(2E)-2-(4-Fluorobenzylidene)hydrazinecarboxamide

In the title compound, C8H8FN3O, the semicarbazide group is close to being planar, with a maximum deviation of 0.020 (1) Å, and subtends a dihedral angle of 16.63 (9)° with its attached fluorobenzene ring. In the crystal, molecules are linked by N—H⋯O hydrogen bonds, forming layers lying parallel to the bc plane.

In the title compound, C 8 H 8 FN 3 O, the semicarbazide group is close to being planar, with a maximum deviation of 0.020 (1) Å , and subtends a dihedral angle of 16.63 (9) with its attached fluorobenzene ring. In the crystal, molecules are linked by N-HÁ Á ÁO hydrogen bonds, forming layers lying parallel to the bc plane.

Comment
The semicarbazides, which are the raw material of semicarbazones, have been known to possess biological activities against many of the most common species of bacteria (Dogan et al., 1999). Semicarbazones are of much interest due to their wide spectrum of antibacterial activities (Pandeya & Dimmock, 1993). Recently some workers have reviewed the bioactivity of semicarbazones and they have exhibited anticonvulsant (Pandeya et al., 1998;Yogeeswari et al., 2004) and antitubercular (Sriram et al., 2004) properties. Accordingly and by considering the biological potential of semicarbazones, herein, we have synthesized the title compound to study its crystal structure.
The molecular structure of the title compound is shown in Fig. 1. The semicarbazone group (O1/N1-N3/C8) is essentially planar with maximum deviation of 0.020 (1) Å for atom N2. This plane makes dihedral angle of 16.63 (9)° with its terminal benzene ring (C1-C6). Bond lengths (Allen et al., 1987) and angles are within normal ranges and are comparable to related structures (Fun et al., 2009a,b).

Experimental
Semicarbazide hydrochloride (0.86 g, 7.70 mmol) and freshly recrystallized sodium acetate (0.77 g, 9.40 mmol) were dissolved in water (10 ml) following a literature procedure (Furniss et al., 1978). The reaction mixture was stirred at room temperature for 10 minutes. To this, 4-fluorobenzaldehyde (0.896 g, 7.23 mmol) was added and the mixture was shaken well. A little alcohol was added to dissolve the turbidity. The mixture was shaken for a further 10 minutes and allowed to stand. The title compound crystallizes out on standing for 6 h. The separated crystals were filtered, washed with cold water and recrystallized from ethanol to yield colourless needles. Yield: 0.98 g, 75.38%. M.p.: 506-508 K.

Refinement
Atoms H1N2, H1N3 and H2N3 were located in a difference map and refined freely [N-H = 0.90 (2), 0.87 (2) and 0.91 (2) Å respectively]. The remaining H atoms were positioned geometrically [C-H = 0.93 Å] and refined using a riding model with U iso (H) = 1.2 U eq (C). Fig. 1. The molecular structure of the title compound with atom labels with 50% probability displacement ellipsoids. 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 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.