General Description
A colorless watery liquid with a sweet odor. Less dense than water. Insoluble in water. Irritating vapor.
Reactivity Profile
O-XYLENE(95-47-6) may react with oxidizing materials. .
Air & Water Reactions
Highly flammable. Insoluble in water.
Health Hazard
Vapors cause headache and dizziness. Liquid irritates eyes and skin. If taken into lungs, causes severe coughing, distress, and rapidly developing pulmonary edema. If ingested, causes nausea, vomiting, cramps, headache, and coma. Can be fatal. Kidney and liver damage can occur.
Fire Hazard
Behavior in Fire: Vapor is heavier than air and may travel considerable distance to a source of ignition and flash back.
Physical properties
Clear, colorless liquid with an aromatic odor. An odor threshold concentration of 380 ppbv was
reported by Nagata and Takeuchi (1990).
Definition
ChEBI: A xylene substituted by methyl groups at positions 1 and 3.
Flammability and Explosibility
Flammable
Chemical Reactivity
Reactivity with Water No reaction; Reactivity with Common Materials: No reaction; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.
Source
Detected in distilled water-soluble fractions of 87 octane gasoline (3.83 mg/L), 94 octane
gasoline (11.4 mg/L), Gasohol (8.49 mg/L), No. 2 fuel oil (1.73 mg/L), jet fuel A (0.87 mg/L),
diesel fuel (1.75 mg/L), military jet fuel JP-4 (1.99 mg/L) (Potter, 1996), new motor oil (16.2 to 17.5 μg/L), and used motor oil (294 to 308 μg/L) (Chen et al., 1994). The average volume percent
and estimated mole fraction in American Petroleum Institute PS-6 gasoline are 2.088 and 0.01959,
respectively (Poulsen et al., 1992). Schauer et al. (1999) reported o-xylene in a diesel-powered
medium-duty truck exhaust at an emission rate of 830 μg/km. Diesel fuel obtained from a service
station in Schlieren, Switzerland contained o-xylene at a concentration of 223 mg/L (Schluep et
al., 2001).
California Phase II reformulated gasoline contained o-xylene at a concentration of 19.7 g/kg.
Gas-phase tailpipe emission rates from gasoline-powered automobiles with and without catalytic
converters were 5.41 and 562 mg/km, respectively (Schauer et al., 2002).
Thomas and Delfino (1991) equilibrated contaminant-free groundwater collected from
Gainesville, FL with individual fractions of three individual petroleum products at 24–25 °C for
24 h. The aqueous phase was analyzed for organic compounds via U.S. EPA approved test method
602. Average m+p-xylene concentrations reported in water-soluble fractions of unleaded gasoline,
kerosene, and diesel fuel were 8.611, 0.658, and 0.228 mg/L, respectively. When the authors
analyzed the aqueous-phase via U.S. EPA approved test method 610, average m+p-xylene
concentrations in water-soluble fractions of unleaded gasoline, kerosene, and diesel fuel were
lower, i.e., 6.068, 0.360, and 0.222 mg/L, respectively.
Based on laboratory analysis of 7 coal tar samples, o-xylene concentrations ranged from 2 to
2,000 ppm (EPRI, 1990). A high-temperature coal tar contained o-xylene at an average
concentration of 0.04 wt % (McNeil, 1983).
Schauer et al. (2001) measured organic compound emission rates for volatile organic
compounds, gas-phase semi-volatile organic compounds, and particle-phase organic compounds
from the residential (fireplace) combustion of pine, oak, and eucalyptus. The gas-phase emission
rate of o-xylene was 18.1 mg/kg of pine burned. Emission rates of o-xylene were not measured
during the combustion of oak and eucalyptus.
Drinking water standard (final): For all xylenes, the MCLG and MCL are both 10 mg/L. In
addition, a DWEL of 70 mg/L was recommended (U.S. EPA, 2000).
