Ethyl 3-oxo-2-(2-phenylhydrazinylidene)butanoate: a re-determination

The previous crystallographic studies [Wang et al. (2005 ▶). Huaxue Yanjiu 16, 29–32; Wang et al. (2007 ▶). Youji Huaxue, 27, 524] of the title compound, C12H14N2O3, gave only the unit-cell dimensions and an R factor with no other details available: the full structure is presented here. The ethoxy group is disordered over two orientations with refined occupancies of 0.642 (15):0.358 (15). The nine C atoms and two N atoms of the 1-phenyl-2-(propan-2-ylidene)hydrazine segment of the molecule are close to being coplanar, with a maximum deviation of 0.0779 (14) Å for the phenylamino N atom and an intramolecular N—H⋯O hydrogen bond generates an S(6) ring. In the crystal, pairs of C—H⋯O hydrogen bonds link molecules into inverson dimers, generating R 2 2(16) loops.

The previous crystallographic studies [Wang et al. (2005). Huaxue Yanjiu 16, 29-32; Wang et al. (2007). Youji Huaxue, 27, 524] of the title compound, C 12 H 14 N 2 O 3 , gave only the unit-cell dimensions and an R factor with no other details available: the full structure is presented here. The ethoxy group is disordered over two orientations with refined occupancies of 0.642 (15):0.358 (15). The nine C atoms and two N atoms of the 1-phenyl-2-(propan-2-ylidene)hydrazine segment of the molecule are close to being coplanar, with a maximum deviation of 0.0779 (14) Å for the phenylamino N atom and an intramolecular N-HÁ Á ÁO hydrogen bond generates an S(6) ring. In the crystal, pairs of C-HÁ Á ÁO hydrogen bonds link molecules into inverson dimers, generating R 2 2 (16) loops.

Related literature
For previous reports of the structure of the title compound, see: Wang et al. (2005Wang et al. ( , 2007. For further synthetic details, see: Fernandes et al. (1975). For graph-set analysis of hydrogen bonding, see: Bernstein et al. (1995 Table 1 Hydrogen-bond geometry (Å , ).

Comment
The unit cell of the title compound, (I), was reported by Wang et al. (2005Wang et al. ( , 2007. In the full structure reported here, the ethoxy group is disordered over two orientations with refined occupancies 0.642 (15) hydrogen bonds link pairs of molecules into centrosymmetric dimers generating R 2 2 (16) rings (Bernstein et al., 1995).

Experimental
The title compound was prepared by the coupling of diazonium salt of aniline with ethyl acetoacetate (Fernandes et al., 1975). It was recrystalized from methanol by slow evaporation at room temperature to yield colourless blocks of (I).

Refinement
High values of isotropic thermal parameters for atoms O3 and C10 and unacceptable bond lengths for O3-C10 and C10-C11 of the ethoxy group indicated possible disorder. A difference elctron density map excluding the atoms O3, C10 and C11 showed that the ethoxy group to be disordered over two sites. The ratio of the occupancy factors of the two disorder components refined to 0.642 (15):0.358 (15). All H-atoms were positioned geometrically and refined using a riding model with d(C-H) = 0.93Å, U iso =1.2U eq (C) for aromatic 0.97Å, U iso = 1.2U eq (C) for CH 2 , 0.86Å, U iso = 1.2U eq (N) for NH, and 0.96Å, U iso = 1.5U eq (C) for CH 3 atoms.

Special details
Geometry. All su's are estimated using the full covariance matrix. The cell su's are taken into account individually in the estimation of su's in distances, angles and torsion angles; correlations between su's in cell parameters are only used when they are defined by crystal symmetry.
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 Rfactors(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.