The structures of 1-methyl-3-nitropyrazole and 1-methyl-4-nitropyrazole, C
4H
5N
3O
2, have been determined. The 3-nitro derivative has crystallographic
m-symmetry while the 4-nitro compound has no imposed symmetry. The significant differences in bond distances and angles between the structures are ascribable to the electron-withdrawing effects of the nitro group attached to C3 or C4, respectively. In both structures, the molecules are organized into layers by an extensive network of C—H
O or C—H
N hydrogen interactions. Within a layer, the molecules are arranged in a similar way, although differences of up to 0.3 Å in the analogous H
O or H
N intermolecular distances are observed. The cohesion of the layers is due to van der Waals and C—H
O contacts.
Supporting information
CCDC references: 142761; 142762
Compounds (I) and (II) were prepared according to Luitjen & van Thuijl (1979). Crystals of (I) and (II) were obtained by recrystallization from EtOAc.
In (I), the structure was solved in the centrosymmetric space group since the intensity statistics indicate the space group Pnam. As the molecules are placed on mirror planes and the nitro groups are slightly twisted in these kind of compounds (CSD; Allen et al. 1991, version of April 1999), refinements in the Pna21 space group, also compatible with the systematic absences, were also carried out. The structure can be better described in the centrosymmetric space group since the refinement proceeded well in this group, i.e. similar geometrical parameters and slightly lower isotropic displacement parameters for atom O9.
Data collection: Philips PW1100 (Hornstra & Vossers, 1973) for (I); CRYSOM (Seifert, 1996) for (II). For both compounds, cell refinement: LSUCRE (Appleman, 1984). Data reduction: Xtal3.2 (Hall et al., 1992) for (I); Xtal3.2 for (II). For both compounds, program(s) used to solve structure: Xtal3.2?; program(s) used to refine structure: Xtal3.2; molecular graphics: Xtal3.2; software used to prepare material for publication: Xtal3.2.
(I) 1-methyl-3-nitro-pyrazole
top
Crystal data top
C4H5N3O2 | F(000) = 264 |
Mr = 127.1 | Dx = 1.471 Mg m−3 |
Orthorhombic, Pnam | Cu Kα radiation, λ = 1.54178 Å |
Hall symbol: -P 2c -2n | Cell parameters from 69 reflections |
a = 10.5062 (5) Å | θ = 2–45° |
b = 8.5940 (4) Å | µ = 1.04 mm−1 |
c = 6.3562 (3) Å | T = 293 K |
V = 573.90 (5) Å3 | Rectangular prism, colourless |
Z = 4 | 0.60 × 0.50 × 0.23 mm |
Data collection top
Philips PW1100 four-circle diffractometer | 571 reflections with I > 0 |
Radiation source: X-ray tube | Rint = 0.044 |
Graphite monochromator | θmax = 67.5°, θmin = 6.7° |
ω/2θ scans | h = 0→12 |
Absorption correction: ψ-scan (North et al., 1968) | k = −10→10 |
Tmin = 0.518, Tmax = 0.788 | l = 0→7 |
1164 measured reflections | 2 standard reflections every 90 min |
571 independent reflections | intensity decay: none |
Refinement top
Refinement on F | 0 constraints |
Least-squares matrix: full | H-atom parameters not refined |
R[F2 > 2σ(F2)] = 0.043 | w = k/[(A + B Fo)2(C + D(sinθ)/λ)] |
wR(F2) = 0.045 | (Δ/σ)max < 0.001 |
S = 1.02 | Δρmax = 0.22 e Å−3 |
571 reflections | Δρmin = −0.19 e Å−3 |
56 parameters | Extinction correction: (Zachariasen, 1967), Eq22 p292 Cryst. Comp. Munksgaard 1970 |
0 restraints | Extinction coefficient: 16 (6) |
Crystal data top
C4H5N3O2 | V = 573.90 (5) Å3 |
Mr = 127.1 | Z = 4 |
Orthorhombic, Pnam | Cu Kα radiation |
a = 10.5062 (5) Å | µ = 1.04 mm−1 |
b = 8.5940 (4) Å | T = 293 K |
c = 6.3562 (3) Å | 0.60 × 0.50 × 0.23 mm |
Data collection top
Philips PW1100 four-circle diffractometer | 571 reflections with I > 0 |
Absorption correction: ψ-scan (North et al., 1968) | Rint = 0.044 |
Tmin = 0.518, Tmax = 0.788 | 2 standard reflections every 90 min |
1164 measured reflections | intensity decay: none |
571 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.043 | 0 restraints |
wR(F2) = 0.045 | H-atom parameters not refined |
S = 1.02 | Δρmax = 0.22 e Å−3 |
571 reflections | Δρmin = −0.19 e Å−3 |
56 parameters | |
