March 18, 2019
I’m a solvent, but so much more.
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March is MOTW Solvent Month! This is the third of four articles about key solvents—Ed.

Toluene, or toluol as it was once called, is the simplest aromatic hydrocarbon except for benzene. It was first isolated in 1837 from pine oil by Polish chemist Filip N. Walter. Four years later, French chemist Henri Étienne Sainte-Claire Deville isolated it from “tolu balsam” (extracted from the Colombian tree Myroxylon balsamum). Within the next 10 years, chemists settled on toluene as the name for the then-new substance.

As shown in the statistics table, almost all of the global toluene demand is produced in oil refineries or is a byproduct of ethylene crackers. Similarly, most of it is used to make other aromatics or as a gasoline additive. Its use as a solvent is relatively minor; but it is a primary ingredient in paints, lacquers, and resins. 

Toluene has largely replaced the more-toxic benzene as a solvent. Benzene is an established carcinogen, but the carcinogenicity of toluene is as yet undetermined.

Toluene hazard information

GHS classification*: Flammable liquids, category 2
H225—Highly flammable liquid and vaporChemical Safety Warning
GHS classification: aspiration hazard, category 1
H304—May be fatal if swallowed and enters airwaysChemical Safety Warning
GHS classification: skin irritation, category 2
H315—Causes skin irritationChemical Safety Warning
GHS classification: specific target organ toxicity, single exposure, central nervous system, category 3
H336—May cause drowsiness or dizzinessChemical Safety Warning
GHS classification: reproductive toxicity, category 2
H361—Suspected of damaging fertility or the unborn childChemical Safety Warning
GHS classification: specific target organ toxicity, repeated exposure, category 2
H373—May cause damage to organs through prolonged or repeated exposureChemical Safety Warning
GHS classification: acute aquatic toxicity, category 2
H401—Toxic to aquatic life

*Globally Harmonized System of Classification and Labeling of Chemicals. Explanation of pictograms.

Toluene fast facts

CAS Reg. No.108-88-3
Empirical formulaC7H8
Molar mass92.14 g/mol
AppearanceColorless liquid
Boiling point111 ºC
Water solubility526 mg/L

Toluene statistics

Global demand (2018)

≈27 million tonnes

From oil refineries75%
From ethylene steam crackers20%
Styrene byproduct, coke oven light oil5%
Interconversion to benzene and xylenes50%
Blending into gasoline to raise octane number25%
Toluene diisocyanate feedstock5%
Benzoic acid feedstock2%

Courtesy IHS Markit Ltd.

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