N,N′-(Propane-1,3-diyl)bis(2-aminobenzamide)

The title compound, C17H20N4O2, was prepared by the reaction between 1,3-diaminopropane and isatoic anhydride in water. The carbonyl O atoms are involved in intramolecular hydrogen bonding with the amine group and intermolecular hydrogen bonding with an amide H atom of an adjacent molecule. In the crystal, pairs of N—H⋯O hydrogen bonds link molecules into inversion dimers and further N—H⋯O hydrogen bonds link the dimers into ladder-like chains along the a axis.

The title compound, C 17 H 20 N 4 O 2 , was prepared by the reaction between 1,3-diaminopropane and isatoic anhydride in water. The carbonyl O atoms are involved in intramolecular hydrogen bonding with the amine group and intermolecular hydrogen bonding with an amide H atom of an adjacent molecule. In the crystal, pairs of N-HÁ Á ÁO hydrogen bonds link molecules into inversion dimers and further N-HÁ Á ÁO hydrogen bonds link the dimers into ladder-like chains along the a axis.

Gundapaneni Comment
The reactions of isatoic anhydride with amines have been very interesting and yield molecules with amine and amide functional groups (Clark et al., 1944). We have adopted the reaction of isatoic anhydride with different diamines to obtain a good number of organic molecules having two amine and two amide groups (Swamy & Kumar, 1996;Swamy et al., 2003;2004). The N,N′-propyl-bis-(2-aminobenzamide) I was prepared by the reaction between isatoic anhydride and 1,3-diaminopropane (Swamy & Kumar, 1996). We recrystallized I from water/methanol mixture to obtain block shaped single crystals. Herein we report the molecular and crystal structures of the title compound. The molecular structure of I is shown in Fig. 1 and the packing diagram with inter-and intra-molecular H-bonds resulting in supramolecular assembly and the formation of ladder like chain is shown in Fig. 2. The carbonyl oxygen is involved in the formation of intramolecular H-bond with amine hydrogen and intermolecular H-bond with amide hydrogen of the adjacent molecule.
These intermolecular H-bonds lead to the formation of ladder like chain as shown in Fig. 2.

Experimental
The title compound was synthesized by adding 1.15 mg of 1,3-diamminopropane (12.25 mmol) in 15 ml water to 4.0 mg of isatoic anhydride (24.5 mmol) with continuous stirring. Effervescence was observed while warming the reaction mixture on water bath that ceased after one hour. Microcrystalline solid product was obtained on allowing the mixture to stand overnight. The product was purified and recrystallized from methanol / water mixture to obtain block shaped crystals, m.p. 341 K.

Refinement
The H atoms based on C atoms were positioned geometrically with C-H = 0.93Å for aromatic H and C-H = 0.97Å for methylene H, refined using a riding model with U iso (H) = 1.2U eq (C). The H atoms based on N atoms were found from difference Fourier map and refined freely.  The molecular structure of title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are presented as a small spheres of arbitrary radius.

Figure 2
The formation of centrosymmetrical dimers by classical H bonds (N-H···O type) in crystal structure of title compound -

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 > 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.  (9) 0.0065 (7) 0.0099 (7) 0.0033 (7)  C13 0.0529 (9) 0.0410 (9) 0.0457 (9) 0.0079 (7) 0.0072 (7) 0.0075 (7)