Crystal structure of (1Z,2E)-cinnamaldehyde oxime

The title compound, C9H9NO, crystallized with two independent molecules (A and B) in the asymmetric unit. The conformation of the two molecules differs slightly with the phenyl ring in molecule A, forming a dihedral angle of 15.38 (12)° with the oxime group (O—N=C), compared to the corresponding angle of 26.29 (11)° in molecule B. In the crystal, the A and B molecules are linked head-to-head by O—H⋯N hydrogen bonds, forming –A–B–A–B– zigzag chains along [010]. Within the chains and between neighbouring chains there are C—H⋯π interactions present, forming a three-dimensional structure.

The title compound, crystallized with two independent molecules A and B in the asymmetric unit (  (Table 1 and Fig. 2). Adjacent molecules of the same type are tilted against each other, with the aromatic rings (C1-C6) being inclined to one another by 77.64 (2) and 59.04 (2)° for molecules A and B, respectively. In addition, adjacent molecules of the same type exhibit weak C-H..π (C2A-H2A···Cg1 and C5B-H5B···Cg2) contacts along the b axis direction (Table 1 and Fig. 2). Along the c axis, inversion related dimers stack with an offset of 11.47 (2) Å and connected via a weak C-H..π (C9B-H9B···Cg2) contact ( Fig. 3 and Table 1).

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The OH H atoms were located in a difference Fourier map and freely refined. The C-bound H atoms were fixed geometrically (C-H = 0.95 Å) and allowed to ride on their parent atoms with U iso (H) = 1.2U eq (C).

Figure 1
A view of the molecular structure of the two independent molecules (A and B) of the title compound, with atom labelling.
Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A partial view along the a axis of the crystal packing of the title compound. The O-H···N hydrogen bonds, and the C-H···π contacts between adjacent molecules are shown as dashed lines (see Table 1).

Figure 3
A view along the b axis of three stacked molecular motifs made of A (blue) and B (green) interconnected molecules forming chains along the b axis. The hydrogen bonds and C-H···π interactions are shown as dashed lines (see Table 1).