1,4-Dioxane

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1,4-Dioxane

Chemical name	1,4-Dioxane
Other names	[1,4]Dioxane p-Dioxane
Chemical formula	C₄H₈O₂
Molecular mass	88.11 g/mol
Melting point	11.8°C
Boiling point	101.1°C
Density	1.033 g/cm³
CAS number	[123-91-1]
EINECS number	204-661-8
SMILES	C1OCCOC1
Thermodynamic data
Standard enthalpy of formation Δ_fH°_liquid	-354 kJ/mol
Standard enthalpy of combustion Δ_cH°_liquid	-2363 kJ/mol
Standard molar entropy S°_liquid	196.6 J.K^–1.mol^–1
Safety data
EU classification	Flammable (F) Carc. Cat. 3 Irritant (Xn)
R-phrases	R11, R19, R36/37, R40, R66
S-phrases	S2, S9, S16, S36/37, S46
Disclaimer and references

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).

Isomers of Dioxane
Small blue numbers show numbering of atoms in rings.

[edit] Caution

All of the dioxanes are flammable liquids, similar to many other organic solvents.

Upon standing over time, dioxanes combine with oxygen from the air to form explosive peroxides, similar to many other ethers. Distillation of dioxanes concentrates these peroxides increasing the danger. Appropriate precautions should be taken.