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organic compounds
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Di-n-propyl 4,4′-dihydroxy-3,3′-{[(3aRS,7aRS)-2,3,3a,4,5,6,7,7a-octahydro-1H-benzimidazole-1,3-diyl]bis(methylene)}dibenzoate
aDepartamento de Química, Universidad Nacional de Colombia, Ciudad Universitaria, Bogotá, Colombia, and bInstitute of Physics ASCR, v.v.i., Na Slovance 2, 182 21 Praha 8, Czech Republic
*Correspondence e-mail: ariverau@unal.edu.co
The title compound, C29H38N2O6, was prepared as model for studying intramolecular hydrogen-bonding interactions. Molecules of the title compound are located on a crystallographic twofold rotation axis, which passes through the C atom linked to the two N atoms on the imidazolidine ring. The molecular structure shows the existence of two intramolecular O—H⋯N hydrogen-bonding interactions between the two N atoms of the imidazolidine moiety and the hydroxy groups in the aromatic rings. The shows the strain of ring fusion in the perhydrobenzimidazole moiety according to the endocyclic bond angles and the torsion angles, which evidence a puckering of the cyclohexane ring with respect to normal tetrahedral bond angles in an ideal chair conformation.
Related literature
For a related structure, see: Rivera et al. (2010). For crystallographic data of n-propyl 4-hydroxybenzoate, see: Zhou et al. (2010
); Feng & Grant (2006
). For background chemistry to this work, see: Lu et al. (2006
); Geise et al. (1971
). For the synthesis of the precursor, see: Murray-Rust & Riddell (1975
).
Experimental
Crystal data
|
Refinement
|
|
Data collection: CrysAlis PRO (Agilent, 2010); cell CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR2002 (Burla et al., 2003
); program(s) used to refine structure: JANA2006 (Petříček et al., 2006
); molecular graphics: DIAMOND (Brandenburg & Putz, 2005
); software used to prepare material for publication: JANA2006.
Supporting information
https://doi.org/10.1107/S1600536811036385/nk2109sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536811036385/nk2109Isup2.hkl
Supporting information file. DOI: https://doi.org/10.1107/S1600536811036385/nk2109Isup3.cml
The aminal (2R,7R,11S,16S)-1,8,10,17- tetraazapentacyclo[8.8.1.18,17.02,7.011,16]icosane (276 mg, 1.00 mmol) prepared previously following described procedures (Murray-Rust & Riddell, 1975), was dissolved in dioxane (3 ml) at 70 °C with vigorous stirring. A solution of n-propyl 4-hydroxybenzoate (360 mg, 2.00 mmol) in dioxane (3 ml) was added dropwise for about 30 min, and then water (4 ml) was added. After the addition, the reaction mixture was refluxed for about 12 h. The reaction mixture was treated with chloroform by discontinuous
(5 × 20 ml). The combined extracts were concentrated under reduced pressure until a residue appeared. The product was purified by on a silica column, and subjected to with benzene:ethyl acetate (yield 19%, m.p. = 449–450 K).Single crystals of racemic (I) were grown from a CHCl3:MeOH solution by slow evaporation of the solvent at room temperature over a period of about two weeks.All hydrogen atoms were discernible in difference Fourier maps and could be refined to reasonable geometry. According to common practice H atoms bonded to C atoms were kept in ideal positions with C–H distance 0.96 Å during the
