According to a method for producing a perfluoroalkadiene compound represented by general formula (1): CF.sub.2═CF—(CF.sub.2).sub.n-4—CF═CF.sub.2 (1), wherein n is an integer of 4 or more, the method comprising a reaction step of adding a nitrogen-containing compound to a solution of a compound represented by general formula (2): X.sup.1CF.sub.2—CFX.sup.2—(CF.sub.2).sub.n-4—CF.sub.2—CF.sub.2X.sup.1 (2), wherein n is the same as above, X.sup.1 is the same or different and is a halogen atom other than fluorine, and X.sup.2 is a halogen atom, the perfluoroalkadiene compound can be obtained at a high yield.

A plasma etching method according to an embodiment is a method for etching a silicon-containing film by using plasma of a fluorocarbon gas. The fluorocarbon gas includes at least one selected from a first fluorocarbon which has a main chain of six or more carbons bonded in a linear manner, the main chain having a structure of single bond and double bond alternately joined, a second fluorocarbon which has a main chain of six or more carbons bonded in a linear manner, the main chain having a structure of single bond and triple bond alternately joined, and a third fluorocarbon which has a main chain of five or more carbons bonded in a linear manner, the main chain having a structure which includes double bond and triple bond.

A plasma etching method according to an embodiment is a method for etching a silicon-containing film by using plasma of a fluorocarbon gas. The fluorocarbon gas includes at least one selected from a first fluorocarbon which has a main chain of six or more carbons bonded in a linear manner, the main chain having a structure of single bond and double bond alternately joined, a second fluorocarbon which has a main chain of six or more carbons bonded in a linear manner, the main chain having a structure of single bond and triple bond alternately joined, and a third fluorocarbon which has a main chain of five or more carbons bonded in a linear manner, the main chain having a structure which includes double bond and triple bond.

According to a method for producing a perfluoroalkadiene compound represented by general formula (1): CF.sub.2═CF—(CF.sub.2).sub.n-4—CF═CF.sub.2 (1), wherein n is an integer of 4 or more, the method comprising a reaction step of adding a nitrogen-containing compound to a solution of a compound represented by general formula (2): X.sup.1CF.sub.2—CFX.sup.2—(CF.sub.2).sub.n-4—CF.sub.2—CF.sub.2X.sup.1 (2), wherein n is the same as above, X.sup.1 is the same or different and is a halogen atom other than fluorine, and X.sup.2 is a halogen atom, the perfluoroalkadiene compound can be obtained at a high yield.

According to a method for producing a perfluoroalkadiene compound represented by general formula (1): CF.sub.2═CF—(CF.sub.2).sub.n-4—CF═CF.sub.2 (1), wherein n is an integer of 4 or more, the method comprising a reaction step of adding a nitrogen-containing compound to a solution of a compound represented by general formula (2): X.sup.1CF.sub.2—CFX.sup.2—(CF.sub.2).sub.n-4—CF.sub.2—CF.sub.2X.sup.1 (2), wherein n is the same as above, X.sup.1 is the same or different and is a halogen atom other than fluorine, and X.sup.2 is a halogen atom, the perfluoroalkadiene compound can be obtained at a high yield.

By subjecting a starting material composition containing hexafluorobutadiene and at least one additional compound selected from the group consisting of octafluoro-1-butene, octafluoro-2-butene, heptafluoro-1-butene, and heptafluoro-2-butene to extractive distillation in the presence of an extraction solvent to reduce the concentration of the additional compound, hexafluorobutadiene with higher purity can be obtained.

By subjecting a starting material composition containing hexafluorobutadiene and at least one additional compound selected from the group consisting of octafluoro-1-butene, octafluoro-2-butene, heptafluoro-1-butene, and heptafluoro-2-butene to extractive distillation in the presence of an extraction solvent to reduce the concentration of the additional compound, hexafluorobutadiene with higher purity can be obtained.

By subjecting a starting material composition containing hexafluorobutadiene and at least one additional compound selected from the group consisting of octafluoro-1-butene, octafluoro-2-butene, heptafluoro-1-butene, and heptafluoro-2-butene to extractive distillation in the presence of an extraction solvent to reduce the concentration of the additional compound, hexafluorobutadiene with higher purity can be obtained.

An object of the present invention is to provide a simple, low-cost, and industrial method of producing a compound having a polyene skeleton containing hydrogen and fluorine and/or chlorine. A method of producing a halogenated diene represented by formula (1): A.sup.1A.sup.2C═CA.sup.3-CA.sup.4=CA.sup.5A.sup.6 [A.sup.1, A.sup.2, A.sup.5, and A.sup.6 are each independently hydrogen, fluorine, chlorine, a (perfluoro)alkyl group having 1 to 3 carbon atoms, or a (perfluoro)alkenyl group; A.sup.3 and A.sup.4 are each independently hydrogen, fluorine, or chlorine; at least one of A.sup.1 to A.sup.6 is hydrogen; at least one of A.sup.1 to A.sup.6 is fluorine or chlorine] comprises a step of subjecting the same or different halogenated olefin(s) represented by formula (2): A.sup.7A.sup.8C═CA.sup.9X [A.sup.7 and A.sup.8 are each independently hydrogen, fluorine, chlorine, a (perfluoro)alkyl group having 1 to 3 carbon atoms, or a (perfluoro)alkenyl group; A.sup.9 is each independently hydrogen, fluorine, or chlorine; X is bromine or iodine] to a coupling reaction in the presence of a zero-valent metal and a metal salt.

An object of the present invention is to provide a simple, low-cost, and industrial method of producing a compound having a polyene skeleton containing hydrogen and fluorine and/or chlorine. A method of producing a halogenated diene represented by formula (1): A.sup.1A.sup.2C═CA.sup.3-CA.sup.4=CA.sup.5A.sup.6 [A.sup.1, A.sup.2, A.sup.5, and A.sup.6 are each independently hydrogen, fluorine, chlorine, a (perfluoro)alkyl group having 1 to 3 carbon atoms, or a (perfluoro)alkenyl group; A.sup.3 and A.sup.4 are each independently hydrogen, fluorine, or chlorine; at least one of A.sup.1 to A.sup.6 is hydrogen; at least one of A.sup.1 to A.sup.6 is fluorine or chlorine] comprises a step of subjecting the same or different halogenated olefin(s) represented by formula (2): A.sup.7A.sup.8C═CA.sup.9X [A.sup.7 and A.sup.8 are each independently hydrogen, fluorine, chlorine, a (perfluoro)alkyl group having 1 to 3 carbon atoms, or a (perfluoro)alkenyl group; A.sup.9 is each independently hydrogen, fluorine, or chlorine; X is bromine or iodine] to a coupling reaction in the presence of a zero-valent metal and a metal salt.