Description
Trichlorobenzenes (TCBs) are synthetic chemicals that
occur in three different isomeric forms. The three chlorinated
cyclic aromatic isomers are 1,2,3-trichlorobenzene (1,2,3-TCB),
1,2,4-trichlorobenzene (1,2,4-TCB), and 1,3,5-trichlorobenzene
(1,3,5-TCB). 1,2,4-TCB is one of the 188 chemicals designated
as a hazardous air pollutant under the Clean Air Act.
Chemical Properties
1,2,3-Trichlorobenzene and 1,3,5-trichlorobenzene are colorless solids, while 1,2,4-trichlorobenzene is a colorless liquid. Although the three isomers of trichlorobenzenes have the same molecular weight and formula, they each may have different chemical and toxicological properties. One of the isomers (1,2,4-trichlorobenzene) is produced in large quantities and is used as a solvent to dissolve such special materials as oils, waxes, resins, greases, and rubber. It is also frequently used to produce dyes and textiles. The other two isomers, 1,2,3-trichlorobenzene and 1,3,5-trichlorobenzene, are produced in lower quantities and have fewer uses.
Uses
Trichlorobenzenes are primarily used as solvents in chemical
manufacturing industries. 1,2,4-Trichlorobenzene is economically
the most important isomer. 1,2,4-Trichlorobenzene is
used as a solvent in chemical reactions to dissolve oils, waxes,
and resins. Furthermore, it is also used as a dye carrier. 1,2,3-
Trichlorobenzene is used as an intermediate for pesticides
production, pigments, and dyes. 1,3,5-Trichlorobenzene is not
marketed commercially and has very limited use as a chemical
intermediate. Besides, trichlorobenzenes can also be used as
degreasing agents, as septic tanks and drain cleaners, and as an
ingredient in wood preservatives and abrasive formulations.
Other minor uses include metal work, anticorrosive paint, and
corrosion inhibitor in sprays. In the past, mixed isomers of
trichlorobenzenes were used to control termites; however, their
use has been discontinued.
Uses
Detoxification by catalytic hydrotreatment of 1,2,3-Trichlorobenzene is used for the disposal of hazardous organic waste liquids. As constituent of trichlorobenzene mixt used for termite control. As transformer fluid, dye carrier & solvent. Solvent for high melting products, Coolant in electrical installations and glass tempering. In polyester dyeing, lubricants, Heat transfer medium. As chemical intermediate for 2,3-dichlorophenol.
Definition
ChEBI: 1,2,3-trichlorobenzene is a trichlorobenzene carrying chloro substituents at positions 1, 2 and 3.
General Description
A white solid with a sharp chlorobenzene odor. Insoluble in water and denser than water. Hence sinks in water. Melting point 63-64°C (145-147°F).
Air & Water Reactions
Insoluble in water.
Reactivity Profile
1,2,3-Trichlorobenzene can react with oxidizing agents. . May emit toxic hydrogen chloride and phosgene gases in fire.
Health Hazard
Inhalation may cause irritation of respiratory tract. Irritating to the eyes. May redden skin on contact. Ingestion may cause liver damage.
Environmental Fate
Biological. Under aerobic conditions, soil microbes are capable of degrading 1,2,3-
trichlorobenzene to 1,2- and 1,3-dichlorobenzene and carbon dioxide (Kobayashi and Rittman,
1982). A mixed culture of soil bacteria or a Pseudomonas sp. transformed 1,2,3-trichlorobenzene
to 2,3,4-, 3,4,5-, and 2,3,6-trichlorophenol (Ballschiter and Scholz, 1980).
In an enrichment culture derived from a contaminated site in Bayou d’Inde, LA, 1,2,3-
trichlorobenzene underwent reductive dechlorination to 1,2- and 1,3-dichlorobenzene at relative
molar yields of 1 and 99%, respectively. The maximum dechlorination rate, based on the
recommended Michaelis-Menten model, was 60 nM/d (Pavlostathis and Prytula, 2000).
Photolytic. The sunlight irradiation of 1,2,3-trichlorobenzene (20 g) in a 100-mL borosilicate
glass-stoppered Erlenmeyer flask for 56 d yielded 32 ppm pentachlorobiphenyl (Uyeta et al.,
1976).
Chemical/Physical. At 70.0 °C and pH values of 3.07, 7.13, and 9.80, the hydrolysis half-lives
were calculated to be 19.2, 15.0, and 34.4 d, respectively (Ellington et al., 1986).
Emits toxic chloride fumes when heated to decomposition.
Purification Methods
Crystallise it from EtOH. [Beilstein 5 IV 664.]
Toxicity evaluation
The liver is themain target of trichlorobenzenes irrespective of
the route of exposure. The mechanisms of liver toxicity
induced by these chemicals have not been illustrated. It might
involve intermediate arene oxides formed during initial
transformation to trichlorophenols. In addition, exposure
to 1,2,4-TCB induced porphyria in rats by inducing δ-aminolevulinic
acid (ALA) synthetase, a rate-limiting enzyme
in the biosynthesis of heme, and also heme oxygenase, a ratelimiting
enzyme in the degradation of heme synthetase, and
therefore increasing heme production.