The methyl H atoms were allowed to rotate freely about the adjacent C—C bonds. The hydroxyl H atoms were found in difference Fourier maps and their coordinates were refined freely. All H atoms were refined with thermal displacement coefficients Uiso(H) set to 1.5Ueq(C, O) for methyl and hydroxyl groups and to to 1.2Ueq(C) for the CH– and CH2- groups.Hydrogen bonding involving
has been the subject of extensive experimental and theoretical studies because hydrogen-bonding interactions of phenol itself can be regarded as a prototype to understand the attraction between the lone pair of the amine nitrogen atom and the phenolic hydroxyl proton. (Lu et al. 2006). Continuing our studies on the synthesis and structural analysis of Mannich bases derived from the title compound, (I), was obtained from n-propyl-4-hydroxybenzoate and (2R,7R,11S,16S)-1,8,10,17- tetraazapentacyclo[8.8.1.18,1702,7.011,16]icosane.The molecular structure and atom-numbering scheme for (I) are shown in Fig. 1. The six-membered ring exists in a chair conformation with a C2—C3—C4 [107.6 (1)°] bond angle which is slightly distorted respect to the normal tetrahedral bond angles in a ideal chair conformation [111.1°] (Geise, et al. 1971). These values suggest a constraint of the cyclohexane ring, which is minimized by an increasing of the C3—C4—C4i bond angle [113.4 (1)°]. The imidazolidine moiety has a half-chair conformation (C2) with intraanular bond angles ranging from 105.1 (1)° to 106.6 (1)° which are shorter respect the tetrahedrical normal bond angles, indicating that the heterocyclic ring is also strained. This conformation is adopted because the nitrogen lone pairs are oriented anti-axial to avoid electronic repulsions. The bond length and bond angle values in the propoxycarbonyl group are in a good agreement with the values observed in the
of n-propyl 4-hydroxybenzoate (Feng & Grant, 2006; Zhou, et al. 2010).Intramolecular hydrogen bonds are present between the phenolic hydroxyl groups and nitrogen atoms, the N···O distance [2.6810 (14) Å] is in a good agreement with the corresponding N···O distance in the phenol derivative [2.7096 (14) Å] (Rivera, et al. 2010).
For a related structure, see: Rivera et al. (2010). For crystallographic data of n-propyl 4-hydroxybenzoate, see: Zhou et al. (2010); Feng & Grant (2006). For background chemistry to this work, see: Lu et al. (2006); Geise et al. (1971). For the synthesis of the precursor, see: Murray-Rust & Riddell (1975).
Data collection: CrysAlis PRO (Agilent, 2010); cell
CrysAlis PRO (Agilent, 2010); data reduction: CrysAlis PRO (Agilent, 2010); program(s) used to solve structure: SIR2002 (Burla et al., 2003); program(s) used to refine structure: JANA2006 (Petříček et al., 2006); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: JANA2006 (Petříček et al., 2006).C29H38N2O6 | F(000) = 1096 |
