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The title compound, C8H14N2, exists in the solid state as a tetramer with hydrogen bonding around the \overline 4 axis.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536800018511/cf6000sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536800018511/cf6000Isup2.hkl
Contains datablock I

CCDC reference: 155877

Key indicators

  • Single-crystal X-ray study
  • T = 240 K
  • Mean [sigma](C-C) = 0.007 Å
  • R factor = 0.088
  • wR factor = 0.117
  • Data-to-parameter ratio = 11.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Red Alert Alert Level A:
PLAT_601 Alert A Structure contains solvent accessible VOIDS of 442.00 A   3
Author response: There are four voids in the structure located at (0,0,1/2) and equivalent positions, spherical in shape and of 3.5\%A diameter approximately (Cano & Martinez-Ripoll, 1992). According to the ^1^H and ^13^C NMR experiments no solvent molecules were detected. Futhermore, no residual electron density was found for ordered water. This paragraph has been included in the experimental section

Yellow Alert Alert Level C:
THETM_01 Alert C The value of sine(theta_max)/wavelength is less than 0.590 Calculated sin(theta_max)/wavelength = 0.5878 General Notes
REFLT_03 From the CIF: _diffrn_reflns_theta_max 65.00 From the CIF: _reflns_number_total 1509 Count of symmetry unique reflns 1511 Completeness (_total/calc) 99.87% TEST3: Check Friedels for noncentro structure Estimate of Friedel pairs measured 0 Fraction of Friedel pairs measured 0.000 Are heavy atom types Z>Si present no Please check that the estimate of the number of Friedel pairs is correct. If it is not, please give the correct count in the _publ_section_exptl_refinement section of the submitted CIF.
1 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

One of our interests in crystalline pyrazoles involves elucidation of factors controlling the four intermolecular hydrogen-bonding modes (catemers, dimers, trimers and tetramers) that have been found in pyrazoles bearing only one conventional donor and/or including other acceptor groups apart from that of the pyrazole (Foces-Foces et al., 2000). In the three 3,5-di-tert-butylpyrazole derivatives studied so far (with substituents at C4NO2, H and NO; Llamas-Saiz et al., 1994; Aguilar-Parrilla et al., 1995; Fletcher et al., 1997; CSD refcodes WILBAU, YULNUO and RIVBAZ, respectively), the dimeric association is the only hydrogen-bonding mode observed. The aim of this paper is to study the contribution of different types of substituents on the secondary structure (one methyl group at C3 instead of a tert-butyl group) which appear to govern the choice of a hydrogen-bonding mode.

It is noteworthy that the 5-tert-butyl-3-methyl-1H-pyrazole tautomer, (I), is present in the solid state (Fig. 1) in spite of the tendency of these compounds to present proton disorder. The bond distances and angles in the ring are unremarkable with respect to those of the undisordered proton derivatives and the parent compound (i.e. N2—N1—C5 > N1—N2—C3; N2—C3—C4 > N1—C5—C4). The conformation of the tert-butyl group places the methyl C10 eclipsed with respect to the H4 atom whereas, in the previous reported derivatives with substituents at C4, one methyl group is eclipsed with respect to the the N atoms to avoid steric repulsions (Table 1).

An intermolecular hydrogen bond between the N atoms of the pyrazole (Table 2) leads to the formation of tetramers, around the 4 axis (Figs. 2 and 3), in agreement with the proposed secondary structure model (Foces-Foces et al., 2000) for methyl and butyl substituents at C3 and C5.

Experimental top

The title compound was prepared according to López et al. (1993) and crystals were obtained by recrystallization from cyclohexane. The melting point (440 K) was determined by DSC with a Seiko 220 C instrument with a scanning rate of 2° min-1.

