1,2,4-Trimethylbenzene

Description

1,2,4-Trimethylbenzene (mesitylene) is an aromatic hydrocarbon compound commonly present in commercial solvents encompassing their boiling range. Mesitylene are the most common isomer used in commercial applications. Aromatic hydrocarbons in hydrocarbon solvents are predominantly alkylated one ring structures as well as two aromatic ring structures which may also be alkylated.

Chemical Properties

colourless liquid. Insoluble in water, soluble in ethanol, ether and benzene.

Physical properties

Colorless liquid with a slight aromatic odor. A detection odor threshold concentration of 12 mg/m³ (2.4 ppm_v) was experimentally determined by Dravnieks (1974).

Uses

1,2,4-Trimethylbenzene is the unlabelled version of 1,2,4-Trimethyl 13C6-benzene (T796173), a labelled aromatic standard.

Uses

Sterilizing catgut by heating one hour at 160°; solvent in manufacture of dyes, perfumes and resins. Solvent for liquid scintillation counting solutions.

Definition

ChEBI: 1,2,4-trimethylbenzene is a trimethylbenzene carrying methyl groups at positions 1, 2 and 4. It has a role as a neurotoxin.

Synthesis Reference(s)

Journal of the American Chemical Society, 73, p. 766, 1951 DOI: 10.1021/ja01146a079
Chemical and Pharmaceutical Bulletin, 34, p. 540, 1986 DOI: 10.1248/cpb.34.540

General Description

A liquid. Flash point near 130°F. Less dense than water and insoluble in water. Vapors irritate eyes, throat, and nose. Used in dyes and pharmaceuticals.

Air & Water Reactions

Insoluble in water.

Reactivity Profile

1,2,4-Trimethylbenzene is incompatible with the following: Oxidizers, nitric acid .

Hazard

Moderate fire risk. Central nervous system depressant, irritant to mucous membranes. Asthma and hematologic effects.

Health Hazard

Harmful if inhaled or swallowed. Vapor or mist is irritating to the eyes, mucous membrane and upper respiratory tract. Prolonged contact can cause dermatitis, nausea, headache, dizziness, and narcotic effect.

Safety Profile

Moderately toxic by intraperitoneal route. Mildly toxic by inhalation. Can cause central nervous system depression, anemia, bronchitis. Flammable liquid when exposed to heat, sparks, or flame. To fight fire, use foam, alcohol foam, mist. Emitted from modern building materials (CENEAR 69,22,91). When heated to decomposition it emits acrid smoke and irritating fumes.

Toxicology

Acute toxicity studies (oral, dermal and inhalation routes of exposure) have been conducted in rats. Oral LD50 values of greater than 5000 mg/kg have been reported. For solvent products containing predominantly mixed C9 aromatic hydrocarbons, oral LD50 values have been reported as greater than 6880 mg/kg (males) and greater than 3440 mg/kg (females). LC50 values of 18,000 mg/m3 was reported for 1,2,4-TMB. For C9 aromatic solvents, the LC50 was greater than 10,200 mg/m3 (Shell Research Laboratory, 1976, unpublished study). One dermal acute study showed an LD50 value of greater than 3440 mg/kg for a C9 aromatic solvent (Shellsol A, a highly aromatic solvent boiling in the white spirit range, consisting of primarily C9 isomers particularly TMBs)

Environmental Fate

Biological. In anoxic groundwater near Bemidji, MI, 1,2,4-trimethylbenzene anaerobically biodegraded to the intermediate 3,4-dimethylbenzoic acid and the tentatively identified compounds 2,4- and/or 2,5-dimethylbenzoic acid (Cozzarelli et al., 1990).
Photolytic. Glyoxal, methylglyoxal, and biacetyl were produced from the photooxidation of 1,2,4-trimethylbenzene by OH radicals in air at 25 °C (Tuazon et al., 1986a). A rate constant of 2.0 x 10^-8 L/moleculesec was reported for the reaction of 1,2,4-trimethylbenzene with OH radicals in the gas phase (Darnall et al., 1976). Similarly, the rate constants for the reaction of 1,2,4- trimethylbenzene and OH radicals at room temperature were 3.35 x 10^-11 (Hansen et al., 1975) and 3.84 x 10^-11 cm³/moleculesec (Atkinson, 1985). At 25 °C, a rate constant of 3.15 x 10^-11 cm³/moleculesec was reported for the same reaction (Ohta and Ohyama, 1985). Products identified from the OH radical-initiated reaction of 1,2,4-trimethylbenzene in the presence of nitrogen dioxide were 3-hexene-2,5-dione and 2,3-butanedione (Bethel et al., 2000).
Chemical/Physical. 1,2,4-Trimethylbenzene will not hydrolyze in water (Kollig, 1993).

Purification Methods

Reflux pseudocumene over sodium and distil it under reduced pressure. [Beilstein 6 H 1088, 6 I 542, 6 II 1072, 6 III 6278, 6 IV 7339.]

Toxics Screening Level

The initial threshold screening level (ITSL) for 1,2,4-trimethylbenzene is 185 μg/m3 based on an annual averaging time.