Special details top
Experimental. Both structures were solved by direct methods (SIR97; Altomare et al., 1997). The H-atom positions were located on the corresponding difference Fourier synthesis and were kept fixed during refinement. In both compounds, and due to the geometry of the intermolecular contacts in which the C6 methyl group was involved (Tables 2 and 4), new difference Fourier maps were computed in the last steps of refinement in order to confirm these H-atom positions. The methyl group in (I) and (II) adopts the same conformation, although slightly distorted in (II), (Tables 1 and 3) and no indication of disorder was found. In (II), the P21/c space group was chosen instead of P21/n because the β angle is smaller in the former (7.420, 10.180 and 8.749 Å, and 118.44°). In both compounds, the criterion for the observed reflections was selected in order to perform the refinement with more than ten reflections per parameter. Due to the rather bad quality of the crystals in (II), the achieved precision using all reflections as observed was not good, so the unusual value of 0.75 was chosen and new refinements were carried out. The weighting schemes were established in an empirical way so as to give no trends in <wΔ2F> versus <Fo> or <sinθ/λ>: w = K/[(A + BFo)2][C + Dsinθ/λ]. The parameters A, B, C and D were adjusted to flatten the initial trends (PESOS; Martínez-Ripoll & Cano, 1975). |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
N1 | 0.13497 (16) | 0.2825 (2) | 1/4 | 0.0246 (9) | |
N2 | 0.03272 (16) | 0.3748 (2) | 1/4 | 0.0198 (8) | |
C3 | 0.0822 (2) | 0.5158 (2) | 1/4 | 0.0213 (10) | |
C4 | 0.2139 (2) | 0.5173 (3) | 1/4 | 0.0375 (13) | |
C5 | 0.2443 (2) | 0.3637 (3) | 1/4 | 0.0379 (13) | |
C6 | 0.1188 (3) | 0.1150 (3) | 1/4 | 0.0410 (14) | |
N7 | −0.0017 (2) | 0.6490 (2) | 1/4 | 0.0300 (10) | |
O8 | −0.11584 (17) | 0.6290 (2) | 1/4 | 0.0407 (10) | |
O9 | 0.0478 (3) | 0.7769 (2) | 1/4 | 0.0634 (14) | |
H4 | 0.27059 | 0.60650 | 1/4 | 0.05900* | |
H5 | 0.32337 | 0.31664 | 1/4 | 0.05600* | |
H61 | 0.20302 | 0.06790 | 1/4 | 0.05900* | |
H62 | 0.07152 | 0.08229 | 0.12590 | 0.05900* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0228 (9) | 0.0302 (10) | 0.0208 (9) | 0.0055 (7) | 0 | 0 |
N2 | 0.0166 (8) | 0.0255 (9) | 0.0173 (8) | 0.0006 (7) | 0 | 0 |
C3 | 0.0257 (10) | 0.0252 (10) | 0.0132 (9) | −0.0037 (8) | 0 | 0 |
C4 | 0.0291 (12) | 0.0461 (14) | 0.0374 (13) | −0.0145 (11) | 0 | 0 |
C5 | 0.0173 (10) | 0.0569 (16) | 0.0395 (13) | 0.0031 (10) | 0 | 0 |
C6 | 0.0478 (15) | 0.0274 (12) | 0.0478 (15) | 0.0118 (11) | 0 | 0 |
N7 | 0.0450 (12) | 0.0246 (10) | 0.0203 (9) | −0.0003 (8) | 0 | 0 |
O8 | 0.0369 (10) | 0.0411 (10) | 0.0441 (11) | 0.0141 (8) | 0 | 0 |
O9 | 0.0824 (16) | 0.0235 (9) | 0.0843 (16) | −0.0093 (10) | 0 | 0 |
Geometric parameters (Å, º) top
N1—N2 | 1.335 (2) | C4—C5 | 1.358 (4) |
N1—C5 | 1.344 (3) | C5—H5 | 0.924 (2) |
N1—C6 | 1.450 (3) | C6—H61 | 0.973 (3) |
N2—C3 | 1.319 (3) | C6—H62i | 0.9734 (16) |
C3—C4 | 1.383 (3) | C6—H62 | 0.9734 (16) |
C3—N7 | 1.445 (3) | N7—O8 | 1.212 (3) |
C4—H4 | 0.971 (3) | N7—O9 | 1.216 (3) |
| | | |
H62···H62i | 1.5776 (1) | C4···O8 | 3.527 (3) |
H61···H62i | 1.5957 (1) | N2···C3 | 3.5275 (12) |
H61···H62 | 1.5957 (1) | N2···C3 | 3.5275 (12) |
N1···H61 | 1.9781 (18) | N2···O9 | 3.5377 (12) |
N1···H5 | 2.0010 (17) | N2···O9 | 3.5377 (12) |
N1···H62i | 2.0069 (17) | C6···H62ii | 3.547 (2) |
N1···H62 | 2.0069 (17) | C6···H62vii | 3.547 (2) |
C4···H5 | 2.073 (3) | C5···H62iii | 3.558 (2) |
N1···C3 | 2.080 (3) | C5···H62iv | 3.558 (2) |
C5···H4 | 2.105 (3) | C5···N7 | 3.562 (3) |
C3···H4 | 2.127 (2) | C4···O8 | 3.5698 (14) |
O8···O9 | 2.138 (3) | C4···O8 | 3.5698 (14) |
C3···C5 | 2.146 (3) | C3···N7 | 3.5808 (13) |
N1···C4 | 2.182 (3) | C3···N7 | 3.5808 (13) |
N2···C5 | 2.225 (3) | C4···O8 | 3.595 (3) |
N2···C4 | 2.264 (3) | C4···C6 | 3.599 (4) |
C3···O9 | 2.273 (3) | C5···H62vi | 3.603 (2) |
C3···O8 | 2.297 (3) | C5···H62v | 3.603 (2) |
N2···N7 | 2.384 (3) | N7···H61 | 3.619 (2) |
N2···C6 | 2.409 (3) | O8···O9 | 3.625 (3) |
