FC-4  Perfluorobutanesulfonyl fluoride
Structure formula: CF₃CF₂ CF₂CFSO₂F

Molecular formula: n- C₄F₉SO₂F

Molecular Structure:

CAS No. 375-72-4

Appearance: clear colorless or slightly yellow liquid

Boiling point: 65-66?C

Refractive index(n²⁵_D): 1.2810

Density (d₄²⁰): 1.750-1.700

Assay: 95% ( Chromatographic analysis)

PH: 3.8-4.8

 Physical properties:

Insoluble in water, it can hydrolyze in alkali to produce nonafluorobutanesulfo salt, then acidize to obtain nonafluorobutanesulfonic acid.

Application: its properties is similar to perfluorooctanesulfonyl fluoride, it can be used to synthesize multi-kind of fluoro surfactant, its Potassium salt C₄F₉SO₂K is a very good anion surfactant, also a best fire retardant for polycarbonate.