The crystal structure of C.I. Pigment Yellow 3, α-(1-hydroxyethylidene)-2-chloro-acetanilide-α-azo-(4′-chloro-2′-nitrobenzene)

Abstract

Abstract The crystal structure of C.I. Pigment Yellow 3, α-(1-hydroxyethylidene)-2-chloro-acetanilide-α-azo-(4′-chloro-2′-nitrobenzene) has been determined by single-crystal X-ray diffraction techniques. It crystallises in the orthorhombic system with cell parameters a = 13.240 ± 0.073 Å, b = 30.206 ± 0.118 Å, c = 8.333 ± 0.025 Å. The space group is Pbca and there are eight molecules per unit cell. The structure was solved using direct methods and least-squares refinement has been completed on three-dimensional data, 1191 reflections (CuKα radiation). The hydrogen atoms have been found and included, but only those associated with the methyl group have been refined. The final residual is 7.2%. The molecule exists as the hydrazone tautomer and intramolecular hydrogen bonds keept the molecule approximately planar. The molecules are packed in planar chains parallel to the c axis with the molecules linked by hydrogen bonds, alternatively they may be thought of as packed in columns parallel to the a axis with alternate molecules antiparallel but with the molecules linked by van der Waals forces.