Concomitant colour polymorphs of (Z)-N-(4-fluorophenyl)-2-oxopropanehydrazonoyl chloride

Abstract

The title com­pound, (Z)-N-(fluoro­phen­yl)-2-oxo­propane­hydrazonoyl chloride, C9H8ClFN2O, was found to form concomitant colour polymorphs upon recrystallization from acetone. Block-shaped pale-orange crystals of form I (space group P21/n, No. 14) and prism-shaped yellow crystals of form II (space group P21/c, No. 14) both belong to the monoclinic crystal system. N—H⋯O hy­dro­gen bonds resulting in zigzag chains [graph-set descriptor C(6)] are the dominating inter­molecular inter­actions in both crystal forms. The hy­dro­gen-bonded zigzag chains so formed extend by 21 screw symmetry in form I and by c-glide symmetry in form II, and are arranged in layers, which are more corrugated in form II than in form I. The polymorphs are virtually indistinguishable by their calculated densities, packing indices and melting points. Form I sublimes to yield crystals of form II, whereas form II sublimes to afford crystals of the same polymorph with characteristic crystal morphology.