Ethylene glycol is the simplest aliphatic dihydric alcohol with chemical properties of alcohols such as being capable of generating ether, ester, or being oxidized into acid or aldehyde as well as being condensed to form ether or being substituted by halogen. Its reaction with acyl chloride or acid anhydride generally forms di-esters. Under heating in the presence of catalyst (manganese dioxide, aluminum oxide, zinc oxide or sulfuric acid), it can be subject to intermolecular or intramolecular dehydration to form the cyclic ethylene acetals, which can react with nitric acid to generate glycol dinitrate (an explosive). Ethylene glycol is the raw material for production of polyester resins, alkyd resins and polyester fiber. It can also be used as the refrigerant agent for automobile and aircraft engines refrigerant. In 1980, the glycol amount used as refrigerant agent is equal to the amount consumption for producing polyester. In addition, it can also be used for synthesizing polymers such as polyester fibers. Ethylene glycol dinitrate, when used in combination with nitroglycerine can reduce the freezing point of explosives. Ethylene glycol can also be used as the raw material of pharmaceuticals and plastics and high-boiling solvents. Industry applied ethylene as a raw material with first converting it to ethylene oxide and then hydrolyzing to produce ethylene glycol.