N 2,N 2′-Bis(2,2-dimethylpropanoyl)benzene-1,3-dicarbohydrazide

In the molecular structure of the title hydrazide derivative, C18H26N4O4, the conformations of the two units of 2-(2,2-dimethyl-1-oxopropyl)hydrazide substituents are not planar; these two units are attached axially to the benzene ring with C(ortho)—C—C(=O)—N torsion angles of 28.1 (2) and 31.0 (2)° [where C(ortho) is the C atom at position 4 of the benzene ring relative to the substituent at position 3 or the C atom at position 6 of the benzene ring relative to the substituent at position 1, as appropriate]. The dihedral angles between the hydrazide units and the benzene ring are 62.66 (7) and 63.84 (7)°. In the crystal structure, molecules are arranged in an anti-parallel manner and are linked by N—H⋯O intermolecular hydrogen bonds and weak C—H⋯O intermolecular interactions into a three-dimensional network. The structure is further stabilized by a weak C—H⋯N intramolecular interaction.

In the molecular structure of the title hydrazide derivative, C 18 H 26 N 4 O 4 , the conformations of the two units of 2-(2,2dimethyl-1-oxopropyl)hydrazide substituents are not planar; these two units are attached axially to the benzene ring with C(ortho)-C-C( O)-N torsion angles of 28.1 (2) and 31.0 (2) [where C(ortho) is the C atom at position 4 of the benzene ring relative to the substituent at position 3 or the C atom at position 6 of the benzene ring relative to the substituent at position 1, as appropriate]. The dihedral angles between the hydrazide units and the benzene ring are 62.66 (7) and 63.84 (7) . In the crystal structure, molecules are arranged in an anti-parallel manner and are linked by N-HÁ Á ÁO intermolecular hydrogen bonds and weak C-HÁ Á ÁO intermolecular interactions into a three-dimensional network. The structure is further stabilized by a weak C-HÁ Á ÁN intramolecular interaction.

Experimental
Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2; data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 1998); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003). Hydrazide derivatives of different compounds are very important units in host-guest chemistry due to their special arrangement of donor-acceptors (Feng et al., 2006;Yang et al., 2007). These types of compounds are also important for the metal coordinations and related studies (Hołtra et al., 2007;Nica et al., 2007;Raveendran & Pal, 2007). Hydrazidebased compounds are also involved in different synthetic applications (Fernández et al., 2004;Lemay et al., 2007;Kim et al., 2007;Rivero & Buchwald, 2007) as well as in medicinal activities (Imramovský et al., 2007;Liu et al., 2006;Sicardi et al., 1980). We synthesized the title compound for being a host of host-guest complexes syntheses. The single-crystal X-ray structural study of the title compound was undertaken in order to establish the three-dimensional structure and to gain more details of conformations of the various groups.
In the crystal packing in Fig. 2, the molecules are arranged in an anti-parallel manner and linked by N-H···O intermolecular hydrogen bonds and weak C-H···O intermolecular interactions (Table 1) into three dimensional networks. The crystal is further stabilized by a weak C-H···N intramolecular interaction.

S2. Experimental
Initially isophthalic acid was converted to its methyl ester under refluxing condition with methanol and a catalytic amount of concentrated sulfuric acid. This ester was then refluxed with excess hydrazine hydrate and ethanol for three hours. After completion of the reaction, excess ethanol was evaporated out and the solid substance was washed well with water and dried under reduced pressure. The properly dried intermediate compound was treated with pivalic anhydride at 353 K for seven hours. The crude compound was extracted with chloroform after neutralizing the reaction mixture with aqueous sodium bicarbonate solution. The title compound was purified by column chromatography (Silica gel 100-200 mesh) using ethyl acetate as eluent to afford an off-white colored solid compound. Single crystals were grown by slow evaporation of CHCl 3 /MeOH solution (v/v 1:1) (m.p. over 523 K).

S3. Refinement
Hydrazide H atoms were located in a difference map and isotropically refined. The remaining H atoms were positioned geometrically and refined using a riding model with C-H = 0.93 Å for aromatic and 0.96 Å for CH 3 . The U iso values were constrained to be 1.5U eq of the carrier atom for methyl H atoms and 1.2U eq for the remaining H atoms. A rotating group model was used for the methyl groups.

Figure 1
The molecular structure of the title compound, showing 50% probability displacement ellipsoids and the atomic numbering.

Figure 2
The crystal packing of the title compound. Hydrogen bonds were shown as dash lines.

sup-3
Acta Cryst. (2008). E64, o175-o176 where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.46 e Å −3 Δρ min = −0.28 e Å −3 Special details Experimental. The data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. 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.