The structures assigned by earlier investigators to the difluorides produced by the addition of fluorine to 1, ldiphenylethylene and 1, l-diphenyl-1-propene have been shown to be incorrect; actually, the isomeric rearrangement products, a, a-difluorobibenzyl (VI) and l, l- difluoro-1, 2-diphenylpropane (XIII), respectively, are formed. I t has been found that 1, l- diphenylethylene also undergoes additive dimerization on fluorination with lead tetra. ...