H5···H61 | 2.4836 (1) | C3···C3 | 3.6276 (14) |
C5···C6 | 2.512 (4) | C3···C3 | 3.6276 (14) |
C4···N7 | 2.532 (3) | N1···H4 | 3.6569 (9) |
O8···H61 | 2.5468 (18) | N1···H4 | 3.6569 (9) |
H4···H5 | 2.5520 (1) | N2···C5 | 3.659 (3) |
O8···H4 | 2.5670 (18) | C5···H61v | 3.6724 (14) |
C5···H61 | 2.579 (3) | C5···H61 | 3.6724 (14) |
H62···H62ii | 2.6116 (1) | C4···C6v | 3.728 (2) |
N2···H62 | 2.6659 (16) | C4···C6 | 3.728 (2) |
N2···H62i | 2.6659 (16) | C6···O9 | 3.745 (2) |
N2···O8 | 2.685 (2) | C6···O9 | 3.745 (2) |
N2···H5 | 2.7466 (17) | N1···O9 | 3.7481 (16) |
O9···H62 | 2.7519 (18) | N1···O9 | 3.7481 (16) |
O9···H62 | 2.7519 (18) | C3···H62i | 3.810 (2) |
O9···H4 | 2.761 (2) | C3···H62 | 3.810 (2) |
C6···H5 | 2.761 (3) | O8···H62 | 3.8353 (18) |
C4···O9 | 2.832 (3) | O8···H62 | 3.8353 (18) |
H5···H62iii | 2.8590 (1) | C4···H61 | 3.864 (3) |
H5···H62iv | 2.8590 (1) | C6···O8 | 3.8655 (17) |
N7···H4 | 2.884 (2) | C6···O8 | 3.8655 (17) |
H4···H62v | 2.9161 (1) | C5···H4 | 3.8744 (16) |
H4···H62vi | 2.9161 (1) | C5···H4 | 3.8744 (16) |
O9···H62 | 2.9571 (13) | O8···H5 | 3.8823 (10) |
O9···H62 | 2.9571 (13) | O8···H5 | 3.8823 (10) |
O9···H61 | 2.986 (2) | O8···H5 | 3.8830 (18) |
C6···O9 | 3.000 (3) | N7···H62 | 3.8831 (18) |
C3···H5 | 3.057 (2) | N7···H62 | 3.8831 (18) |
O9···H4 | 3.080 (3) | N2···N2 | 3.8994 (14) |
N2···H5 | 3.0942 (17) | N2···N2 | 3.8994 (14) |
C5···H62i | 3.125 (3) | C3···H61 | 3.9232 (12) |
C5···H62 | 3.125 (3) | C3···H61v | 3.9232 (12) |
N1···H4 | 3.1277 (18) | C5···O9 | 3.928 (2) |
C6···H5 | 3.159 (3) | C5···O9 | 3.928 (2) |
N7···H4 | 3.184 (2) | C4···O9 | 3.929 (3) |
N2···H61 | 3.1870 (17) | C4···H62iii | 3.933 (2) |
N2···H4 | 3.1955 (17) | C4···H62iv | 3.933 (2) |
N2···N7 | 3.2013 (4) | C5···C6iii | 3.939 (4) |
N2···N7 | 3.2013 (4) | C3···H5 | 3.944 (2) |
H4···H61v | 3.2074 (2) | N7···H5 | 3.9604 (12) |
H4···H61 | 3.2074 (2) | N7···H5v | 3.9604 (12) |
N1···O8 | 3.2739 (6) | C6···N7 | 3.966 (2) |
N1···O8 | 3.2739 (6) | C6···N7 | 3.966 (2) |
N2···O8 | 3.2961 (7) | N1···O8 | 3.976 (3) |
N2···O8 | 3.2961 (7) | C5···N7 | 4.075 (2) |
C4···H61 | 3.3243 (7) | C5···N7 | 4.075 (2) |
C4···H61v | 3.3243 (7) | N7···N7 | 4.0819 (17) |
C4···H62v | 3.3321 (17) | N7···N7 | 4.0819 (17) |
C4···H62vi | 3.3321 (17) | C5···C6 | 4.103 (2) |
N1···H5 | 3.3828 (17) | C5···C6v | 4.103 (2) |
C6···H4 | 3.3848 (10) | C5···O9 | 4.107 (3) |
C6···H4 | 3.3848 (10) | C4···N7 | 4.137 (2) |
N7···H62 | 3.4028 (13) | C4···N7 | 4.137 (2) |
N7···H62 | 3.4028 (13) | C4···N7 | 4.142 (3) |
H5···H62 | 3.4176 (1) | N7···O8 | 4.1635 (17) |
H5···H62i | 3.4176 (1) | N7···O8 | 4.1635 (17) |
C3···O8 | 3.4313 (10) | C6···N7 | 4.200 (3) |
C3···O8 | 3.4313 (10) | N2···C4 | 4.204 (2) |
C5···O8 | 3.4533 (11) | N2···C4 | 4.204 (2) |
C5···O8 | 3.4533 (11) | N1···C4 | 4.221 (2) |
N2···O9 | 3.459 (2) | N1···C4 | 4.221 (2) |
N1···N7 | 3.462 (3) | C3···O9 | 4.277 (2) |
C3···C6 | 3.466 (3) | C3···O9 | 4.277 (2) |
O9···H5v | 3.4712 (10) | N1···C3 | 4.2793 (18) |
O9···H5 | 3.4712 (10) | N1···C3 | 4.2793 (18) |
O8···H62 | 3.4757 (13) | N1···C5 | 4.293 (3) |
O8···H62 | 3.4757 (13) | N1···O9 | 4.346 (3) |
H5···H62v | 3.4843 (1) | N2···C6 | 4.350 (3) |
H5···H62vi | 3.4843 (1) | C4···C5v | 4.377 (3) |
C6···O8iii | 3.489 (3) | C4···C5 | 4.377 (3) |
N2···H61 | 3.4988 (17) | C3···O8 | 4.402 (3) |
N1···N7 | 3.5224 (12) | C4···C6iii | 4.403 (4) |
N1···N7 | 3.5224 (12) | | |
| | | |
N2—N1—C5 | 112.3 (2) | H5—C5—C4 | 129.5 (3) |
N2—N1—C6 | 119.7 (2) | N1—C5—C4 | 107.7 (2) |
C5—N1—C6 | 128.0 (2) | H61—C6—H62i | 110.12 (17) |
C3—N2—N1 | 103.2 (2) | H61—C6—H62 | 110.12 (17) |
N2—C3—C4 | 113.8 (2) | H61—C6—N1 | 107.8 (2) |
N2—C3—N7 | 119.2 (2) | H62i—C6—H62 | 108.3 (3) |
C4—C3—N7 | 127.1 (2) | H62i—C6—N1 | 110.26 (16) |
H4—C4—C5 | 128.6 (2) | H62—C6—N1 | 110.26 (16) |
H4—C4—C3 | 128.4 (3) | O8—N7—O9 | 123.5 (2) |
C5—C4—C3 | 103.0 (2) | O8—N7—C3 | 119.5 (2) |
H5—C5—N1 | 122.8 (3) | O9—N7—C3 | 117.1 (2) |
| | | |
C5—N1—N2—C3 | −0.0001 | N1—N2—C3—N7 | 180.0000 |
C6—N1—N2—C3 | 180.0000 | N2—C3—C4—C5 | −0.0001 |