Environmental Fate
Biological. Reported biodegradation products of the commercial product containing xylene
include α-hydroxy-p-toluic acid, p-methylbenzyl alcohol, benzyl alcohol, 4-methylcatechol, mand
p-toluic acids (Fishbein, 1985). o-Xylene was also cometabolized resulting in the formation of
o-toluic acid (Pitter and Chudoba, 1990). In anoxic groundwater near Bemidji, MI, o-xylene
anaerobically biodegraded to the intermediate o-toluic acid (Cozzarelli et al., 1990). In gasolinecontaminated
groundwater, methylbenzylsuccinic acid was identified as the first intermediate
during the anaerobic degradation of xylenes (Reusser and Field, 2002).
Photolytic. Cox et al. (1980) reported a rate constant of 1.33 x 10-11 cm3/molecule?sec for the
reaction of gaseous o-xylene with OH radicals based on a value of 8 x 10-12 cm3/molecule?sec for
the reaction of ethylene with OH radicals.
Surface Water. The evaporation half-life of o-xylene in surface water (1 m depth) at 25 °C is
estimated to be 5.18 h (Mackay and Leinonen, 1975).
Groundwater. Nielsen et al. (1996) studied the degradation of o-xylene in a shallow,
glaciofluvial, unconfined sandy aquifer in Jutland, Denmark. As part of the in situ microcosm study, a cylinder that was open at the bottom and screened at the top was installed through a cased
borehole approximately 5 m below grade. Five liters of water was aerated with atmospheric air to
ensure aerobic conditions were maintained. Groundwater was analyzed weekly for approximately
3 months to determine o-xylene concentrations with time. The experimentally determined firstorder
biodegradation rate constant and corresponding half-life following a 7-d lag phase were
0.1/d and 6.93 d, respectively.
Photolytic. When synthetic air containing gaseous nitrous acid and o-xylene was exposed to
artificial sunlight (λ = 300–450 nm) biacetyl, peroxyacetal nitrate, and methyl nitrate formed as
products (Cox et al., 1980). A n-hexane solution containing o-xylene and spread as a thin film (4
mm) on cold water (10 °C) was irradiated by a mercury medium pressure lamp. In 3 h, 13.6% of
the o-xylene photooxidized into o-methylbenzaldehyde, o-benzyl alcohol, o-benzoic acid, and omethylacetophenone
(Moza and Feicht, 1989). Irradiation of o-xylene at ≈ 2537 ? at 35 °C and 6
mmHg isomerizes to m-xylene (Calvert and Pitts, 1966). Glyoxal, methylglyoxal, and biacetyl
were produced from the photooxidation of o-xylene by OH radicals in air at 25 °C (Tuazon et al.,
1986a).
Chemical/Physical. Under atmospheric conditions, the gas-phase reaction of o-xylene with OH
radicals and nitrogen oxides resulted in the formation of o-tolualdehyde, o-methylbenzyl nitrate,
nitro-o-xylenes, 2,3-and 3,4-dimethylphenol (Atkinson, 1990). Kanno et al. (1982) studied the
aqueous reaction of o-xylene and other aromatic hydrocarbons (benzene, toluene, m- and p-xylene,
and naphthalene) with hypochlorous acid in the presence of ammonium ion. They reported that the
aromatic ring was not chlorinated as expected but was cleaved by chloramine forming cyanogen
chloride. The amount of cyanogen chloride formed increased at lower pHs (Kanno et al., 1982). In
the gas phase, o-xylene reacted with nitrate radicals in purified air forming the following products:
5-nitro-2-methyltoluene and 6-nitro-2-methyltoluene, o-methylbenzaldehyde, and an aryl nitrate
(Chiodini et al., 1993).
Purification Methods
o-Xylene (4.4Kg) is sulfonated by stirring for 4hours with 2.5L of conc H2SO4 at 95o. After cooling, and separating the unsulfonated material, the product is diluted with 3L of water and neutralised with 40% NaOH. On cooling, sodium o-xylene sulfonate separates and is recrystallised from half its weight of water. [A further crop of crystals is obtained by concentrating the mother liquor to one-third of its volume.] The salt is dissolved in the minimum amount of cold water, then mixed with the same amount of cold water, and with the same volume of conc H2SO4 and heated to 110o. o-Xylene is regenerated and steam distils. The distillate is saturated with NaCl, the organic layer is separated, dried and redistilled. [Beilstein 5 H 362, 5 I 179, 5 II 281, 5 III 807, 5 IV 917.]
