Abstract: The present disclosure provides a method for producing a reaction gas containing 1,1,2-trifluoroethane (R-143) and/or (E,Z)-1,2-difluoroethylene (R-1132(E,Z)) using a starting material that is easier to obtain than those used in conventional methods. Specifically, the present disclosure provides a method for producing a reaction gas containing 1,1,2-trifluoroethane (R-143) and/or (E,Z)-1,2-difluoroethylene (R-1132(E,Z)), the method comprising subjecting a starting material gas containing difluoromethane (R-32) to a reaction that involves thermal decomposition at a pressure of 0.6 MPaG or more and 2.0 MPaG or less and a temperature of 600° C. or more and 1000° C. or less, thereby obtaining the reaction gas.

Abstract: A method for efficiently obtaining trans-1-halo-2-fluoroethylene (E-isomer) and/or cis-1-halo-2-fluoroethylene (Z-isomer) is provided. The method for producing trans-1-halo-2-fluoroethylene (E-isomer) and/or cis-1-halo-2-fluoroethylene (Z-isomer) includes supplying a composition containing trans-1-halo-2-fluoroethylene (E-isomer) and/or cis-1-halo-2-fluoroethylene (Z-isomer) to a reactor to perform isomerization between the trans-1-halo-2-fluoroethylene (E-isomer) and the cis-1-halo-2-fluoroethylene (Z-isomer) in a liquid phase by performing light irradiation in the presence of a photosensitizer.