N2—N1—C5—C4 | −0.0001 | N2—C3—C4—H4 | 180.0000 |
N2—N1—C5—H5 | 180.0000 | N7—C3—C4—C5 | 180.0000 |
C6—N1—C5—C4 | 180.0000 | N7—C3—C4—H4 | −0.0001 |
C6—N1—C5—H5 | −0.0001 | N2—C3—N7—O8 | 0.0 (2) |
N2—N1—C6—H61 | 180 | N2—C3—N7—O9 | 180.0000 |
N2—N1—C6—H62 | 60 | C4—C3—N7—O8 | 180.0000 |
N2—N1—C6—H62i | −60 | C4—C3—N7—O9 | −0.0001 |
C5—N1—C6—H61 | 0.0001 | C3—C4—C5—N1 | −0.0001 |
C5—N1—C6—H62 | −120.26 (19) | C3—C4—C5—H5 | 180.0000 |
C5—N1—C6—H62i | 120.26 (19) | H4—C4—C5—N1 | 180.0000 |
N1—N2—C3—C4 | −0.0001 | H4—C4—C5—H5 | −0.0001 |
Symmetry codes: (i) x, y, −z+1/2; (ii) −x, −y, −z; (iii) x+1/2, −y+1/2, −z+1/2; (iv) x+1/2, −y+1/2, z; (v) −x+1/2, y+1/2, −z; (vi) −x+1/2, y+1/2, z+1/2; (vii) −x, −y, z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C4—H4···O8viii | 0.97 | 2.57 | 3.527 (3) | 170 |
C6—H61···O8iii | 0.97 | 2.55 | 3.489 (3) | 163 |
C5—H5···N2iii | 0.92 | 2.75 | 3.659 (3) | 169 |
C6—H62···O9ix | 0.97 | 2.75 | 3.000 (3) | 95 |
Symmetry codes: (iii) x+1/2, −y+1/2, −z+1/2; (viii) x+1/2, −y+3/2, −z+1/2; (ix) x, y−1, z. |
(II) 1-methyl-4-nitropyrazole
top
Crystal data top
C4H5N3O2 | F(000) = 264 |
Mr = 127.1 | Dx = 1.453 Mg m−3 |
Monoclinic, P21/c | Cu Kα radiation, λ = 1.54178 Å |
Hall symbol: -P 2ybc | Cell parameters from 49 reflections |
a = 7.4197 (8) Å | θ = 2–45° |
b = 10.1803 (15) Å | µ = 1.03 mm−1 |
c = 8.3529 (10) Å | T = 293 K |
β = 112.924 (8)° | Rhombohedral prism, colourless |
V = 581.11 (13) Å3 | 0.50 × 0.33 × 0.23 mm |
Z = 4 | |
Data collection top
Philips PW1100 four-circle four-circle diffractometer | 854 reflections with I > 0.75σ(I) |
Radiation source: X-ray tube | Rint = 0.059 |
Graphite monochromator | θmax = 67.5°, θmin = 6.5° |
ω/2θ scans | h = −8→8 |
Absorption correction: ψ-scan (North et al., 1968) | k = 0→12 |
Tmin = 0.569, Tmax = 0.790 | l = 0→9 |
1181 measured reflections | 2 standard reflections every 90 min |
1011 independent reflections | intensity decay: 5.8% |
Refinement top
Refinement on F | 0 constraints |
Least-squares matrix: full | H-atom parameters not refined |
R[F2 > 2σ(F2)] = 0.071 | w = k/[(A + B Fo)2(C + D(sinθ)/λ)] |
wR(F2) = 0.08 | (Δ/σ)max < 0.001 |
S = 1.00 | Δρmax = 0.32 e Å−3 |
854 reflections | Δρmin = −0.32 e Å−3 |
83 parameters | Extinction correction: (Zachariasen, 1967), Eq22 p292 Cryst. Comp. Munksgaard 1970 |
0 restraints | Extinction coefficient: 154 (22) |
Crystal data top
C4H5N3O2 | V = 581.11 (13) Å3 |
Mr = 127.1 | Z = 4 |
Monoclinic, P21/c | Cu Kα radiation |
a = 7.4197 (8) Å | µ = 1.03 mm−1 |
b = 10.1803 (15) Å | T = 293 K |
c = 8.3529 (10) Å | 0.50 × 0.33 × 0.23 mm |
β = 112.924 (8)° | |
Data collection top
Philips PW1100 four-circle four-circle diffractometer | 854 reflections with I > 0.75σ(I) |
Absorption correction: ψ-scan (North et al., 1968) | Rint = 0.059 |
Tmin = 0.569, Tmax = 0.790 | 2 standard reflections every 90 min |
1181 measured reflections | intensity decay: 5.8% |
1011 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.071 | 0 restraints |
wR(F2) = 0.08 | H-atom parameters not refined |
S = 1.00 | Δρmax = 0.32 e Å−3 |
854 reflections | Δρmin = −0.32 e Å−3 |
83 parameters | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
N1 | 0.0312 (4) | 0.1918 (2) | 0.2703 (3) | 0.0299 (12) | |
N2 | 0.1210 (4) | 0.3077 (3) | 0.3355 (4) | 0.0396 (13) | |
C3 | 0.2692 (5) | 0.2764 (3) | 0.4797 (4) | 0.0375 (15) | |
C4 | 0.2744 (4) | 0.1406 (3) | 0.5061 (4) | 0.0297 (14) | |
C5 | 0.1188 (4) | 0.0904 (3) | 0.3691 (4) | 0.0315 (13) | |
C6 | −0.1426 (5) | 0.1892 (4) | 0.1099 (5) | 0.0456 (17) | |
N7 | 0.4085 (4) | 0.0687 (3) | 0.6467 (4) | 0.0394 (14) | |
O8 | 0.3809 (5) | −0.0502 (3) | 0.6533 (4) | 0.0657 (16) | |
O9 | 0.5457 (4) | 0.1257 (3) | 0.7540 (4) | 0.0637 (15) | |
H3 | 0.35881 | 0.34098 | 0.54659 | 0.03569* | |
H5 | 0.06444 | 0.00695 | 0.33653 | 0.02966* | |
H61 | −0.25020 | 1/4 | 0.10470 | 0.04274* | |
H62 | −0.18370 | 0.10000 | 0.06210 | 0.04274* | |
H63 | −0.11100 | 0.24490 | 0.02650 | 0.04274* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0327 (13) | 0.0331 (14) | 0.0278 (13) | −0.0030 (10) | 0.0159 (11) | 0.0018 (10) |
