Furan (Oxole) is the simplest oxygen-containing five-element heterocyclic compound. It exists in the pine tar, colorless liquid, boiling point of 32 ℃, with a similar smell of chloroform, insoluble in water, soluble in organic solvents. Its vapor, which has been soaked in hydrochloric acid by the Pine film, is green, called the pine reaction, can be used to identify the presence of furan. It has anesthesia and weak stimulation, extremely flammable. Inhalation can cause headaches, dizziness, nausea, respiratory failure. Furan Ring has aromatic ring property, can be halogenated, nitrification, sulfonation and other nucleophilic substitution reaction, mainly used for organic synthesis or as a solvent.