1 ES8 [(9h-fluoren-9-ylideneamino)oxy]acetic acid 1.000 2 5JW {[(2,7-dichloro-9h-fluoren-9-ylidene)amino]oxy}acetic acid 0.905 3 L32 {[(2,7-dibromo-9h-fluoren-9-ylidene)amino]oxy}acetic acid 0.905 4 7BD 3-[(9h-fluoren-9-ylideneamino)oxy]propanoic acid 0.773 5 6BD (2s)-3-[(9h-fluoren-9-ylideneamino)oxy]-2-methylpropanoic acid 0.739