A method for improving preservation stability of 2,2-difluoroacetaldehyde according to the present invention include at least: a first step of forming a 2,2-difluoroacetaldehyde-alcohol composite system in which a 2,2-difluoroacetaldehyde hemiacetal coexists with an excess alcohol, wherein the total molar amount of the alcohol is 1.15 to 4.00 times the total molar amount of 2,2-difluoroacetaldehyde; and a second step of storing, in a storage container, the 2,2-difluoroacetaldehyde-alcohol composite system formed in the first step. It is possible by this method to suppress the conversion of the 2,2-difluoroacetaldehyde hemiacetal to a dimer and maintain the original aldehyde activity of the target compound with less composition change over a long term.

A method for improving preservation stability of 2,2-difluoroacetaldehyde according to the present invention include at least: a first step of forming a 2,2-difluoroacetaldehyde-alcohol composite system in which a 2,2-difluoroacetaldehyde hemiacetal coexists with an excess alcohol, wherein the total molar amount of the alcohol is 1.15 to 4.00 times the total molar amount of 2,2-difluoroacetaldehyde; and a second step of storing, in a storage container, the 2,2-difluoroacetaldehyde-alcohol composite system formed in the first step. It is possible by this method to suppress the conversion of the 2,2-difluoroacetaldehyde hemiacetal to a dimer and maintain the original aldehyde activity of the target compound with less composition change over a long term.

This disclosure is directed to methods of preparing organic aldehydes, each method comprising contacting a terminal olefin with an oxidizing mixture comprising: (a) a dichloro-palladium complex; (b) a copper complex; (c) a source of nitrite;
under aerobic reaction conditions sufficient to convert at least a portion of the terminal olefin to an aldehyde.

This disclosure is directed to methods of preparing organic aldehydes, each method comprising contacting a terminal olefin with an oxidizing mixture comprising: (a) a dichloro-palladium complex; (b) a copper complex; (c) a source of nitrite;
under aerobic reaction conditions sufficient to convert at least a portion of the terminal olefin to an aldehyde.

A polyimide which is obtained by a reaction of an aromatic diamine having a 1,1,1-trifluoro-2,2-ethanediyl group (C(CF.sub.3)H), as a linkage skeleton, with a tetracarboxylic dianhydride is easily dissolved in an organic solvent and exhibits excellent film forming properties. In addition, the thus-obtained polyimide can be used for an optical film and a display device.

A polyimide which is obtained by a reaction of an aromatic diamine having a 1,1,1-trifluoro-2,2-ethanediyl group (C(CF.sub.3)H), as a linkage skeleton, with a tetracarboxylic dianhydride is easily dissolved in an organic solvent and exhibits excellent film forming properties. In addition, the thus-obtained polyimide can be used for an optical film and a display device.

The present invention has the effect of making it possible to produce 1,1,1-trifluoro-2,2-bisarylethane efficiently by a simple procedure by condensing a mixture of fluoral and hydrogen fluoride with an aryl compound under anhydrous conditions. The purity of the 1,1, 1-trifluoro-2, 2-bisarylethane obtained can be raised by a simple purification method such as crystallization or distillation. The obtained 1,1,1-trifluoro-2,2-bisarylethane can be increased in purity by a simple purification method such as crystallization operation or distillation.

The present invention has the effect of making it possible to produce 1,1,1-trifluoro-2,2-bisarylethane efficiently by a simple procedure by condensing a mixture of fluoral and hydrogen fluoride with an aryl compound under anhydrous conditions. The purity of the 1,1, 1-trifluoro-2, 2-bisarylethane obtained can be raised by a simple purification method such as crystallization or distillation. The obtained 1,1,1-trifluoro-2,2-bisarylethane can be increased in purity by a simple purification method such as crystallization operation or distillation.