(1,1'-Biphenyl)-4-butanoic acid, 2',4'-difluoro-beta-methylene-gamma-oxo- 170950-54-6 2',4'-Difluoro-beta-methylene-gamma-oxo-(1,1'-biphenyl)-4-butanoic acid 4-(2',4'-Difluorobiphenyl-4-yl)-3-methylene-4-oxobutanoic acid