1,4-Dioxane

Colorless, flammable, somewhat oily, pleasant -smelling liquid

Liquid

1.03 g · cm -3

11.8 ° C

101 ° C.

38 hPa ( 20 ° C)

1.422 (20 ° C)

Risk

20 ml · m-3

5700 mg · kg -1 ( LD50, mouse, oral)

Template: Infobox chemical / molecular formula search available

1,4- dioxane is an alicyclic diether and as such an organic heterocyclic compound.

Production and representation

In the first step ethylene is converted by catalytic acid (concentrated sulfuric acid), ring-opening with water as a nucleophile in ethylene glycol (1,2- ethanediol ). The second and third steps, respectively describes the acid-catalyzed SN2 substitution, the second of which takes place intramolecularly. Protonation and deprotonation steps each were omitted for reasons of space.

Dioxane is also very easy as a by-product of acid-catalyzed reactions of all ethylene glycol or diethylene glycol ( eg esterification ).

Properties

1,4-dioxane is a colorless and low-viscosity liquid, boiling at atmospheric pressure at 101 ° C. The vapor pressure function is given by Antoine corresponding log10 (P) = A- ( B / ( T C )) ( P in bar, T in K) with A = 4.58135, B = 1570.093 and C = -31 297 in the temperature range 293-378 K. In the solid phase, there are two different crystal forms. At 0 ° C to Form II converts to Form I, which melts at 11 ° C. The cyclic diether is miscible with water. The apparently symmetrical molecule is such as cyclohexane or pyranose ago in the chair form and has a dipole moment of 0.45 D ( for comparison: tetrahydrofuran has a dipole moment of 1.63 D).

Dioxane is readily miscible with most organic solvents and water. At normal pressure dioxane / water at 82.1 mass percent of dioxane is observed azeotropic boiling point of 87.6 ° C in the binary system.

Binary phase diagram of the 1,4-dioxane / water.

Use

Because it is relatively inert, and because of its good miscibility with other solvents, is used as a solvent 1,4-dioxane.

Safety characteristics

Dioxane forms flammable vapor - air mixtures. The compound has a flash point of 11 ° C. The explosive range is between 1.9 vol% (70 g/m3) as the lower explosive limit ( LEL) and 22.5 % by volume (820 g/m3 ) and upper explosive limit (UEL ). A correlation of the explosion limits of the vapor pressure of function results in a lower explosion point of 8 ° C and an upper explosion point of 58 ° C. The marginal gap width was determined to be 0.7 mm. The result is thus a mapping in the explosion group IIB. The ignition temperature is 375 ° C. The fabric falls within the temperature class T2. The electrical conductivity is very low with 5:10 -13 S · m -1.