2,2,3-trifluoropropionyl fluoride is prepared by opening the ring of tetrafluorooxetane in the presence of a catalyst. Analogously, a novel 2,2-difluoropropionic acid derivative of the formula: XCH.sub.2 CF.sub.2 COY (I) wherein X is chlorine, bromine, iodine, a group of the formula: R.sub.1 O-- (II) or R.sub.2 COO-- (III) wherein R.sub.1 R.sub.2 are each an aliphaic or halogenated aliphatic hydrocarbon group having 1 to 8 carbon atoms or an aromatic hydrocarbon group having 6 to 8 carbon atoms optionally bearing at least one substituent, or a group of the formula: X'CH.sub.2 CF.sub.2 CF.sub.2 O-- (IV) wherein X' is fluorine, chlorine, bromine, iodine, the group of the formula: R.sub.1 O--or R.sub.2 COO--; and Y is fluorine or a group of the formula: --OR.sub.3 (V) wherein R.sub.3 is an aliphatic or halogenated aliphatic hydrocarbon group having 1 to 8 carbon atoms except a perfluorohydrocarbon group or an aromatic hydrocarbon group having 6 to 8 carbon atoms optionally bearing at least one substituent or of the formula : --OCH.sub.2 R.sub.f (V') wherein R.sub.f is an aliphatic perfluorohydrocarbon having 1 to 7 carbon atoms is prepared.
                            2,2,3-三
氟丙酰
氟是在催化剂存在下打开四
氟氧杂环的环来制备的。类似地,通过以下式子的新型
2,2-二氟丙酸衍
生物制备:XCH.sub.2 CF.sub.2 COY (I),其中X为
氯、
溴、
碘、式:R.sub.1 O-- (II)或R.sub.2 COO-- (III)的基团,其中R.sub.1和R.sub.2均为具有1至8个碳原子的脂肪或
卤代脂肪烃基或具有6至8个碳原子的
芳香烃基,可选地带有至少一个取代基,或式:X'CH.sub.2 CF.sub.2 CF.sub.2 O-- (IV)的基团,其中X'为
氟、
氯、
溴、
碘、式:R.sub.1 O--或R.sub.2 COO--;Y为
氟或式:--OR.sub.3 (V)的基团,其中R.sub.3为具有1至8个碳原子的脂肪或
卤代脂肪烃基,但不包括
全氟碳氢基团或具有6至8个碳原子的
芳香烃基,可选地带有至少一个取代基,或式:--OCH.sub.2 R.sub.f (V'),其中R.sub.f为具有1至7个碳原子的脂肪
全氟碳氢基团来制备。