p-Xylene
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. It is in the positions of the two methyl groups, their arene substitution pattern, that it differs from the other isomers, o-xylene and m-xylene. All have the same chemical formula C6H4(CH3)2. All xylene isomers are colorless and highly flammable. The odor threshold of p-xylene is 0.62 parts per million (ppm).
Space-filling model | |
| Names | |
|---|---|
| Preferred IUPAC name
1,4-Xylene | |
| Systematic IUPAC name
1,4-dimethylbenzene | |
| Other names
p-Xylene, p-dimethylbenzene; p-xylol; 1,4-xylene; p-methyltoluene; paraxylene; chromar; scintillar; 4-methyltoluene; NSC 72419; or 1,4-dimethylbenzene. | |
| Identifiers | |
3D model (JSmol) |
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| 1901563 | |
| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| ECHA InfoCard | 100.003.088 |
| EC Number |
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| 2697 | |
| KEGG | |
PubChem CID |
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| RTECS number |
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| UNII | |
CompTox Dashboard (EPA) |
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| Properties | |
| C8H10 | |
| Molar mass | 106.168 g·mol−1 |
| Appearance | Colorless liquid |
| Odor | Aromatic |
| Density | 0.861 g/mL |
| Melting point | 13.2 °C (55.8 °F; 286.3 K) |
| Boiling point | 138.35 °C (281.03 °F; 411.50 K) |
| Insoluble | |
| Solubility in ethanol | Very soluble |
| Solubility in diethyl ether | Very soluble |
| Vapor pressure | 9 mmHg (20°C) |
| -76.78·10−6 cm3/mol | |
Refractive index (nD) |
1.49582 |
| Viscosity | 0.7385 cP at 0 °C 0.6475 cP at 20 °C |
| 0.00 D | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards |
Harmful or if swallowed. Vapor maybe toxic. Flammable liquid and vapor. |
| GHS labelling: | |
| Danger | |
| H226, H302, H304, H312, H315, H319, H332, H335, H412 | |
| P210, P233, P240, P241, P242, P243, P261, P264, P271, P273, P280, P301+P310, P302+P352, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P312, P321, P322, P331, P332+P313, P337+P313, P362, P363, P370+P378, P403+P233, P403+P235, P405, P501 | |
| NFPA 704 (fire diamond) | |
| Flash point | 27 °C (81 °F; 300 K) |
| 528 °C (982 °F; 801 K) | |
| Explosive limits | 1.1%-7.0% |
Threshold limit value (TLV) |
100 ppm (TWA), 150 ppm (STEL) |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) |
4300 mg/kg |
LC50 (median concentration) |
4550 ppm (rat, 4 hr) |
LCLo (lowest published) |
3401 ppm (mouse) |
| NIOSH (US health exposure limits): | |
PEL (Permissible) |
TWA 100 ppm (435 mg/m3) |
REL (Recommended) |
TWA 100 ppm (435 mg/m3) ST 150 ppm (655 mg/m3) |
IDLH (Immediate danger) |
900 ppm |
| Safety data sheet (SDS) | External MSDS |
| Related compounds | |
Related aromatic hydrocarbons |
benzene toluene o-xylene m-xylene |
| Supplementary data page | |
| P-Xylene (data page) | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references | |
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