Abstract: To provide a method and a composition for producing a geometric isomer (isomer 2) represented by a certain formula (1) by geometrically isomerizing a corresponding geometric isomer (isomer 1) represented by the certain formula (1), the method including, contacting the geometric isomer (isomer 1) represented by the certain formula (1) with a compound (A) which is at least one of a dichlorotrifluoropropane and hydrogen chloride in a gas phase.

Abstract: An object is to provide a hydrofluoroolefin-based or hydrochlorofluoroolefin-based azeotropic or azeotropic-like composition. The azeotropic or azeotropic-like composition contains trans-1-chloro-3,3,3-trifluoropropene and 1-chloro-1,3,3,3-tetrafluoropropene. In the azeotropic or azeotropic-like composition, 1-chloro-1,3,3,3-tetrafluoropropene exists in an effective amount to form an azeotropic or azeotropic-like mixture with trans-1-chloro-3,3,3-trifluoropropene.

Abstract: According to an embodiment, a method for producing a (hydro)halocarbon includes a step of purifying the (hydro)halocarbon by reduced-pressure distillation of an azeotropic or azeotropic-like composition containing the (hydro)halocarbon and a compound different from the (hydro)halocarbon. According to another embodiment, a method for producing a (hydro)halocarbon includes a step purifying the (hydro)halocarbon by reduced-pressure distillation of an azeotropic or azeotropic-like composition containing the (hydro)halocarbon and a compound different from the (hydro)halocarbon, wherein standard boiling points of both the (hydro)halocarbon and the compound are 80° C. or lower.