o-Xylene

o-Xylene (ortho-xylene) is an aromatic hydrocarbon with the formula C6H4(CH3)2, with two methyl substituents bonded to adjacent carbon atoms of a benzene ring (the ortho configuration). It is a constitutional isomer of m-xylene and p-xylene, the mixture being called xylene or xylenes. o-Xylene is a colourless slightly oily flammable liquid.[7]

o-Xylene
Skeletal formula
Skeletal formula
Space-filling model
Space-filling model
Names
Preferred IUPAC name
1,2-Xylene[1]
Systematic IUPAC name
1,2-Dimethylbenzene[1]
Other names
o-Xylene,[1] o-Xylol
Identifiers
3D model (JSmol)
1815558
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.002.203
EC Number
  • 202-422-2
67796
KEGG
RTECS number
  • ZE2450000
UNII
UN number 1307
  • InChI=1S/C8H10/c1-7-5-3-4-6-8(7)2/h3-6H,1-2H3 checkY
    Key: CTQNGGLPUBDAKN-UHFFFAOYSA-N checkY
  • InChI=1/C8H10/c1-7-5-3-4-6-8(7)2/h3-6H,1-2H3
    Key: CTQNGGLPUBDAKN-UHFFFAOYAE
  • CC1=C(C)C=CC=C1
Properties
C8H10
Molar mass 106.168 g·mol−1
Appearance Colorless liquid
Density 0.88 g/ml
Melting point −24 °C (−11 °F; 249 K)
Boiling point 144.4 °C (291.9 °F; 417.5 K)
0.02% (20°C)[2]
Solubility in ethanol very soluble
Solubility in diethyl ether very soluble
Vapor pressure 7 mmHg (20°C)[2]
-77.78·10−6 cm3/mol
1.50545
Viscosity 1.1049 cP at 0 °C
0.8102 cP at 20 °C
Structure
0.64 D[3]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Mildly toxic
GHS labelling:
GHS02: FlammableGHS07: Exclamation markGHS08: Health hazard
Danger
H225, H226, H304, H305, 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)
NFPA 704 four-colored diamond
2
3
0
Flash point 32 °C (90 °F; 305 K)
463 °C (865 °F; 736 K)[4]
Explosive limits 0.9%-6.7%[2]
100 ppm[4] (TWA), 150 ppm[4] (STEL)
Lethal dose or concentration (LD, LC):
4300 mg/kg (rats, orally)[5]
6125 ppm (rat, 12 hr)
6125 ppm (human, 12 hr)[6]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 100 ppm (435 mg/m3)[2]
REL (Recommended)
 TWA 100 ppm (435 mg/m3) ST 150 ppm (655 mg/m3)[2]
IDLH (Immediate danger)
 900 ppm[2]
Safety data sheet (SDS) External MSDS
Related compounds
m-xylene
p-xylene
toluene
Supplementary data page
O-Xylene (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)
Infobox references

Production and use

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. m-Xylene is isomerized to o-xylene. Net production was approximately 500,000 tons in the year 2000.

o-Xylene is largely used in the production of phthalic anhydride, which is a precursor to many materials, drugs, and other chemicals.[7] Related to their easy oxidation, the methyl groups are susceptible to halogenation. When treated with elemental bromine, these groups are brominated, yielding xylylene dibromide:[8]

C6H4(CH3)2 + 2 Br2 → C6H4(CH2Br)2 + 2 HBr

Toxicity and exposure

Xylenes are not acutely toxic, for example the LD50 (rat, oral) is 4300 mg/kg. Effects vary with animal and xylene isomer. Concerns with xylenes focus on narcotic effects.[7]

References
  1. Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. 121, 139, 653. doi:10.1039/9781849733069. ISBN 978-0-85404-182-4.
  2. NIOSH Pocket Guide to Chemical Hazards. "#0668". National Institute for Occupational Safety and Health (NIOSH).
  3. Rudolph, H.D.; Walzer, K.; Krutzik, Irmhild (1973). "Microwave spectrum, barrier for methyl rotation, methyl conformation, and dipole moment of ortho-xylene". Journal of Molecular Spectroscopy. 47 (2): 314. Bibcode:1973JMoSp..47..314R. doi:10.1016/0022-2852(73)90016-7.
  4. "o-Xylene". International Chemical Safety Cards. ICSC/NIOSH. July 1, 2014.
  5. O-xylene toxicity
  6. "Xylene (o-, m-, p-isomers)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  7. Fabri, Jörg; Graeser, Ulrich; Simo, Thomas A. (2000). "Xylenes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a28_433.
  8. Emily F. M. Stephenson (1954). "o-Xylylene Dibromide". Organic Syntheses. 34: 100. doi:10.15227/orgsyn.034.0100.
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