N2 | 0.0430 (16) | 0.0300 (14) | 0.0468 (17) | −0.0017 (11) | 0.0186 (13) | 0.0053 (11) |
C3 | 0.0397 (17) | 0.0321 (18) | 0.0416 (19) | −0.0080 (13) | 0.0169 (16) | −0.0048 (13) |
C4 | 0.0312 (15) | 0.0347 (17) | 0.0276 (16) | 0.0004 (12) | 0.0161 (12) | 0.0015 (12) |
C5 | 0.0356 (16) | 0.0271 (15) | 0.0354 (16) | −0.0005 (12) | 0.0177 (13) | −0.0036 (12) |
C6 | 0.0389 (18) | 0.055 (2) | 0.0373 (19) | −0.0009 (15) | 0.0091 (15) | 0.0071 (16) |
N7 | 0.0379 (15) | 0.0444 (18) | 0.0360 (15) | 0.0032 (12) | 0.0146 (12) | 0.0015 (12) |
O8 | 0.073 (2) | 0.0434 (16) | 0.0652 (19) | 0.0076 (14) | 0.0100 (15) | 0.0174 (13) |
O9 | 0.0491 (16) | 0.076 (2) | 0.0468 (15) | −0.0065 (14) | −0.0021 (13) | −0.0003 (14) |
Geometric parameters (Å, º) top
N1—C5 | 1.323 (4) | C4—N7 | 1.412 (4) |
N1—N2 | 1.360 (4) | C5—H5 | 0.935 (3) |
N1—C6 | 1.453 (4) | C6—H62 | 0.991 (4) |
N2—C3 | 1.315 (4) | C6—H63 | 0.994 (4) |
C3—H3 | 0.947 (3) | C6—H61 | 0.998 (4) |
C3—C4 | 1.397 (4) | N7—O9 | 1.211 (4) |
C4—C5 | 1.369 (4) | N7—O8 | 1.232 (4) |
| | | |
H61···H63 | 1.4218 (1) | C6···O9 | 3.538 (5) |
H62···H63 | 1.6372 (2) | N2···O9 | 3.539 (5) |
H61···H62 | 1.6849 (2) | C6···H3 | 3.541 (4) |
N1···H5 | 1.950 (2) | C5···O9 | 3.545 (3) |
N1···H63 | 1.969 (2) | N2···C6ii | 3.546 (6) |
N2···H3 | 1.978 (2) | C4···C6 | 3.577 (4) |
N1···H62 | 2.068 (2) | C5···H61 | 3.584 (3) |
N1···H61 | 2.091 (2) | C4···H5 | 3.589 (3) |
C4···H3 | 2.122 (3) | C3···O8 | 3.592 (4) |
N1···C3 | 2.125 (4) | N2···N7 | 3.592 (4) |
C4···H5 | 2.137 (3) | N2···H62ii | 3.593 (4) |
O8···O9 | 2.147 (4) | N1···H3 | 3.613 (3) |
N1···C4 | 2.154 (3) | C3···O8 | 3.614 (4) |
C3···C5 | 2.209 (4) | N7···H3ii | 3.619 (3) |
N2···C4 | 2.226 (4) | N7···H62 | 3.622 (2) |
N2···C5 | 2.230 (4) | C5···H63 | 3.630 (3) |
C4···O9 | 2.262 (3) | C3···C6ii | 3.637 (6) |
C4···O8 | 2.269 (4) | N7···H5 | 3.648 (3) |
N2···C6 | 2.441 (4) | N2···C3 | 3.650 (5) |
C5···N7 | 2.482 (3) | N1···O8 | 3.654 (5) |
C5···C6 | 2.488 (4) | C5···O8 | 3.662 (5) |
H5···H62 | 2.5008 (2) | C3···H5i | 3.677 (3) |
C3···N7 | 2.522 (4) | C3···N7 | 3.679 (5) |
N2···H5i | 2.556 (3) | O8···O9 | 3.729 (5) |
N2···H63 | 2.564 (3) | N1···C6ii | 3.745 (5) |
O9···H62 | 2.588 (2) | C4···N7 | 3.748 (5) |
O9···H61 | 2.631 (3) | C3···H63 | 3.751 (3) |
C6···H5 | 2.668 (3) | C5···O9 | 3.753 (5) |
C5···H62 | 2.672 (3) | N1···C4 | 3.760 (5) |
O8···H3 | 2.734 (3) | O8···O8 | 3.775 (5) |
N2···H61 | 2.741 (3) | C5···C5 | 3.780 (5) |
O9···H3 | 2.803 (3) | N7···H61 | 3.794 (3) |
C5···O8 | 2.805 (4) | N2···O8 | 3.797 (5) |
N1···H63ii | 2.805 (3) | C5···O8 | 3.811 (5) |
N2···H63ii | 2.817 (4) | N2···H3 | 3.813 (4) |
O8···H5 | 2.830 (3) | C5···H3 | 3.828 (4) |
O8···H61 | 2.845 (3) | N7···H62 | 3.848 (3) |
C3···O9 | 2.854 (4) | C3···H62ii | 3.893 (4) |
H5···H63 | 2.8701 (4) | C6···H3 | 3.901 (4) |
O8···H63 | 2.877 (3) | N2···C6i | 3.907 (5) |
N7···H3 | 2.877 (3) | C5···N7 | 3.912 (5) |
H3···H61 | 2.9004 (3) | C3···H61 | 3.916 (3) |
H5···H61 | 2.9079 (4) | N7···H63 | 3.917 (3) |
N7···H5 | 2.911 (2) | C4···C6ii | 3.926 (5) |
H3···H62i | 2.9235 (4) | N7···H5 | 3.934 (3) |
O9···H63 | 2.937 (3) | N1···N2 | 3.939 (5) |
C3···H63ii | 3.003 (4) | C3···O8 | 3.940 (5) |
O9···H61 | 3.003 (3) | O9···H63 | 3.950 (4) |
N1···H3 | 3.029 (2) | C4···H62 | 3.957 (2) |
C5···H63ii | 3.032 (4) | C6···H3 | 3.968 (4) |
C6···O9 | 3.041 (4) | O8···H3ii | 3.972 (3) |
N2···H62i | 3.081 (3) | O8···H62 | 3.980 (3) |
N2···H5 | 3.090 (3) | C5···C6ii | 3.985 (6) |
C5···H63 | 3.125 (3) | N1···H62ii | 4.000 (3) |
C5···H3 | 3.133 (3) | O8···H62 | 4.001 (3) |
C3···H5 | 3.138 (3) | N1···O9 | 4.008 (4) |
C4···H63ii | 3.153 (3) | C4···O9 | 4.014 (5) |
C5···H61 | 3.210 (3) | N7···O9 | 4.015 (5) |
H5···H5 | 3.2290 (3) | C6···H61 | 4.025 (4) |
N7···H61 | 3.261 (3) | N2···C5 | 4.026 (5) |
H61···H63ii | 3.2631 (4) | C3···C4 | 4.060 (5) |
O9···H3ii | 3.264 (4) | C3···C5ii | 4.061 (5) |
O8···H61 | 3.270 (3) | N1···O8 | 4.070 (3) |
O8···H62 | 3.280 (4) | N1···N2 | 4.071 (4) |
