... III) and Tetrafluoro- allene (IV).-1,3-Dibromo-l,1,3,3-tetrafluoropropane (11) was prepared from 1,ldifluoroethylene and dibromodiikoro- methane23 as described by Tarrant, et a1.8 ... It was used without further purification for the preparation of the al- lene. ... (28) M. Hauptschein, C. S ...