is a non-protonic organic solvent.

]Its chemical formula is C4H8O2, with a relative molecular mass of approximately 88.11. It appears as a colorless transparent liquid with a slight fragrant ester-like odor.^[45-46

]It has a boiling point of 101.32°C, a freezing point of 11.80°C, a relative density of 1.0329, a flash point of 5~18°C, and a refractive index of 1.4175. Its dissolving capacity is similar to dimethylformamide and stronger than tetrahydrofuran. It is miscible with water and most organic solvents.^[43

]This cyclic ether can undergo ring-opening reactions and, under specific conditions, coupling reactions.