O9···H3 | 3.280 (3) | C3···C6 | 4.081 (5) |
N2···H62 | 3.282 (3) | C5···C6 | 4.089 (5) |
C6···H5i | 3.286 (4) | N2···O9 | 4.109 (4) |
C3···H61 | 3.313 (3) | N2···O9 | 4.123 (4) |
N1···H5i | 3.332 (2) | N1···N7 | 4.135 (4) |
C3···H62i | 3.348 (3) | C3···O9 | 4.136 (4) |
N2···N7 | 3.353 (5) | C4···O9 | 4.177 (5) |
O8···H5 | 3.367 (4) | C4···C5 | 4.183 (5) |
O8···O9 | 3.385 (4) | C6···N7 | 4.187 (4) |
N7···H3 | 3.387 (3) | C5···N7 | 4.189 (5) |
C5···H5 | 3.389 (4) | C3···O8 | 4.201 (5) |
H3···H62 | 3.3996 (4) | C3···C3 | 4.211 (5) |
N2···C4 | 3.403 (5) | C3···C3ii | 4.211 (5) |
H5···H63 | 3.4121 (3) | C6···N7 | 4.248 (5) |
C6···O8 | 3.430 (6) | N1···C5i | 4.249 (4) |
C3···O9 | 3.431 (5) | C6···N7 | 4.250 (5) |
H5···H61 | 3.4352 (3) | N7···O8 | 4.273 (4) |
N7···O8 | 3.436 (5) | N1···C5 | 4.274 (5) |
C4···O8 | 3.438 (5) | N1···O9 | 4.295 (4) |
C6···O8i | 3.460 (4) | C3···N7 | 4.302 (4) |
C6···H63ii | 3.461 (4) | C3···C6i | 4.308 (5) |
N2···C5i | 3.465 (4) | N2···N2ii | 4.338 (5) |
C4···H61 | 3.478 (3) | N2···N2 | 4.338 (5) |
H5···H63ii | 3.4933 (3) | N1···N1ii | 4.341 (4) |
C3···C6 | 3.509 (4) | N1···N1 | 4.341 (4) |
N7···N7 | 3.521 (5) | C4···O8 | 4.345 (4) |
N1···N7 | 3.527 (3) | C6···C6 | 4.356 (6) |
N1···C3 | 3.529 (5) | C6···C6ii | 4.356 (6) |
O9···H5 | 3.531 (3) | C4···C6 | 4.421 (5) |
H3···H63ii | 3.5338 (4) | C4···C4 | 4.437 (5) |
| | | |
C5—N1—N2 | 112.4 (2) | H5—C5—C4 | 135.3 (3) |
C5—N1—C6 | 127.2 (3) | N1—C5—C4 | 106.3 (3) |
N2—N1—C6 | 120.4 (2) | H62—C6—H63 | 111.1 (4) |
C3—N2—N1 | 105.2 (2) | H62—C6—H61 | 115.8 (3) |
H3—C3—N2 | 121.1 (3) | H62—C6—N1 | 114.3 (3) |
H3—C3—C4 | 128.6 (3) | H63—C6—H61 | 91.1 (3) |
N2—C3—C4 | 110.3 (3) | H63—C6—N1 | 105.6 (3) |
C5—C4—C3 | 105.9 (2) | H61—C6—N1 | 115.9 (3) |
C5—C4—N7 | 126.4 (3) | O9—N7—O8 | 123.0 (3) |
C3—C4—N7 | 127.7 (2) | O9—N7—C4 | 118.9 (3) |
H5—C5—N1 | 118.4 (2) | O8—N7—C4 | 118.1 (2) |
| | | |
C5—N1—N2—C3 | −0.0 (4) | N1—N2—C3—H3 | 176.9 (4) |
C6—N1—N2—C3 | 179.3 (4) | N2—C3—C4—C5 | −0.3 (5) |
N2—N1—C5—C4 | −0.2 (4) | N2—C3—C4—N7 | −178.9 (4) |
N2—N1—C5—H5 | 177.8 (4) | H3—C3—C4—C5 | −176.7 (4) |
C6—N1—C5—C4 | −179.5 (4) | H3—C3—C4—N7 | 4.7 (7) |
C6—N1—C5—H5 | −1.5 (6) | C3—C4—C5—N1 | 0.3 (4) |
N2—N1—C6—H61 | −52 | C3—C4—C5—H5 | −177.1 (5) |
N2—N1—C6—H62 | 170 | N7—C4—C5—N1 | 178.9 (3) |
N2—N1—C6—H63 | 47 | N7—C4—C5—H5 | 1.5 (8) |
C5—N1—C6—H61 | 127.6 (4) | C3—C4—N7—O8 | 175.0 (4) |
C5—N1—C6—H62 | −10.9 (6) | C3—C4—N7—O9 | −5.7 (6) |
C5—N1—C6—H63 | −133.3 (4) | C5—C4—N7—O8 | −3.4 (6) |
N1—N2—C3—C4 | 0.2 (4) | C5—C4—N7—O9 | 176.0 (4) |
Symmetry codes: (i) −x, y+1/2, −z+1/2; (ii) x, −y+1/2, z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O8iii | 0.95 | 2.73 | 3.614 (4) | 155 |
C5—H5···N2iv | 0.93 | 2.56 | 3.465 (3) | 164 |
C6—H61···O9v | 1.00 | 2.63 | 3.538 (5) | 151 |
C6—H61···O8i | 1.00 | 2.85 | 3.460 (5) | 120 |
C6—H62···O9vi | 0.99 | 2.59 | 3.041 (4) | 108 |
C6—H63···O8i | 0.99 | 2.88 | 3.460 (5) | 118 |
C6—H63···N2vii | 0.99 | 2.82 | 3.546 (6) | 131 |
Symmetry codes: (i) −x, y+1/2, −z+1/2; (iii) −x+1, y+1/2, −z+3/2; (iv) −x, y−1/2, −z+1/2; (v) x−1, −y+1/2, z−1/2; (vi) x−1, y, z−1; (vii) x, −y+1/2, z−1/2. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | C4H5N3O2 | C4H5N3O2 |
Mr | 127.1 | 127.1 |
Crystal system, space group | Orthorhombic, Pnam | Monoclinic, P21/c |
Temperature (K) | 293 | 293 |
a, b, c (Å) | 10.5062 (5), 8.5940 (4), 6.3562 (3) | 7.4197 (8), 10.1803 (15), 8.3529 (10) |
α, β, γ (°) | 90, 90, 90 | 90, 112.924 (8), 90 |
V (Å3) | 573.90 (5) | 581.11 (13) |
Z | 4 | 4 |
Radiation type | Cu Kα | Cu Kα |
µ (mm−1) | 1.04 | 1.03 |
Crystal size (mm) | 0.60 × 0.50 × 0.23 | 0.50 × 0.33 × 0.23 |
|
Data collection |
Diffractometer | Philips PW1100 four-circle diffractometer | Philips PW1100 four-circle four-circle diffractometer |
Absorption correction | ψ-scan (North et al., 1968) | ψ-scan (North et al., 1968) |
Tmin, Tmax | 0.518, 0.788 | 0.569, 0.790 |
No. of measured, independent and observed reflections | 1164, 571, 571 (I > 0) | 1181, 1011, 854 [I > 0.75σ(I)] |
Rint | 0.044 | 0.059 |