Mr = 510.6 | Dx = 1.294 Mg m−3 |
Monoclinic, C2/c | Cu Kα radiation, λ = 1.5418 Å |
Hall symbol: -C 2yc | Cell parameters from 6637 reflections |
a = 15.8047 (4) Å | θ = 3.5–67.1° |
b = 8.7762 (3) Å | µ = 0.73 mm−1 |
c = 19.0108 (6) Å | T = 120 K |
β = 96.353 (2)° | Plate, colourless |
V = 2620.70 (14) Å3 | 0.43 × 0.18 × 0.10 mm |
Z = 4 |
Agilent Gemini A Ultra diffractometer | 2339 independent reflections |
Radiation source: Enhance Ultra (Cu) X-ray Source | 1855 reflections with I > 3σ(I) |
Mirror monochromator | Rint = 0.044 |
Detector resolution: 10.3784 pixels mm-1 | θmax = 67.2°, θmin = 4.7° |
Rotation method data acquisition using ω scans | h = −18→18 |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2010) | k = −10→9 |
Tmin = 0.638, Tmax = 1 | l = −22→22 |
18471 measured reflections |
Refinement on F2 | H atoms treated by a mixture of independent and constrained refinement |
R[F > 3σ(F)] = 0.039 | Weighting scheme based on measured s.u.'s w = 1/(σ2(I) + 0.0016I2) |
wR(F) = 0.105 | (Δ/σ)max = 0.010 |
S = 1.57 | Δρmax = 0.21 e Å−3 |
2339 reflections | Δρmin = −0.17 e Å−3 |
172 parameters | Extinction correction: B-C type 1 Lorentzian isotropic (Becker & Coppens, 1974) |
0 restraints | Extinction coefficient: 1100 (300) |
73 constraints |
C29H38N2O6 | V = 2620.70 (14) Å3 |
Mr = 510.6 | Z = 4 |
Monoclinic, C2/c | Cu Kα radiation |
a = 15.8047 (4) Å | µ = 0.73 mm−1 |
b = 8.7762 (3) Å | T = 120 K |
c = 19.0108 (6) Å | 0.43 × 0.18 × 0.10 mm |
β = 96.353 (2)° |
Agilent Gemini A Ultra diffractometer | 2339 independent reflections |
Absorption correction: multi-scan (CrysAlis PRO; Agilent, 2010) | 1855 reflections with I > 3σ(I) |
Tmin = 0.638, Tmax = 1 | Rint = 0.044 |
18471 measured reflections |
R[F > 3σ(F)] = 0.039 | 0 restraints |
wR(F) = 0.105 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.57 | Δρmax = 0.21 e Å−3 |
2339 reflections | Δρmin = −0.17 e Å−3 |
172 parameters |
Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F2 for refinement carried out on F and F2, respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement. The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program. |
x | y | z | Uiso*/Ueq | ||
O1 | 0.44235 (7) | 0.33457 (13) | 0.45643 (6) | 0.0351 (4) | |
O2 | 0.34718 (6) | 0.50352 (12) | 0.48867 (5) | 0.0273 (3) | |
O3 | 0.29215 (7) | −0.02617 (13) | 0.70432 (6) | 0.0297 (4) | |
N1 | 0.44367 (5) | −0.16285 (11) | 0.70300 (4) | 0.0242 (4) | |
C1 | 0.5 | −0.06183 (13) | 0.75 | 0.0278 (7) | |
C2 | 0.48251 (9) | −0.31564 (17) | 0.71167 (8) | 0.0242 (5) | |
C3 | 0.42460 (9) | −0.45085 (18) | 0.69460 (8) | 0.0279 (5) | |
C4 | 0.47714 (10) | −0.59581 (18) | 0.71258 (8) | 0.0293 (5) | |
C5 | 0.43457 (10) | −0.11400 (18) | 0.62864 (8) | 0.0278 (5) | |
C6 | 0.38601 (9) | 0.03362 (18) | 0.61649 (7) | 0.0246 (4) | |
C7 | 0.40693 (9) | 0.13502 (18) | 0.56533 (8) | 0.0251 (5) | |
C8 | 0.36156 (9) | 0.26911 (18) | 0.55025 (7) | 0.0245 (5) | |
C9 | 0.29302 (9) | 0.30241 (17) | 0.58796 (8) | 0.0248 (5) | |
