August 05, 2019
I’m a useful solvent, but I have a dark side.
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Image of 1,4-Dioxane 3D Image of 1,4-Dioxane

March of this year was “Solvent Month” for Molecule of the Week. Another commonly used solvent is 1,4-dioxane, usually referred to simply as dioxane.1 It is a cyclic diether that has an odor similar to that of its more volatile cousin, diethyl ether.

In 1928, IG Farbenindustrie (precursor to BASF) patented a manufacturing process for dioxane in which diethylene glycol is heated with a small amount of sulfuric acid. Today, it is still produced in much the same way. It is used industrially as a solvent for cellulose esters and ethers, adhesives, inks, and many other materials.

Dioxane, however, is coming under regulatory pressure because of health and environmental concerns:

  • A suspected carcinogen, dioxane has been found to contaminate drinking water in 27 US states.
  • Significant amounts of the solvent have been found in groundwater in New York State, prompting a bill in the legislature that would ban it in cleaning and personal care products.
  • The US Occupational Safety and Health Administration is considering regulating worker exposure to dioxane.

1. Structural isomers 1,2- and 1,3-dioxane have been prepared, but they are not commercial products.

1,4-Dioxane hazard information

GHS classification*: flammable liquids, category 2
H225—Highly flammable liquid and vapor Chemical Safety Warning
GHS classification: serious eye damage/eye irritation, category 2A
H319—Causes serious eye irritation Chemical Safety Warning
GHS classification: specific target organ toxicity, single exposure, respiratory tract irritation, category 3
H335—May cause respiratory irritation Chemical Safety Warning
GHS classification: carcenogenicity, category 2
H351—Suspected of causing cancer Chemical Safety Warning

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

1,4-Dioxane fast facts

CAS Reg. No. 123-91-1
Empirical formula C4H8O2
Molar mass 88.11 g/mol
Appearance Colorless liquid
Melting point 11.8 ºC
Boiling point 101.1 ºC
Water solubility Miscible

MOTW update:
January 18, 2021

Dioxane is a valuable solvent that has many industrial and laboratory uses. In 2019, it came under regulatory pressure because it is a possible carcinogen and has been found in drinking water and groundwater in several states. On December 31, 2020, the US Environmental Protection Agency released a hastily compiled risk assessment of dioxane that pleased neither environmentalists, state attorneys general, nor the chemical industry. Among the report’s other shortcomings, EPA ignored drinking-water exposure; environmentalists and regulators say that this is dioxane’s greatest threat to the general population.

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