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 colorless slightly oily flammable liquid.[5]

o-Xylene
Skeletal formula
Space-filling model
Names
Preferred IUPAC name
1,2-Xylene
Systematic IUPAC name
2-Methyltoluene
Other names
ortho-Xylene
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.002.203
KEGG
RTECS number
  • ZE2450000
UNII
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)[1]
Solubility in ethanol very soluble
Solubility in diethyl ether very soluble
Vapor pressure 7 mmHg (20°C)[1]
-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 [2]
Hazards
Safety data sheet See: data page
External MSDS
Harmful (Xn) Flammable (F)
R-phrases (outdated) R11 R20 R21 R38
S-phrases (outdated) S25
NFPA 704 (fire diamond)
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g. gasolineHealth code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
3
2
0
Flash point 32 °C (90 °F; 305 K)
463 °C (865 °F; 736 K)[3]
Explosive limits 0.9%-6.7%[1]
100 ppm[3] (TWA), 150 ppm[3] (STEL)
Lethal dose or concentration (LD, LC):
6125 ppm (rat, 12 hr)
6125 ppm (human, 12 hr)[4]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 100 ppm (435 mg/m3)[1]
REL (Recommended)
 TWA 100 ppm (435 mg/m3) ST 150 ppm (655 mg/m3)[1]
IDLH (Immediate danger)
 900 ppm[1]
Related compounds
m-xylene
p-xylene
toluene
Supplementary data page
Refractive index (n),
Dielectric constant (εr), etc.
Thermodynamic
data
 Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y verify (what is YN ?)
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.[5] Related to their easy oxidation, the methyl groups are susceptible to halogenation. When treated with bromine, these groups are brominated, leading ultimately to the tetrabromide:[6]

C6H4(CH3)2 + 4 Br2 → C6H4(CHBr2)2 + 4 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.[5]

References
  1. NIOSH Pocket Guide to Chemical Hazards. "#0668". National Institute for Occupational Safety and Health (NIOSH).
  2. 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.
  3. "o-Xylene". International Chemical Safety Cards. ICSC/NIOSH. July 1, 2014.
  4. "Xylene (o-, m-, p-isomers)". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  5. Fabri, Jörg; Graeser, Ulrich; Simo, Thomas A. (2000). "Xylenes". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a28_433.
  6. Bill, J. C.; Tarbell, D. S. (1954). "o-Phthalaldehyde". Organic Syntheses. 34: 82. doi:10.15227/orgsyn.034.0082.
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