C10 | 0.27134 (9) | 0.20348 (18) | 0.63976 (8) | 0.0262 (5) | |
C11 | 0.31679 (9) | 0.06936 (18) | 0.65395 (8) | 0.0251 (4) | |
C12 | 0.38833 (9) | 0.36954 (18) | 0.49413 (8) | 0.0257 (5) | |
C13 | 0.37042 (9) | 0.59939 (18) | 0.43146 (8) | 0.0279 (5) | |
C14 | 0.31759 (10) | 0.74213 (19) | 0.42731 (8) | 0.0327 (5) | |
C15 | 0.33797 (12) | 0.8368 (2) | 0.36391 (10) | 0.0401 (6) | |
H1a | 0.533905 | −0.000814 | 0.721944 | 0.0334* | |
H2 | 0.52318 | −0.329477 | 0.678263 | 0.029* | |
H3a | 0.40456 | −0.450366 | 0.645051 | 0.0335* | |
H3b | 0.378108 | −0.44685 | 0.723052 | 0.0335* | |
H4a | 0.440725 | −0.683417 | 0.706234 | 0.0352* | |
H4b | 0.517975 | −0.608248 | 0.679206 | 0.0352* | |
H5a | 0.406522 | −0.192525 | 0.599622 | 0.0334* | |
H5b | 0.489912 | −0.103289 | 0.612879 | 0.0334* | |
H7 | 0.454193 | 0.112066 | 0.539465 | 0.0302* | |
H9 | 0.260801 | 0.394109 | 0.577963 | 0.0297* | |
H10 | 0.224629 | 0.227666 | 0.666045 | 0.0314* | |
H13a | 0.360587 | 0.544993 | 0.387508 | 0.0335* | |
H13b | 0.429613 | 0.625746 | 0.440121 | 0.0335* | |
H14a | 0.330535 | 0.800246 | 0.46993 | 0.0392* | |
H14b | 0.258305 | 0.715585 | 0.42174 | 0.0392* | |
H15a | 0.302902 | 0.926349 | 0.36018 | 0.0602* | |
H15b | 0.396838 | 0.866083 | 0.370217 | 0.0602* | |
H15c | 0.326969 | 0.77735 | 0.321488 | 0.0602* | |
H3 | 0.3366 (14) | −0.095 (2) | 0.7126 (10) | 0.0446* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0361 (6) | 0.0382 (7) | 0.0322 (6) | 0.0103 (5) | 0.0094 (5) | 0.0056 (5) |
O2 | 0.0295 (5) | 0.0255 (6) | 0.0271 (6) | 0.0032 (4) | 0.0043 (4) | 0.0048 (4) |
O3 | 0.0301 (6) | 0.0282 (7) | 0.0311 (6) | 0.0003 (5) | 0.0038 (4) | 0.0057 (5) |
N1 | 0.0276 (6) | 0.0206 (7) | 0.0232 (7) | 0.0008 (5) | −0.0025 (5) | −0.0003 (5) |
C1 | 0.0318 (11) | 0.0226 (12) | 0.0277 (11) | 0 | −0.0024 (9) | 0 |
C2 | 0.0267 (7) | 0.0210 (8) | 0.0245 (8) | 0.0026 (6) | 0.0013 (6) | 0.0006 (6) |
C3 | 0.0300 (8) | 0.0246 (9) | 0.0278 (8) | −0.0012 (6) | −0.0029 (6) | −0.0015 (6) |
C4 | 0.0354 (8) | 0.0203 (8) | 0.0318 (9) | −0.0009 (6) | 0.0009 (7) | −0.0023 (6) |
C5 | 0.0340 (8) | 0.0259 (9) | 0.0226 (8) | 0.0050 (7) | −0.0010 (6) | −0.0002 (6) |
C6 | 0.0265 (7) | 0.0237 (8) | 0.0219 (7) | 0.0026 (6) | −0.0047 (6) | −0.0034 (6) |
C7 | 0.0261 (7) | 0.0274 (9) | 0.0213 (8) | 0.0036 (6) | −0.0002 (6) | −0.0027 (6) |
C8 | 0.0262 (7) | 0.0247 (8) | 0.0214 (7) | −0.0002 (6) | −0.0026 (6) | −0.0018 (6) |
C9 | 0.0244 (7) | 0.0219 (8) | 0.0267 (8) | 0.0025 (6) | −0.0029 (6) | −0.0033 (6) |
C10 | 0.0228 (7) | 0.0280 (9) | 0.0276 (8) | 0.0001 (6) | 0.0018 (6) | −0.0021 (6) |
C11 | 0.0265 (7) | 0.0258 (9) | 0.0219 (7) | −0.0032 (6) | −0.0021 (6) | −0.0010 (6) |
C12 | 0.0267 (7) | 0.0265 (9) | 0.0226 (8) | 0.0024 (6) | −0.0027 (6) | −0.0002 (6) |
C13 | 0.0270 (7) | 0.0306 (9) | 0.0263 (8) | −0.0012 (6) | 0.0036 (6) | 0.0071 (7) |
C14 | 0.0389 (9) | 0.0289 (9) | 0.0313 (9) | 0.0029 (7) | 0.0087 (7) | 0.0033 (7) |
C15 | 0.0486 (10) | 0.0339 (10) | 0.0400 (10) | 0.0082 (8) | 0.0147 (8) | 0.0097 (8) |
O1—C12 | 1.2134 (19) | C5—H5b | 0.96 |
