xylene

xylene

xylene (zīˈlēn) or dimethylbenzene (dīˌmĕthəlbĕnˈzēn), C₆H₄(CH₃)₂, colorless, oily, liquid aromatic hydrocarbon, used extensively as a solvent, obtained from coal tar, wood tar, and sometimes from petroleum. It is a mixture of three isomers that differ structurally from one another in the location of the two methyl groups that have replaced hydrogen atoms in the benzene molecule. Ortho-xylene is 1,2-dimethylbenzene; it melts at −25℃ and boils at 144℃. Meta-xylene is 1,3-dimethylbenzene; it melts at −48℃ and boils at 139℃. Para-xylene is 1,4-dimethylbenzene; it melts at 13℃ and boils at 138℃. The separation of these three isomers from one another by fractional distillation is difficult because their boiling points are so close together. The ortho and para isomers are converted to meta-xylene by treatment with aluminum trichloride and hydrochloric acid at about 80℃. The xylenes are often used in the synthesis of other compounds, e.g., the xylidenes that are amino derivatives used in the synthesis of azo dyes and other compounds.

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xylene

[′zī‚lēn]

(organic chemistry)

C₆H₄(CH₃)₂ Any one of the family of isomeric, colorless aromatic hydrocarbon liquids, produced by the destructive distillation of coal or by the catalytic reforming of petroleum naphthenic fractions; used for high-octane and aviation gasolines, solvents, chemical intermediates, and the manufacture of polyester resins. Also known as dimethylbenzene; xylol.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

xylene

an aromatic hydrocarbon existing in three isomeric forms, all three being colourless flammable volatile liquids used as solvents and in the manufacture of synthetic resins, dyes, and insecticides; dimethylbenzene. Formula: C₆H₄(CH₃)₂

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005