:
- Molecular Formula: C₆H₆(CH₃)₂
- IUPAC Name: 1,2-Dimethylbenzene
- Boiling Point: 144°C (291.2°F)
- Melting Point: -25.2°C (-13.36°F)
- Density: 0.88 g/cm³ at 20°C
- Flash Point: 25°C (77°F) – flammable
- Solubility: Slightly soluble in water, but very soluble in organic solvents such as ether, acetone, benzene, and toluene.
Key Uses of Ortho-Xylene:
Production of Phthalic Anhydride:
The primary use of ortho-xylene is in the production of phthalic anhydride, which is a precursor to many plasticizers, dyes, and resins. Phthalic anhydride is particularly important in the production of alkyd resins used in paints and coatings.
Solvent:
Ortho-xylene is used as a solvent in the production of paints, lacquers, adhesives, and coatings due to its ability to dissolve a wide range of materials, especially plastics and resins. It is also used in rubber and leather industries for solvent-based formulations.
Plasticizers:
Ortho-xylene is used in the manufacture of plasticizers like dioctyl phthalate (DOP), which are used in PVC (polyvinyl chloride) plastics to increase flexibility and durability.
Production of Terephthalic Acid:
In some cases, ortho-xylene can be converted to terephthalic acid (TPA), a key component in the production of polyester fibers and plastic bottles.
Pesticides and Insecticides:
Ortho-xylene derivatives are sometimes used as intermediates in the synthesis of pesticides and insecticides.
Pharmaceuticals:
Like other aromatic compounds, ortho-xylene may be used as a solvent in certain pharmaceutical formulations.