O2—C12 | 1.3422 (19) | C6—C7 | 1.385 (2) |
O2—C13 | 1.4539 (19) | C6—C11 | 1.405 (2) |
O3—C11 | 1.3615 (19) | C7—C8 | 1.391 (2) |
O3—H3 | 0.93 (2) | C7—H7 | 0.96 |
N1—C1 | 1.4835 (11) | C8—C9 | 1.395 (2) |
N1—C2 | 1.4763 (17) | C8—C12 | 1.481 (2) |
N1—C5 | 1.4689 (17) | C9—C10 | 1.384 (2) |
C1—H1a | 0.96 | C9—H9 | 0.96 |
C1—H1ai | 0.96 | C10—C11 | 1.390 (2) |
C2—C2i | 1.500 (2) | C10—H10 | 0.96 |
C2—C3 | 1.512 (2) | C13—C14 | 1.503 (2) |
C2—H2 | 0.96 | C13—H13a | 0.96 |
C3—C4 | 1.537 (2) | C13—H13b | 0.96 |
C3—H3a | 0.96 | C14—C15 | 1.527 (3) |
C3—H3b | 0.96 | C14—H14a | 0.96 |
C4—C4i | 1.523 (2) | C14—H14b | 0.96 |
C4—H4a | 0.96 | C15—H15a | 0.96 |
C4—H4b | 0.96 | C15—H15b | 0.96 |
C5—C6 | 1.511 (2) | C15—H15c | 0.96 |
C5—H5a | 0.96 | ||
C12—O2—C13 | 113.86 (12) | C7—C6—C11 | 118.18 (14) |
C11—O3—H3 | 104.6 (13) | C6—C7—C8 | 122.04 (14) |
C1—N1—C2 | 105.14 (8) | C6—C7—H7 | 118.9808 |
C1—N1—C5 | 113.18 (9) | C8—C7—H7 | 118.9799 |
C2—N1—C5 | 111.58 (10) | C7—C8—C9 | 118.90 (14) |
N1—C1—N1i | 106.60 (9) | C7—C8—C12 | 118.03 (13) |
N1—C1—H1a | 109.4712 | C9—C8—C12 | 123.07 (14) |
N1—C1—H1ai | 109.4713 | C8—C9—C10 | 120.12 (14) |
N1i—C1—H1a | 109.4713 | C8—C9—H9 | 119.9408 |
N1i—C1—H1ai | 109.4712 | C10—C9—H9 | 119.9415 |
H1a—C1—H1ai | 112.196 | C9—C10—C11 | 120.42 (14) |
N1—C2—C2i | 102.26 (11) | C9—C10—H10 | 119.7917 |
N1—C2—C3 | 117.04 (11) | C11—C10—H10 | 119.7918 |
N1—C2—H2 | 109.9711 | O3—C11—C6 | 121.21 (13) |
C2i—C2—C3 | 110.96 (12) | O3—C11—C10 | 118.45 (13) |
C2i—C2—H2 | 116.1607 | C6—C11—C10 | 120.34 (14) |
C3—C2—H2 | 101.0977 | O1—C12—O2 | 122.85 (14) |
C2—C3—C4 | 107.61 (12) | O1—C12—C8 | 123.42 (14) |
C2—C3—H3a | 109.4708 | O2—C12—C8 | 113.73 (13) |
C2—C3—H3b | 109.4712 | O2—C13—C14 | 109.68 (13) |
C4—C3—H3a | 109.4711 | O2—C13—H13a | 109.4707 |
C4—C3—H3b | 109.4719 | O2—C13—H13b | 109.4714 |
H3a—C3—H3b | 111.2673 | C14—C13—H13a | 109.4706 |
C3—C4—C4i | 113.37 (13) | C14—C13—H13b | 109.4711 |
C3—C4—H4a | 109.4715 | H13a—C13—H13b | 109.2656 |
C3—C4—H4b | 109.4718 | C13—C14—C15 | 109.29 (14) |
C4i—C4—H4a | 109.4713 | C13—C14—H14a | 109.4708 |
C4i—C4—H4b | 109.4702 | C13—C14—H14b | 109.4715 |
H4a—C4—H4b | 105.271 | C15—C14—H14a | 109.4706 |
N1—C5—C6 | 113.04 (12) | C15—C14—H14b | 109.4717 |
N1—C5—H5a | 109.4711 | H14a—C14—H14b | 109.6526 |
N1—C5—H5b | 109.4709 | C14—C15—H15a | 109.4714 |
C6—C5—H5a | 109.4723 | C14—C15—H15b | 109.4714 |
C6—C5—H5b | 109.471 | C14—C15—H15c | 109.4713 |
H5a—C5—H5b | 105.6475 | H15a—C15—H15b | 109.4713 |
C5—C6—C7 | 120.11 (13) | H15a—C15—H15c | 109.4713 |
C5—C6—C11 | 121.66 (13) | H15b—C15—H15c | 109.4708 |
Symmetry code: (i) −x+1, y, −z+3/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3···N1 | 0.93 (2) | 1.82 (2) | 2.6810 (14) | 153 (2) |
Experimental details
Crystal data | |
Chemical formula | C29H38N2O6 |
Mr | 510.6 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 120 |
a, b, c (Å) | 15.8047 (4), 8.7762 (3), 19.0108 (6) |
β (°) | 96.353 (2) |
V (Å3) | 2620.70 (14) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 0.73 |
Crystal size (mm) | 0.43 × 0.18 × 0.10 |