(sin θ/λ)max (Å−1) | 0.599 | 0.599 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.043, 0.045, 1.02 | 0.071, 0.08, 1.00 |
No. of reflections | 571 | 854 |
No. of parameters | 56 | 83 |
H-atom treatment | H-atom parameters not refined | H-atom parameters not refined |
Δρmax, Δρmin (e Å−3) | 0.22, −0.19 | 0.32, −0.32 |
Selected geometric parameters (Å, º) for (I) topN1—N2 | 1.335 (2) | C3—C4 | 1.383 (3) |
N1—C5 | 1.344 (3) | C3—N7 | 1.445 (3) |
N1—C6 | 1.450 (3) | C4—C5 | 1.358 (4) |
N2—C3 | 1.319 (3) | | |
| | | |
N2—N1—C5 | 112.3 (2) | C4—C3—N7 | 127.1 (2) |
C3—N2—N1 | 103.2 (2) | C5—C4—C3 | 103.0 (2) |
N2—C3—C4 | 113.8 (2) | N1—C5—C4 | 107.7 (2) |
N2—C3—N7 | 119.2 (2) | | |
| | | |
N2—N1—C6—H61 | 180 | N2—C3—N7—O8 | 0.0 (2) |
N2—N1—C6—H62 | 60 | | |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
C4—H4···O8i | 0.97 | 2.57 | 3.527 (3) | 170 |
C6—H61···O8ii | 0.97 | 2.55 | 3.489 (3) | 163 |
Symmetry codes: (i) x+1/2, −y+3/2, −z+1/2; (ii) x+1/2, −y+1/2, −z+1/2. |
Selected geometric parameters (Å, º) for (II) topN1—C5 | 1.323 (4) | C3—C4 | 1.397 (4) |
N1—N2 | 1.360 (4) | C4—C5 | 1.369 (4) |
N1—C6 | 1.453 (4) | C4—N7 | 1.412 (4) |
N2—C3 | 1.315 (4) | | |
| | | |
C5—N1—N2 | 112.4 (2) | C5—C4—N7 | 126.4 (3) |
C3—N2—N1 | 105.2 (2) | C3—C4—N7 | 127.7 (2) |
N2—C3—C4 | 110.3 (3) | N1—C5—C4 | 106.3 (3) |
C5—C4—C3 | 105.9 (2) | | |
| | | |
N2—N1—C6—H61 | −52 | C3—C4—N7—O9 | −5.7 (6) |
N2—N1—C6—H62 | 170 | C5—C4—N7—O8 | −3.4 (6) |
N2—N1—C6—H63 | 47 | | |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
C3—H3···O8i | 0.95 | 2.73 | 3.614 (4) | 155 |
C5—H5···N2ii | 0.93 | 2.56 | 3.465 (3) | 164 |
C6—H61···O9iii | 1.00 | 2.63 | 3.538 (5) | 151 |
C6—H61···O8iv | 1.00 | 2.85 | 3.460 (5) | 120 |
C6—H62···O9v | 0.99 | 2.59 | 3.041 (4) | 108 |
Symmetry codes: (i) −x+1, y+1/2, −z+3/2; (ii) −x, y−1/2, −z+1/2; (iii) x−1, −y+1/2, z−1/2; (iv) −x, y+1/2, −z+1/2; (v) x−1, y, z−1. |
As part of our ongoing study of the relationship between the molecular and crystal structures of pyrazole derivatives, crystal structure determinations of 1-methyl-3-nitropyrazole, (I), and 1-methyl-4-nitropyrazole, (II), have been undertaken. N-unsubstituted pyrazoles with only one potential donor and one potential acceptor in the ring form dimers, trimers, tetramers or catemers through N—H···N hydrogen bonds. In the nitropyrazole derivatives already studied (Llamas-Saiz et al., 1994; Foces-Foces et al., 1994, 1997), C—H···O interactions are responsible for the cohesion of these motifs, giving rise to the formation of layered structures. The main aim of this work is to study the influence of the nitro group, not only on the molecular structure but on the crystal packing, when there are several hydrogen-bond acceptors in the molecule and the only hydrogen bond donor in the pyrazole (N—H) has been replaced by a methyl group. \scheme
In the present compounds, the nitro group attached to either the C3 atom, (I), or the C4 atom, (II), of the pyrazole ring (Fig. 1a and Fig. 1 b) mainly affects the molecular structure, while the crystal packing, in layers, is similar. The differences at the molecular level concern the bond distance and angle patterns and the planarity of the molecule as a whole. In (I), all non-H atoms are coplanar (the molecules lie on mirror planes), while in (II) the pyrazole and the nitro group are slightly twisted with respect to each other, the angle between their planes being 4.5 (2)°. The significant differences in bond lengths and angles in the pyrazole ring (Tables 1 and 3) can be ascribed to the electron properties of the nitro group, resulting in an opening of the corresponding internal angle of the pyrazole and a closing of the adjacent ones. These angular deformations are in good agreement with those observed for nitrobenzenes and nitropyrazoles from an experimental and theoretical (ab initio) point of view (Domenicano & Murray-Rust, 1979; Llamas-Saiz et al., 1994; Foces-Foces et al., 1997).
