Isopropyl 4-aminobenzoate

The title compound crystallizes with two molecules in the asymmetric unit, which form double chains in the crystal linked by N—H⋯O and N—H⋯N hydrogen bonds.

The present paper reports the synthesis and crystal structure of the title compound, (I). Compound I crystallizes with two molecules in the asymmetric unit (Fig. 1). There are slight differences in the conformations of each molecule: for A, the dihedral angle between the planes of the phenyl ring and its i-propyl substituent is 65.4 (3) while for B data reports this angle is 67.8 (3) . For both molecules, the H atoms of the amino substituents are not coplanar with their attached phenyl ring. This is indicated by the dihedral angles between this group and its phenyl ring [11.5 (3) and 24.2 (5) for A and B, respectively] and the sum of the angles subtended at the N (358 and 352 for A and B, respectively), which shows that N2 is slightly more pyramidal than N1. These differences in the conformations of A and B are most clearly shown in an overlay of both molecules centered on the phenyl ring of both (Fig. 2).

Synthesis and crystallization
4-Aminobenzoic acid (1.0 g), purchased from Sigma-Aldrich, was taken in a 100 ml round-bottomed flask. Then, 20 ml of 2-propanol and a catalytic amount of conc. H 2 SO 4 was added and the reaction mixture was refluxed for 4 h. The reaction was confirmed to be complete using thin-layer chromatography and the mixture was then quenched with water, the precipitate formed was collected by filtration and dried. Pink needles suitable for single-crystal X-ray diffraction were grown by slow evaporation, at room temperature of a solution in ethyl acetate. Yield (79%), m. p. 355-357 K. The reaction scheme is shown in Fig. 4.

Refinement
Crystal data, data collection and structure refinement details for I are summarized in Table 2.

Figure 3
Partial packing diagram for I showing the formation of [100] double chains linked by N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds (shown as dashed lines).

Figure 1
The molecular structure of I with displacement ellipsoids drawn at the 30% probability level.    Reaction scheme. where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.11 e Å −3 Δρ min = −0.14 e Å −3 Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

data-2
IUCrData (2022). 7, x220904 Refinement. All hydrogen atoms were placed geometrically and refined as riding atoms with their U iso values 1.2 times (1.5 times for CH 3 ) that of their attached atoms.