Röntgeneinkristallstrukturanalyse eines Chlorderivates von Permanentrot FRLL. Vergleich mit dem entsprechenden Derivat von Permanentbraun FG

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Abstract
The crystal structure of 1-(2,5-dichlorophenylazo)-2-hydroxy-3-naphthoic acid 4-chloro-2-methoxy-anilide (C24H16Cl3N3O3) has been determined by x-ray methods. The structure has been refined to an R value of 8.04% with 2194 unique reflections. The crystals belong to the space group P212121 with a = 16.445(7), b = 4.592(4) and c = 28.493(8) Å and with 4 molecules in the unit cell. In the crystal the molecule exists as the hydrazone tautomer; the molecule is planar and its hydrogen bonds are solely intramolecular. The widest angle between the least-squares planes of the various atomic arrangements and the least-squares plane of the molecule is 2.4° and the longest distance of an atom from this plane is 0.188 Å.A molecule investigated earlier by us has another methoxy group in the anilide-ring. This makes such a large steric hindrance that the planes of the various atomic arrangements form much wider angles, the largest being 18.4°. This may be the reason that the two molecules have a different colour in the solid state (red resp. brown). In non-polar solvents the two compounds have the same colour. Therefore there must be another conformation. A possibility is that the anilide ring is rotated with respect to the rest of the molecule.

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