Cis-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile and trans-4(2,2,3,3-tetrafluoropropoxy)cinnamonitrile and their production

PROBLEM TO BE SOLVED: To obtain an essentially and isomerically pure form of new 4-(2,2,3,3- tetrafluoropropoxy)cinnamic acid derivative and to provide a simple and efficient method for preparing the same. SOLUTION: This method for producing cis and trans 4-(2,2,3,3- tetrafluoropropoxy)cinnamonitrile or either one of them, is provided by fractionally distilling the mixture containing 4-(2,2,3,3-tetrafluoropropoxy)cinnamonitriles under a reduced pressure for separating off a main fraction containing at least 80 wt.% of cis-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile and a main fraction containing at least 80 wt.% of trans 4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile, further purifying these main fractions by means of a fractional crystallization or a melt crystallization. or adjusting one of these main fractions by isomerization to the cis/trans isomer ratio corresponding to the particular thermodynamic equilibrium and returning it to the process a and returning the remaining fractions to the process directly or after the isomerization. COPYRIGHT: (C)1996,JPO