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p-Xylene (para-xylene) is an aromatic hydrocarbon. It is one of the three isomers of dimethylbenzene known collectively as xylenes . The p- stands for para- , indicating that the two methyl groups in p -xylene occupy the diametrically opposite substituent positions 1 and 4.
The physical properties of the isomers of xylene differ slightly. The melting point ranges from −47.87 °C (−54.17 °F) (m-xylene) to 13.26 °C (55.87 °F) (p-xylene)—as usual, the para isomer's melting point is much higher because it packs more readily in the crystal structure. The boiling point for each isomer is around 140 °C (284 °F).
Diethylbenzenes arise as side-products of the alkylation of benzene with ethylene, which can be described as two steps. The first step is the industrial route to ethylbenzene, which is produced on a large scale as a precursor to styrene.
m-xylene (1,3-dimethylbenzene) p-xylene (1,4-dimethylbenzene) Other. Ethylbenzene (not a true xylene but present in mixtures called "mixed xylenes") Styrene;
Petroleum contains about one weight percent xylenes. Most o-xylene is produced by cracking petroleum, which affords a distribution of aromatic compounds, including xylene isomers.
For example, the three isomers of xylene CH 3 C 6 H 4 CH 3, commonly the ortho-, meta-, and para-forms, are 1,2-dimethylbenzene, 1,3-dimethylbenzene, and 1,4-dimethylbenzene. The cyclic structures can also be treated as functional groups themselves, in which case they take the prefix "cyclo alkyl -" (e.g. "cyclohexyl-") or for benzene, "phenyl-".
In the current systematic nomenclature, o-, m- and p- are often replaced by using locants (1,2-dimethylbenzene instead of o-xylene). o -, m - and p - (written out ortho -, meta - and para -) are written in lowercase letters and italic.
m-Xylene (meta-xylene) is an aromatic hydrocarbon.It is one of the three isomers of dimethylbenzene known collectively as xylenes.The m-stands for meta-, indicating that the two methyl groups in m-xylene occupy positions 1 and 3 on a benzene ring.