What molecule am I?
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 |  |
| GHS classification: serious eye damage/eye irritation, category 2A | |
| H319—Causes serious eye irritation |  |
| GHS classification: specific target organ toxicity, single exposure, respiratory tract irritation, category 3 | |
| H335—May cause respiratory irritation | |
| GHS classification: carcenogenicity, category 2 | |
| H351—Suspected of causing cancer |  |
*Globally Harmonized System of Classification and Labeling of Chemicals. Explanation of pictograms.
MOTW update: November 18, 2019
Former Molecules of the Week 1,4-dioxane, hexabromocyclododecane, 1-bromopropane, N-methyl-2-pyrrolidone, and dichloromethane, among several other chemicals, are at the center of a controversy about how the EPA’s scientific advisory committees are evaluating risks of air pollution. The problems are the lack of expertise in some of the committees and a shortage of adquate data to evaluate the chemicals. Industrial and environmental stakeholders are critical of the latest risk assessments.
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.
Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.
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