Toluene

March 18, 2019
I’m a solvent, but so much more.
What molecule am I?

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 vapor Chemical Safety Warning
GHS classification: aspiration hazard, category 1
H304—May be fatal if swallowed and enters airways Chemical Safety Warning
GHS classification: skin irritation, category 2
H315—Causes skin irritation Chemical Safety Warning
GHS classification: specific target organ toxicity, single exposure, central nervous system, category 3
H336—May cause drowsiness or dizziness Chemical Safety Warning
GHS classification: reproductive toxicity, category 2
H361—Suspected of damaging fertility or the unborn child Chemical Safety Warning
GHS classification: specific target organ toxicity, repeated exposure, category 2
H373—May cause damage to organs through prolonged or repeated exposure Chemical 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 formula C7H8
Molar mass 92.14 g/mol
Appearance Colorless liquid
Boiling point 111 ºC
Water solubility 526 mg/L

Toluene statistics

Global demand (2018)

≈27 million tonnes

Production
From oil refineries 75%
From ethylene steam crackers 20%
Styrene byproduct, coke oven light oil 5%
Usage
Interconversion to benzene and xylenes 50%
Blending into gasoline to raise octane number 25%
Solvent 18%
Toluene diisocyanate feedstock 5%
Benzoic acid feedstock 2%

Courtesy IHS Markit Ltd.

Chemical Abstract Service - a division of ACS

Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.

Molecule of the Week needs your suggestions!

If your favorite molecule is not in our archive, please send an email to motw@acs.org. The molecule can be notable for its current or historical importance or for any quirky reason. Thank you!

Stay Ahead of the Chemistry Curve

Learn how ACS can help you stay ahead in the world of chemistry.