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o-Xylene
Skeletal formula	Space-filling model
Names
	Preferred IUPAC name 1,2-Xylene
	Systematic IUPAC name 1,2-Dimethylbenzene
	Other names o-Xylene, o-Xylol
Identifiers
CAS Number	95-47-6 ;
3D model (JSmol)	Interactive image;
Beilstein Reference	1815558
ChEBI	CHEBI:28063 ;
ChEMBL	ChEMBL45005 ;
ChemSpider	6967 ;
DrugBank	DB03029 ;
ECHA InfoCard	100.002.203
EC Number	202-422-2;
Gmelin Reference	67796
KEGG	C07212 ;
PubChem CID	7237;
RTECS number	ZE2450000;
UNII	Z2474E14QP ;
UN number	1307
CompTox Dashboard (EPA)	DTXSID3021807 ;
	InChI InChI=1S/C8H10/c1-7-5-3-4-6-8(7)2/h3-6H,1-2H3 Key: CTQNGGLPUBDAKN-UHFFFAOYSA-N ; InChI=1/C8H10/c1-7-5-3-4-6-8(7)2/h3-6H,1-2H3 Key: CTQNGGLPUBDAKN-UHFFFAOYAE;
	SMILES CC1=C(C)C=CC=C1;
Properties
Chemical formula	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)
Solubility in water	0.02% (20°C)
Solubility in ethanol	very soluble
Solubility in diethyl ether	very soluble
Vapor pressure	7 mmHg (20°C)
Magnetic susceptibility (χ)	-77.78·10−6 cm3/mol
Refractive index (nD)	1.50545
Viscosity	1.1049 cP at 0 °C; 0.8102 cP at 20 °C
Structure
Dipole moment	0.64 D
Hazards
	Occupational safety and health (OHS/OSH):
Main hazards	Mildly toxic
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H225, H226, H304, H305, H312, H315, H319, H332, H335, H412
Precautionary statements	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)	2 3 0
Flash point	32 °C (90 °F; 305 K)
Autoignition; temperature	463 °C (865 °F; 736 K)
Explosive limits	0.9%-6.7%
Threshold limit value (TLV)	100 ppm (TWA), 150 ppm (STEL)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	4300 mg/kg (rats, orally)
LCLo (lowest published)	6125 ppm (rat, 12 hr); 6125 ppm (human, 12 hr)
	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	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). verify (what is ?) Infobox references

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]

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

^ ^a ^b ^c 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.
^ ^a ^b ^c ^d ^e ^f NIOSH Pocket Guide to Chemical Hazards. "#0668". National Institute for Occupational Safety and Health (NIOSH).
^ 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.
^ ^a ^b ^c "o-Xylene". International Chemical Safety Cards. ICSC/NIOSH. July 1, 2014.
^ O-xylene toxicity
^ "Xylene (o-, m-, p-isomers)". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
^ ^a ^b ^c Fabri, Jörg; Graeser, Ulrich; Simo, Thomas A. (2000). "Xylenes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a28_433. ISBN 978-3527306732.
^ Emily F. M. Stephenson (1954). "o-Xylylene Dibromide". Organic Syntheses. 34: 100. doi:10.15227/orgsyn.034.0100.