xilene

Xilene is a common variant spelling of xylene, a group of aromatic hydrocarbons with the formula C8H10, formally described as dimethylbenzenes. Three structural isomers exist—ortho-xylene, meta-xylene and para-xylene—each differing in the relative positions of two methyl groups on the benzene ring. Physical properties vary slightly by isomer; typical boiling points are near 138–144 °C and densities around 0.86–0.88 g·cm−3. Xylene is typically encountered as a mixture of isomers.

Xylene is produced primarily from petroleum refining and coal tar processing, and by catalytic reforming or toluene disproportionation. Major uses include solvents for paints, coatings, adhesives and printing inks; cleaning agents in the electronics and metal industries; and as a feedstock in the manufacture of terephthalic acid and phthalic anhydride. Para-xylene is particularly important as a precursor for polyethylene terephthalate (PET) production.

Occupational and public health considerations focus on xylene’s volatility and neurotoxic effects. Acute inhalation can cause dizziness, headache, nausea and central nervous system depression; high or repeated exposures may affect the liver, kidneys and cognitive function. Xylene is flammable and requires appropriate storage, ventilation and personal protective equipment. Regulatory agencies set workplace exposure limits (for example, many jurisdictions use an 8-hour time-weighted average of about 100 ppm) and guidelines for safe handling.

In the environment xylene is volatile and contributes to photochemical smog but is readily biodegraded under aerobic conditions, showing low potential for long-term bioaccumulation.