1,4-Dioxane

Overview
1,4-Dioxane, often just called dioxane, is a clear, colorless heterocyclic organic compound which is a liquid at room temperature and pressure. It has the molecular formula C4H8O2 and a boiling point of 101°C. It is commonly used as an aprotic solvent. 1,4-Dioxane has a weak smell similar to that of diethyl ether. There are also two other less common isomeric compounds, 1,2-dioxane and 1,3-dioxane. 1,2-Dioxane is a peroxide which forms naturally in old bottles of tetrahydrofuran.

1,4-Dioxane is classified as an ether, with each of its two oxygen atoms forming an ether functional group. It is more polar than diethyl ether, which also has four carbons, but only one ether functional group. Diethyl ether is rather insoluble in water, but 1,4-dioxane is miscible with water and is hygroscopic. Its higher polarity and slightly higher molecular mass also gives it a substantially higher boiling point than diethyl ether. When used as a solvent for a grignard reaction, Dioxane favorably affects the formation of magnesium halide salts in the Schlenk equilibrium.

The name dioxane should not be confused with dioxin, which is a different compound but is also a diether (two ether functional groups).



Uses
1,4-Dioxane is primarily used in solvent applications for the manufacturing sector; however, it is also found in fumigants and automotive coolant. Additionally, the chemical is also used as a foaming agent and appears as an accidental byproduct of the ethoxylation process in cosmetics manufacturing. It may contaminate cosmetics and personal care products such as deodorants, shampoos, toothpastes and mouthwashes.

It is also commonly used as an internal standard for calibrating chemical shifts in NMR, as tetramethylsilane (the compound to which all chemical shifts are ultimately referenced) is not soluble in D2O.

Safety & environmental concerns
Dioxanes combine with atmospheric oxygen on standing to form explosive peroxides, similar to many other ethers. Distillation of dioxanes concentrates these peroxides increasing the danger. Appropriate precautions should be taken.

1,4-dioxane is a known eye and respiratory tract irritant. It is suspected of causing damage to the central nervous system, liver and kidneys. Accidental worker exposure to 1,4-dioxane has resulted in several deaths. Dioxane is classified by the IARC as a Group 2B carcinogen: possibly carcinogenic to humans due to the fact that it is a known carcinogen in animals.

Like many solvents, 1,4-dioxane forms contamination plumes in groundwater when released to the environment. Groundwater supplies have been adversely impacted in several areas.

1,4-dioxane is highly soluble in groundwater, does not readily bind to soils, and readily leaches to groundwater. It is also resistant to naturally occurring biodegradation processes. Due to these properties, a 1,4-dioxane plume is often much larger (and further downgradient) than the associated solvent plume.