Provided is a method of producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane, the method having a dimer reaction step of reacting a trifluoropyruvic acid fluoride dimer with hexafluoropropylene oxide in an organic solvent in the presence of one or more fluorides selected from the group consisting of potassium fluoride and sodium fluoride to obtain perfluoro(dimethyl-2-oxo-1,4-dioxane).

Provided is a method of producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane, the method having a dimer reaction step of reacting a trifluoropyruvic acid fluoride dimer with hexafluoropropylene oxide in an organic solvent in the presence of one or more fluorides selected from the group consisting of potassium fluoride and sodium fluoride to obtain perfluoro(dimethyl-2-oxo-1,4-dioxane).

Provided is a method of manufacturing a trifluoropyruvyl fluoride dimer, including a reaction step of reacting hexafluoropropylene oxide and aldehyde.

Provided is a method of manufacturing a trifluoropyruvyl fluoride dimer, including a reaction step of reacting hexafluoropropylene oxide and aldehyde.

The present invention provides a nonaqueous electrolytic solution capable of improving electrochemical characteristics in the case of using an energy storage device at a high temperature and at a high voltage and further capable of inhibiting the gas generation while maintaining a capacity retention rate after storage at a high temperature and at a high voltage and also provides an energy storage device using the same. Disclosed is a nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent, the nonaqueous electrolytic solution containing a carboxylic acid ester compound represented by the following general formula (I). ##STR00001## In the formula, each of R.sup.1 and R.sup.2 independently represents a hydrogen atom, a —C(═O)—OR.sup.4 group, or the like, and R.sup.1 and R.sup.2 may be bonded to each other to form a ring structure. R.sup.3 represents a hydrogen atom or the like, and n represents an integer of 1 to 3. When n is 1, then L and R.sup.4 represent an alkyl group having 1 to 6 carbon atoms or the like; and when n is 2 or 3, then L represents an n-valent connecting group, X represents a —C(═O)— group, an —S(═O)— group, an —S(═O).sub.2— group, an —S(═O).sub.2—R.sup.5—S(═O).sub.2— group or a CR.sup.6R.sup.7 group, R.sup.5 represents an alkylene group having 1 to 4 carbon atoms, and each of R.sup.6 and R.sup.7 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

The present invention provides a nonaqueous electrolytic solution capable of improving electrochemical characteristics in the case of using an energy storage device at a high temperature and at a high voltage and further capable of inhibiting the gas generation while maintaining a capacity retention rate after storage at a high temperature and at a high voltage and also provides an energy storage device using the same. Disclosed is a nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent, the nonaqueous electrolytic solution containing a carboxylic acid ester compound represented by the following general formula (I). ##STR00001## In the formula, each of R.sup.1 and R.sup.2 independently represents a hydrogen atom, a —C(═O)—OR.sup.4 group, or the like, and R.sup.1 and R.sup.2 may be bonded to each other to form a ring structure. R.sup.3 represents a hydrogen atom or the like, and n represents an integer of 1 to 3. When n is 1, then L and R.sup.4 represent an alkyl group having 1 to 6 carbon atoms or the like; and when n is 2 or 3, then L represents an n-valent connecting group, X represents a —C(═O)— group, an —S(═O)— group, an —S(═O).sub.2— group, an —S(═O).sub.2—R.sup.5—S(═O).sub.2— group or a CR.sup.6R.sup.7 group, R.sup.5 represents an alkylene group having 1 to 4 carbon atoms, and each of R.sup.6 and R.sup.7 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

Provided herein are perfluoro copolymers of a perfluoro dioxole monomer, a perfluoro dioxane monomer, and an optional perhalo monomer. Methods of making the perfluoro copolymers and methods of using the perfluoro copolymers are also disclosed.

Provided herein are perfluoro copolymers of a perfluoro dioxole monomer, a perfluoro dioxane monomer, and an optional perhalo monomer. Methods of making the perfluoro copolymers and methods of using the perfluoro copolymers are also disclosed.

Provided is a method of stabilizing a perfluorodioxolane compound, which includes having a quinone compound present in a composition containing a perfluorodioxolane compound, wherein the perfluorodioxolane compound is one or more perfluorodioxolane compounds selected from the group consisting of a perfluorodioxolane compound denoted by general formula (1) and a perfluorodioxolane compound denoted by general formula (2).

##STR00001##

Provided is a method of stabilizing a perfluorodioxolane compound, which includes having a quinone compound present in a composition containing a perfluorodioxolane compound, wherein the perfluorodioxolane compound is one or more perfluorodioxolane compounds selected from the group consisting of a perfluorodioxolane compound denoted by general formula (1) and a perfluorodioxolane compound denoted by general formula (2).

##STR00001##