Data collection | |
Diffractometer | Agilent Gemini A Ultra |
Absorption correction | Multi-scan (CrysAlis PRO; Agilent, 2010) |
Tmin, Tmax | 0.638, 1 |
No. of measured, independent and observed [I > 3σ(I)] reflections | 18471, 2339, 1855 |
Rint | 0.044 |
(sin θ/λ)max (Å−1) | 0.598 |
Refinement | |
R[F > 3σ(F)], wR(F), S | 0.039, 0.105, 1.57 |
No. of reflections | 2339 |
No. of parameters | 172 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.21, −0.17 |
Computer programs: CrysAlis PRO (Agilent, 2010), SIR2002 (Burla et al., 2003), JANA2006 (Petříček et al., 2006), DIAMOND (Brandenburg & Putz, 2005).
D—H···A | D—H | H···A | D···A | D—H···A |
O3—H3···N1 | 0.93 (2) | 1.82 (2) | 2.6810 (14) | 153 (2) |
Acknowledgements
We acknowledge the Dirección de Investigaciones, Sede Bogotá (DIB) de la Universidad Nacional de Colombia, for financial support of this work, as well as the Institutional research plan No. AVOZ10100521 of the Institute of Physics and the Praemium Academiae project of the Academy of Sciences of the Czech Republic. DQ acknowledges the Vicerrectoría Académica de la Universidad Nacional de Colombia for a fellowship.
References
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Hydrogen bonding involving phenols has been the subject of extensive experimental and theoretical studies because hydrogen-bonding interactions of phenol itself can be regarded as a prototype to understand the attraction between the lone pair of the amine nitrogen atom and the phenolic hydroxyl proton. (Lu et al. 2006). Continuing our studies on the synthesis and structural analysis of Mannich bases derived from phenols, the title compound, (I), was obtained from n-propyl-4-hydroxybenzoate and (2R,7R,11S,16S)-1,8,10,17- tetraazapentacyclo[8.8.1.18,1702,7.011,16]icosane.
The molecular structure and atom-numbering scheme for (I) are shown in Fig. 1. The six-membered ring exists in a chair conformation with a C2—C3—C4 [107.6 (1)°] bond angle which is slightly distorted respect to the normal tetrahedral bond angles in a ideal chair conformation [111.1°] (Geise, et al. 1971). These values suggest a constraint of the cyclohexane ring, which is minimized by an increasing of the C3—C4—C4i bond angle [113.4 (1)°]. The imidazolidine moiety has a half-chair conformation (C2) with intraanular bond angles ranging from 105.1 (1)° to 106.6 (1)° which are shorter respect the tetrahedrical normal bond angles, indicating that the heterocyclic ring is also strained. This conformation is adopted because the nitrogen lone pairs are oriented anti-axial to avoid electronic repulsions. The bond length and bond angle values in the propoxycarbonyl group are in a good agreement with the values observed in the crystal structure of n-propyl 4-hydroxybenzoate (Feng & Grant, 2006; Zhou, et al. 2010).
Intramolecular hydrogen bonds are present between the phenolic hydroxyl groups and nitrogen atoms, the N···O distance [2.6810 (14) Å] is in a good agreement with the corresponding N···O distance in the phenol derivative [2.7096 (14) Å] (Rivera, et al. 2010).