Composition, production method for composition, and production method for unsaturated compound

A method of producing a composition, comprising steps of:

• producing a mixture comprising the compound (A) and the compound (B);
• and
• purifying the mixture by a distillation process at a reflux ratio of 2.0 to 4.0, a pressure of 1.0 to 10.0 kPa and a distillation temperature of 90 to 140° C.,
• wherein the purifying step comprises:
• a vacuum breaking step of supplying a gas having a dew point of −30° C. or less in a distillation apparatus after distillation by the distillation process and returning the pressure in the distillation apparatus to atmospheric pressure, wherein the gas comprises nitrogen gas oxygen gas at an oxygen concentration of 1 vol % or more and less than the critical oxygen concentration of compound (A);
• and
• a filling step of storing the purified product in the distillation apparatus after distillation in a container and filling a gas phase portion in the container with air having a dew point of −30° C. or lower.