(E)-2-(4-Chlorophenoxy)-N′-(pyridin-4-ylmethylidene)acetohydrazide

In the title compound, C14H12ClN3O2, the acylhydrazone base [C(=O)—N—N=C] is essentially planar, with an r.m.s. deviation of 0.0095 Å, and makes a dihedral angle of 12.52 (10)°with the pyridine ring. In the crystal, molecules are linked via pairs of N—H⋯O hydrogen bonds, forming inversion dimers with an R 2 2(8) graph-set motif. The dimers are linked via C—H⋯π interactions forming chains along [101].

In the title compound, C 14 H 12 ClN 3 O 2 , the acylhydrazone base [C( O)-N-N C] is essentially planar, with an r.m.s. deviation of 0.0095 Å , and makes a dihedral angle of 12.52 (10) with the pyridine ring. In the crystal, molecules are linked via pairs of N-HÁ Á ÁO hydrogen bonds, forming inversion dimers with an R 2 2 (8) graph-set motif. The dimers are linked via C-HÁ Á Á interactions forming chains along [101]. For graph-set motifs, see: Etter et al. (1990) and for classification of hydrogen bonds, see: Gilli & Gilli (2009 Table 1 Hydrogen-bond geometry (Å , ).

Experimental
The synthesis of the title structure proceeded in three steps.
First, concentrated H 2 SO 4 (98 weight %, 1.4 ml) was added slowly while stirring to a mixture of 4-chlorophenoxyacetic acid (11.2 g, 0.06 mol) in ethanol (99.7 volume %, 120 ml). The mixture was left to reflux for 6 h at 359 K. Then 34.2 ml of 98.5 weight % of tris(2-hydroxyethyl)amine (trolamine) were added dropwise into the mixture while stirring in order to neutralize the mixture. Then the ethanol in the mixture was removed by reduced pressure distillation (335 K, about 0.003 MPa). What has left was poured into 100 ml of water heated to 321 K. The white precipitate (12.21 g) of ethyl(4chlorophenoxy)acetate was filtered and washed.
Finally, the title compound was synthesized by adding 4-pyridinecarboxaldehyde (5 ml) slowly to a mixture of 2-(4chlorophenoxy) acetohydrazide in ethanol (99.7 volume %, 20 ml) and water (15 ml) while stirring. Then the mixture was refluxed for 3.5 h at room temperature. Prismatic colourless crystals with the size about that of the used sample formed in 24 h.

Refinement
All the hydrogen atoms were identified in the difference electron density map, nevertheless the aryl and methylene H atoms were situated into idealized positions and constrained to ride on their parent atoms with C-H = 0.93 and 0.97 Å for aryl and methylene H atoms, respectively, with U iso (H aryl / methylene ) = 1.2U eq (C aryl / methylene ). The positional parameters of supplementary materials sup-2 Acta Cryst. (2013). E69, o28 the secondary amine H atom were refined freely while its isotropic displacement parameter was constrained as 1.2 multiple of the equivalent isotropic parameter of its carrier atom.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > σ(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.