1,4 Methods for the synthesis of dioxanes

1,4-Dioxane (1,4-Dioxane), molecular formula C4H8O2, molecular weight, colorless liquid. Slightly scented. Density, refractive index.

Melting point 11. Boiling point. Miscible with water and many organic solvents.

It is prepared by joint distillation and dehydration of ethylene glycol and concentrated phosphoric acid. It is a solvent for cellulose acetate, resin, vegetable oil, mineral oil, oil dissolt dyes, etc., and is also used to make spray paints, varnishes, plasticizers, wetting agents, etc.

The substance commonly known as dioxane is 1,4-dioxane in chemical structure. See Fig

Appearance and properties: colorless, ether-smelling liquid.

Melting point ( ) relative density (water = 1):

Boiling point ( ) relative vapor density (air = 1):

Saturation vapor pressure (kpa):

Heat of combustion (kj mol):

Critical temperature ( ) 312

Critical Pressure (MPa):

Flash point ( ) 12

**Upper Limit %(v v):

Ignition temperature ( ) 180

**Lower Limit %(v v):

Solubility: miscible with water, miscible in most organic solvents Basic thermochemical properties Numerical unit Temperature (k) References Status Heat capacity cp j (mol·k) 50 g j (mol·k) 100 g j (mol·k) 150 g j (mol·k) 200 g j (mol·k) g 146 j (mol·k) 291 l j (mol·k) 296 l j (mol·k) 298 l j (mol·k) 298 l l 149 j (mol·k) 298 l j (mol·k) 298 l j (mol·k) g j (mol·k) l 149 j (mol·k) l j (mol·k) l j (mol·k) l j (mol·k) l j (mol·k) l j (mol·k) l j (mol·k) l j (mol·k) l j (mol·k) 300 g j (mol·k) 400 g j (mol·k) 500 g j (mol·k) 600 g j (mol·k) 700 g j (mol·k) 800 g j (mol·k) 900 g j (mol·k) 1000 g j (mol·k) 1100 g j (mol·k) 1200 g j (mol·k) 1300 g j (mol·k) 1400 g j (mol·k) 1500 g standard enthalpy -318 kj mol g kj mol g kj mol l kj mol l Standard entropy j (mol·k) g j (mol·k) l

It is obtained by the reaction of paraformaldehyde with ethylene glycol. Paraformaldehyde and ethylene glycol were put into the reaction kettle at a ratio of 1:mol, and a strong acidic ion exchange resin was used as a catalyst for atmospheric pressure reaction at 90-110.

The 70-74 azeotrope is distilled from the top of the distillation column, and after the sodium chloride salting out and anhydrous calcium chloride dehydration, then distillation and purification, the 71-74 fraction is cut, and the water is removed to 200ppm with a molecular sieve to obtain the finished product. Another operation is to make paraformaldehyde react with ethylene glycol in the presence of concentrated sulfuric acid, and then salt out sodium chloride; The solid alkali is dried and the product is obtained by rectification. Raw material consumption quota:

paraformaldehyde (93-95%) 750kg t; Ethylene glycol 200kg t.