Azeotrope is a mixture of two or more liquids, at a certain Has a constant boiling point and composition over the pressure range. Azeotropes form when the intermolecular forces between molecules in a mixture are stronger than those in a pure liquid.

The formation of N-methylmorpholine-water azeotrope is due to The hydrogen bonds between N-methylmorpholine and water molecules are stronger than those between pure N-methylmorpholine or pure water molecules. Stronger hydrogen bonds in the azeotrope prevent molecules from escaping into the gas phase until the temperature rises to 114.5 °C.