4-(2-Chlorophenylamino)-pent-3-en-2-one

In the title compound, C11H12ClNO, intramolecular N—H⋯O hydrogen bonding is present. The dihedral angle between the benzene ring and the pentenone unit is 46.52 (5)°. In the crystal, C—H⋯O interactions between hydrogen atoms of the aryl moiety and two separate oxygen atoms occur, leading to a three-dimensional network.

Financial assistance from the University of the Free State is gratefully acknowledged. We also express our gratitude towards SASOL, the South African National Research Foundation (SA-NRF/THRIP) and the Inkaba yeAfrica initiative for financial support of this project. Part of this material is based on work supported by the SA-NRF/THRIP under grant No. GUN 2068915. Opinions, findings, conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the SA-NRF.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: PK2444).

4-(2-Chlorophenylamino)-pent-3-en-2-one Gertruida J.S. Venter, Alice Brink, Gideon Steyl and Andreas Roodt Comment
The β-diketone compound AcacH (acetylacetone; or when coordinated acetylacetonato, acac -) has been studied extensively, with a multitude of derivatives synthesized to date. One such derivative type, known as enaminoketones, contains both nitrogen and oxygen atoms with an unsaturated C═C bond, and is of interest in various fields including liquid crystals [Pyżuk et al. (1993)

Experimental
A solution of acetylacetone (11.07 g, 0.1106 mol), 2-chloro-aniline (10.73 g, 0.1008 mol) and 2 drops of H 2 SO 4 (conc.) in 150 ml benzene was refluxed for 6 h in a Dean-Stark trap, filtered and left to crystallize. Crystals suitable for X-ray diffraction were obtained in 17.86 g (94.32%) yield. This compound is stable in air and light over a period of several months.

Refinement
The methyl and aromatic H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H = 0.95 Å and 0.98 Å and U iso (H) = 1.5U eq (C) and 1.2U eq (C), respectively. The methyl groups were generated to fit the difference electron density and the groups were then refined as rigid rotors.

Computing details
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT-Plus (Bruker, 2004); data reduction: SAINT-Plus (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: WinGX (Farrugia, 1999  Partially filled unit cell illustrating the intra-and intermolecular hydrogen bonding interactions in the title compound, indicated with dashed lines. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.013 Δρ max = 0.21 e Å −3 Δρ min = −0.24 e Å −3 Absolute structure: Flack (1983), 932 Friedel pairs Flack parameter: 0.01 (5) Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.