NOVELTY - Preparation of acyl fluoride compounds (III) comprises preparing fluorosulfate compounds (I) by reacting fluorosulfuric acid pentafluoroallyl ester (a) with at least one hypofluorite compounds (II); and converting (I) to (III).    USE - (III) are useful as intermediate for preparing hypofluorite compounds (VIII-A) and (VIII-B), and haloether compounds (VIA) and (VI-B), which are useful for preparing vinyl ether compounds (VII-A) and (VII-B) (all claimed). The haloether compounds (VIA) and (VI-B) are useful for preparing fluorovinyl ether compounds (IX-A) and (IX-B), which are useful as monomers/comonomers for manufacturing polymers. (IX-A) is useful for the manufacture of: (per)fluorinated ionomers to produce membranes (e.g. for electrochemical cells or fuel cells); and (per)fluoroelastomers. (IX-B) is useful for manufacturing thermoplastic (per)fluoropolymers to modify tetrafluoro ethylene-based polymers.    ADVANTAGE - (I-A) and (I-B) can be produced with high selectivity. The process provides (III) in a one-step procedure, with high yield. (IX-A) can be easily obtained from haloether compounds (VIA). The hypofluorite compounds can be added to the double bond of (a) without incepting nucleophilic reactions on the fluorosulfate moiety.    DETAILED DESCRIPTION - Preparation of acyl fluoride compounds (III) of formulae (R1f-O-CF2-CF2-C(=O)-F) (III-A) and (III-B) comprises preparing fluorosulfate compounds (I) of formulae (R1f-O-CF2-CF2-CF2-O-SO2-F) (I-A) and (I-B) by reacting fluorosulfuric acid pentafluoroallyl ester (a) with at least one hypofluorite compounds (II) of formula (R1f-OF) (II-A) and (FO-R1fa-OF) (II-B); and converting (I-A) and (I-B) to (III-A) and (III-B).    R1f = monovalent 1-20C fluorocarbon (optionally comprising oxygen catenary atoms, and functional groups comprising heteroatoms (e.g. -SO2F));    R1fa = divalent 1-6C fluorocarbon, preferably -C(X1)(X2)-; and    X1, X2 = F or 1-3C fluorocarbon.    INDEPENDENT CLAIMS are included for:    (1) fluorovinyl ether compounds of formulae (R2f-O-CF2-CF2-CF2-O-CF=CF2) (IX-A) and (IX-B); and    (2) polymers comprising recurring units derived from compounds (IX-A) and (IX-B).    R2f = -CF2-CF2-SO2F, -C2F5, -(CF2)2-CF3 or -CF2-COOCH3;    R2fa = -CX1aX2a-; and    X1a, X2a = -F or -CF3.