(1,1'-Biphenyl)-4-butanoic acid, 2',4'-difluoro-alpha-methylene-gamma-oxo- 161692-81-5 2',4'-Difluoro-alpha-methylene-gamma-oxo-(1,1'-biphenyl)-4-butanoic acid 4-(2',4'-Difluorobiphenyl-4-yl)-2-methylene-4-oxobutanoic acid