(4-Nitrophenyl)methanol

In the crystal of the title compound, C7H7NO3, molecules associate into infinite chains via O—H⋯O(NO2) hydrogen bonds propagating in the [101] direction. These chains are linked via C—H⋯O(NO2) hydrogen bonds to form double-stranded ribbons lying parallel to the ac plane. The ribbons stack along the b axis by means of π–π interactions involving the benzene rings and the nitro group. The centroid–centroid distances of the alternating parallel aromatic rings are 3.6514 (7) and 3.8044 (7) Å.

In the crystal of the title compound, C 7 H 7 NO 3 , molecules associate into infinite chains via O-HÁ Á ÁO(NO 2 ) hydrogen bonds propagating in the [101] direction. These chains are linked via C-HÁ Á ÁO(NO 2 ) hydrogen bonds to form doublestranded ribbons lying parallel to the ac plane. The ribbons stack along the b axis by means ofinteractions involving the benzene rings and the nitro group. The centroid-centroid distances of the alternating parallel aromatic rings are 3.6514 (7) and 3.8044 (7) Å .

Related literature
For the crystal structure of a Zn II complex with O-coordinated 4-nitrobenzyl alcohol, see: Koller et al. (2009). For a survey of typical bond lengths in organic compounds, see: Allen et al. (2006).

Comment
The title compound, (4-nitrophenyl)methanol [common name: 4-nitrobenzyl alcohol], is a readily available reactive organic building block, commonly used in many organic reactions. As it can separate from the reaction mixture in the form of thin crystals and thus be mistakenly taken for the desired product (D. Drahoňovský, private communication), we decided to determined its molecular structure which surprisingly was unknown. The only structurally characterized compound comprising the title alcohol reported to date is a Zn(II) complex, [ZnL 2 (4-O 2 NC 6 H 4 CH 2 OH) 2 (H 2 O) 2 ](NTf 2 ) 2 [where L = 1-(trifluoromethyl)-1,2-benziodoxol-3(1H)-one and Tf = CF 3 SO 3 ], isolated from the reaction mixture after zinc-catalysed trifluoromethylation of alcohols with L and Zn(NTf 2 ) 2 (Koller et al., 2009).
The molecular geometry of the title compound, Fig. 1, is rather unexceptional with bond distances falling in the usual ranges (Allen et al., 2006). The substituents in the para positions of the benzene ring bind symmetrically as indicated by the O2/O3-N1-C4 angles of 118.10 (9) ° and 119.34 (9) ° for the NO 2 group and by the angles C2/C6-C1-C7 of 119.21 (10) ° and 121.32 (10) ° for the CH 2 OH moiety. The nitro group is rotated from the plane of the benzene ring by as little as 0.44 (13) °. On the other hand, the hydroxy group is displaced from the plane of the central ring, being rotated by the pivotal C1-C7 bond. The perpendicular distance of O1 atom from the plane of the benzene ring is 0.356 (1) Å and the torsion angle C6-C1-C7-O1 is 16.73 (16) °. A relatively small but statistically significant difference observed for the individual N-O distances [viz: N1-O2 = 1.2369 (12) Å and N1-O3 = 1.2240 (13) Å] can be accounted for by different intermolecular interactions in which the respective NO 2 oxygen atoms participate.
In the crystal, molecules associate into ribbons via a combination of O-H···O and C-H···O hydrogen bonds ( Fig. 2 and Table 1). The shorter O1-H1O···O2 interactions result in the formation of infinite chains from molecules related by translation in the [1 0 1] direction, whereas the soft C3-H3···O3 contacts are formed between inversion-related molecules and thus cross-link the chains with their parallel, inversion-related counterparts into infinite ribbons oriented parallel to the ac plane.
Furthermore, the molecules associate into columnar stacks oriented along the crystallographic b-axis by means of π···π interactions (Figs. 3 and 4). The interacting molecules lie across crystallographic inversion centers and are therefore exactly parallel. Mutual offset of the interacting molecules by ca. 1.4 Å (pairs A in Fig. 3) and 1.7 Å (pairs B in Fig. 3) allows for efficient interactions between the the π-systems of the benzene rings and also for interactions between the πsystems of the benzene rings and the nitro groups. Distances of the centroids of the benzene rings are 3.6514 (7) Å for molecules located around inversion centres at b/2 (pairs A) and 3.8044 (7) Å for molecules related by the inversion centres at b = 0 and 1 (pairs B

Experimental
Yellowish prismatic crystals suitable for X-ray diffraction analysis were selected directly from a commercial sample of the title compound (Aldrich, 99%). Attempts to recrystallize the compound from hot heptane led only to very thin, platelike crystal aggregates, which were not suitable for -ray diffraction analysis.

Refinement
The OH hydrogen atom was located in a difference electron density map and refined freely. The C-bound H atoms were included in calculated positions and refined as riding atoms: C-H = 0.95 and 0.97 Å for aromatic and methylene H atoms, respectively, with U iso (H) =1.2U eq (C).

Figure 1
A view of the molecular structure of the title compound, showing the atom-labeling scheme. The displacement ellipsoids are drawn at the 50% probability level.   A view along the a axis of the crystal packing of the title compound, highlighting the interplay of hydrogen bonding (see Table 1) and π···π interactions [The yellow box limits the section presented in Fig. 3].

(4-nitrophenyl)methanol
Crystal data C 7 H 7 NO 3 M r = 153.14 Triclinic, P1 Hall symbol: -P 1 a = 6.2216 (5)  Refinement. Refinement of F 2 against all diffractions. 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.