Crystal and molecular structure of 1,1,2-trifluorobuta-1,3-diene

A single crystal of 1,1,2-trifluorobuta-1,3-diene, m.p. –108°C, was obtained by in situ crystallization in a capillary directly on a diffractometer. 1,1,2-Trifluorobutadiene crystallizes monoclinic, space group Pc, a = 4.4030(12), b = 6.4160(16), c = 8.293(3) Å, = 91.728(14)°, V = 234.17(12) Å, d _calc = 1.5326 g cm^–3, Z = 2, wR ₂ = 0.1332. The 1,1,2-trifluorobutadiene molecules have an anti conformation, C4–C3–C2–C1 179.17(1)°. There is no fluorine substitution effect on the bond lengths of the conjugated C–C double bonds, C1–C2 1.331(3), C3–C4 1.336(4) Å. The central bond C2–C3 1.436(4) Å is shorter than a single bond because of conjugation. The C–F bond lengths of the CF₂ group are significantly shorter than the one of the CF moiety.