A search of the Cambridge Structural Database (Allen et al., 1991, version of April 1999, CSD hereinafter) for 3- or 4-nitropyrazole derivatives yields just a few organic structures without disorder, three and ten structures (nine and 18 fragments), respectively. The molecules reported so far (CSD) display the following features. Firstly, the 3-nitro derivatives display a different bonding pattern from that of the 4-nitro ones and both patterns agree with those found in (I) and (II), respectively. Secondly, the nitro group is almost coplanar with the pyrazole ring, although it can be twisted by up to 87° (CSD reference TASJEC; Dalinger et al., 1996) to lessen the steric interactions when substituents other than H atoms are placed at adjacent positions. Thirdly, in spite of the dispersion of the samples, the C—N(NO2) distance appears to be longer in the 3-nitro than in the 4-nitro derivatives reported so far, and this may be due to steric hindrance [1.447 (22) and 1.431 (13) Å, respectively, for the average and the standard deviation of the sample]. This distance is significantly longer in (I) (C3—N7) than in (II) (C4—N7); see Tables 1 and 3. Fourthly, for either the 3- or 4-nitro, treated individually, the C—N(NO2) distance is correlated with the twist of the nitro group with respect to the pyrazole: the greater the N—C—N—O or C—C—N—O angle the larger the C—N distance. This observation is consistent with the theoretical ab initio results on 4-nitropyrazole (Llamas-Saiz et al., 1994) as a consequence of the resonance interaction. Finally, in the 3-nitro derivatives, the C4—C3—N7 angle is significantly widened, reducing the corresponding N2—C3—N7 angle. In the 4-nitro derivatives both angles are quite similar.
The crystal packing in the two structures is remarkably similar. The molecules pack in layers (Fig. 2a and Fig. 2 b), although the planarity of these layers is slightly different, as seen in Fig. 1. The two-dimensional network is formed by C—H···N and C—H···O interactions, in which the closest intermolecular interaction occurs between the methyl group and O9 (Tables 2 and 4). In this contact, the C···O distance is ca 0.2 Å shorter than the sum of the corresponding van der Waals radii [rw(C) = 1.70 and rw(O) = 1.52 Å; Vainshtein et al., 1982], although the angle at H is very narrow. The differences within the layers concern their planarity and the disposition of the donor (A) and acceptor groups (D) in the molecule. In (I), the molecules lie on planes perpendicular to the c axis (Fig. 2a) and all donor groups, and therefore all acceptor groups, are located on one side or the other of the molecule following the sequence DDD or AAA, respectively (Fig. 1a). In (II), the molecules forming a sheet lie approximately in planes perpendicular to the ac plane and contiguous molecules make angles of 15.7 (1)° (Fig. 2 b). In addition, the donor-acceptor sequences are DAD or ADA (Fig. 1 b), which could be coincident with those for (I) if the N2 and C5 atoms interchanged their positions in the pyrazole ring. However, differences of up to 0.3 Å (?) in the equivalent H···O and H···N distances are observed, for instance H5···N2 and H62···O9 in (I), and H3···O8 and H61···O8 in (II) (Fig. 1, and Tables 2 and 4). The layers in (I) are connected only by van der Waals interactions, whereas in (II) the O9 atom links layers through C—H···O contacts (Table 4); the lack of this interaction in (I) could be due to gliding between layers. The thickness of the layers in (I) is 3.178 Å (c/2), while in (II) it is 3.289 Å, computed from the number of sheets along the (a-c) diagonal distance (Fig.2 b).
In summary, comparing the crystal structures of (II) and (I), the positioning of the nitro group at C3 [(I)] instead of at C4 [(II)] is accompanied by an increase of the symmetry within the layers (molecules on mirror planes), which implies a change from a monoclinic [(II)] to an orthorhombic lattice [(I)], followed by an increase of the beta angle; the n-glide plane perpendicular to the 10 Å axis, as well as the twofold screw axis parallel to it, are maintained in both structures.