| 摘要 |
The present invention relates to the compounds cis-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile and trans-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile and to a process for their preparation. The process relates to the preparation of cis-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile and trans-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile or optionally one of these two compounds, by fractionally distilling a mixture containing cis- and trans-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile under reduced pressure, separating off a main fraction containing at least 80% by weight of cis-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile and a main fraction containing at least 80% by weight of trans-4-(2,2,3,3-tetrafluoropropoxy)cinnamonitrile, further purifying these main fractions by means of fractional crystallization or 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 and returning the remaining fractions to the process directly or after isomerization.
|
