 | |
 Space-filling model | |
| Names | |
|---|---|
| Preferred IUPAC name 1,4-Xylene[4] | |
| Systematic IUPAC name 1,4-dimethylbenzene | |
| Other names | |
| Identifiers | |
| |
3D model (JSmol) | |
| 1901563 | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
|
| ECHA InfoCard | 100.003.088 |
| EC Number |
|
| 2697 | |
| KEGG |
|
| RTECS number |
|
| UNII | |
| |
| |
| Properties | |
| C8H10 | |
| Molar mass | 106.168 g·mol−1 |
| Appearance | Colorless liquid |
| Odor | Aromatic[5] |
| 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 inethanol | Very soluble |
| Solubility indiethyl ether | Very soluble |
| Vapor pressure | 9 mmHg (20 °C)[5] |
| −76.78·10−6 cm3/mol | |
Refractive index (nD) | 1.49582 |
| Viscosity | 0.7385 cP at 0 °C 0.6475 cP at 20 °C |
| 0.00D[6] | |
| Hazards | |
| Occupational safety and health (OHS/OSH): | |
Main hazards | Harmful or if swallowed. Vapor maybe toxic.[7] 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)[8] |
| 528 °C (982 °F; 801 K)[8] | |
| Explosive limits | 1.1%-7.0%[5] |
Threshold limit value (TLV) | 100 ppm[8] (TWA), 150 ppm[8] (STEL) |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 4300 mg/kg[9] |
LC50 (median concentration) | 4550 ppm (rat, 4 hr)[10] |
LCLo (lowest published) | 3401 ppm (mouse)[10] |
| NIOSH (US health exposure limits): | |
PEL (Permissible) | TWA 100 ppm (435 mg/m3)[5] |
REL (Recommended) | TWA 100 ppm (435 mg/m3) ST 150 ppm (655 mg/m3)[5] |
IDLH (Immediate danger) | 900 ppm[5] |
| Safety data sheet (SDS) | External MSDS |
| Related compounds | |
Relatedaromatic hydrocarbons | benzene toluene o-xylene m-xylene |
| Supplementary data page | |
| P-Xylene (data page) | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
p-Xylene (para-xylene) is anaromatic hydrocarbon. It is one of the threeisomers ofdimethylbenzene known collectively asxylenes. Thep- stands forpara-, indicating that the two methyl groups inp-xylene occupy the diametrically opposite substituent positions 1 and 4. It is in the positions of the two methyl groups, theirarene substitution pattern, that it differs from the other isomers,o-xylene andm-xylene. All have the same chemical formula C6H4(CH3)2. All xylene isomers are colorless and highly flammable. The odor threshold ofp-xylene is 0.62parts per million (ppm).[11]
The production ofp-xylene is industrially significant, with annual demand estimated at 37 million tons in 2014, and still on the increase.[12][13]p-Xylene is produced bycatalytic reforming of petroleumnaphtha as part of theBTX aromatics (benzene, toluene and the xylene isomers) extracted from the catalytic reformate. Thep-xylene is then separated out in a series of distillation, adsorption or crystallization and reaction processes from them-xylene,o-xylene, andethylbenzene. Its melting point is the highest among this series of isomers, but simple crystallization does not allow easy purification due to the formation ofeutectic mixtures.
Such separation procedures are major cost factors in the production ofp-xylene, and the search for alternative methods continues. For example, a reverse-osmosis technique has been proposed to improve various aspects of the processes.[14]
p-Xylene is an important chemicalfeedstock. Among other industrial applications, it is a raw material in the large scale synthesis of variouspolymers. In particular it is a component in the production ofterephthalic acid forpolyesters such aspolyethylene terephthalate (generally known as PET). It also may be polymerised directly to produceparylene.
Xylenes are not acutely toxic, for example theLD50 (rat, oral) is 4300 mg/kg. Effects vary with animal and xylene isomer.
Concerns with xylenes focus on narcotic effects. Overexposure ofp-xylene in humans can cause headache, fatigue, dizziness, listlessness, confusion, irritability, gastrointestinal disturbances including nausea and loss of appetite, flushing of the face, and a feeling of increased body heat.p-Xylene vapor exposure over the recommended exposure limit of 100 parts per million (ppm) can cause irritation to eye, nose, and throat and possible chest tightening and an abnormal gait.[15]
p-Xylene occurs naturally in petroleum and coal tar. It is emitted by most combustion sources, including automobile exhaust andtobacco smoke.[16]
Inhalingp-xylene can cause dizziness, headache, drowsiness, and nausea. If exposure through inhalation occurs, first aid includes fresh air, rest and possible medical attention. Through the use of ventilation or breathing protection, exposure top-xylene through inhalation can be prevented.[17]
Exposure ofp-xylene through the skin can cause dry skin and redness. If skin exposure occurs, first aid includes rinsing and then washing the affected area with soap and water as well as removing any contaminated clothing and thoroughly cleaning and drying before reuse. Exposure can be prevented through the use of protective gloves.[17]
Exposure ofp-xylene to eyes can cause redness and pain. If eyes are exposed, first aid includes rinsing of the eyes with water for several minutes, removal of contact lenses if applicable, and medical attention. Eye exposure can be prevented through the use of safety glasses or safety goggles.[17]
Ingestion ofp-xylene can result in a burning sensation, abdominal pain, dizziness, drowsiness, headache, and nausea. Ifp-xylene is ingested one's mouth should be rinsed and vomiting should not be induced. Further medical attention should be sought. Ingestion can be prevented by not eating, drinking, or smoking when working withp-xylene.[17]
p-Xylene can cause issues with the central nervous system and if swallowed could cause chemical pneumonitis when breathed into the lungs.[17]
Liquidp-xylene exposure to the skin over long periods of time can remove the fat from the skin. The substance may also have effects on thecentral nervous system. Exposure can enhance hearing loss caused by noise exposure. Animal tests suggest that this substance could cause damage to human development and reproductive systems.[17]
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