Refinement top

Considering the possibility of disorder of the tert-butyl group the data were collected at 240 K using an Oxford Cryostream device (Cosier & Glazer, 1986) and the stated temperature was measured continuously during data collection. Due to the disposition of the low-temperature device, the maximum θ angle available is 65°. Rotational disorder of the tert-butyl group around the C5—C7 bond was apparent from their large displacement parameters; however, attemps to establish a disordered model failed. The highest peaks of 0.39 e Å-3 in the final difference synthesis are close to the tert-butyl group. All H atoms were obtained from difference Fourier synthesis although only H1 was refined freely; others were constrained. The weighting schemes were established in an empirical way as to give no trends in <wΔ2F> versus <Fo> or <sinθ/λ>, using different parameters in the weighting formula for different ranges of these variables (PESOS; Martínez-Ripoll & Cano, 1975). There are four voids in the structure located at (0,0,1/2) and equivalent positions, spherical in shape and of 3.5 Å diameter approximately (Cano & Martinez-Ripoll, 1992). According to the 1H and 13C NMR experiments no solvent molecules were detected. The calculated density for the title compound is in the range found for the analogous derivatives (WILBAU, YULNUO, RIVBAZ).

Computing details top

Data collection: Philips PW1100 (Hornstra & Vossers, 1973); cell refinement: LSUCRE (Appleman, 1984); data reduction: Xtal3.6 ADDREF DIFDAT SORTRF (Hall et al., 1999); program(s) used to solve structure: SIR97 (Altomare et al., 1997); program(s) used to refine structure: Xtal3.6 CRYLSQ; molecular graphics: Xtal3.6; software used to prepare material for publication: Xtal3.6 BONDLA CIFIO.

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) showing the numbering scheme. The displacement parameters are drawn at the 30% probability level.
[Figure 2] Fig. 2. The tetrameric arrangement of molecules around the 4 axis. Dotted lines represent hydrogen bond interactions.
[Figure 3] Fig. 3. The crystal packing viewed along the c axis.
(I) top
Crystal data top
C8H14N2Dx = 1.034 Mg m3
Mr = 138.21Melting point: 440 K
Tetragonal, I41/aCu Kα radiation, λ = 1.54178 Å
Hall symbol: i 4bw -1bwCell parameters from 56 reflections
a = 18.2451 (16) Åθ = 2–45°
c = 10.6667 (8) ŵ = 0.48 mm1
V = 3550.8 (7) Å3T = 240 K
Z = 16Prism, colourless
F(000) = 12160.50 × 0.10 × 0.10 mm
Data collection top
Philips PW100
diffractometer
θmax = 65.0°, θmin = 4.8°
ω/2θ scansh = 021
1509 measured reflectionsk = 021
1509 independent reflectionsl = 012
1100 reflections with I > 2σ(I)2 standard reflections every 90 min
Rint = 0 intensity decay: 3%
Refinement top
Refinement on F39 restraints
Least-squares matrix: full0 constraints
R[F2 > 2σ(F2)] = 0.088H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.117 w = k/[(A + B Fo)2(C + D(sinθ)/λ)]
S = 0.98(Δ/σ)max = 0.005
1100 reflectionsΔρmax = 0.39 e Å3
95 parametersΔρmin = 0.31 e Å3
Crystal data top
C8H14N2Z = 16
Mr = 138.21Cu Kα radiation
Tetragonal, I41/aµ = 0.48 mm1
a = 18.2451 (16) ÅT = 240 K
c = 10.6667 (8) Å0.50 × 0.10 × 0.10 mm
V = 3550.8 (7) Å3
Data collection top
Philips PW100
diffractometer
Rint = 0
1509 measured reflections2 standard reflections every 90 min
1509 independent reflections intensity decay: 3%
1100 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.08839 restraints
wR(F2) = 0.117H atoms treated by a mixture of independent and constrained refinement
S = 0.98Δρmax = 0.39 e Å3
1100 reflectionsΔρmin = 0.31 e Å3
95 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.09449 (18)0.05360 (17)0.1151 (3)0.0460 (17)
N20.11979 (18)0.01379 (18)0.0895 (3)0.0488 (17)
C30.1543 (2)0.0360 (2)0.1941 (4)0.047 (2)
C40.1507 (2)0.0196 (2)0.2839 (3)0.0465 (18)
C50.11229 (19)0.0765 (2)0.2320 (3)0.0414 (17)
C60.1890 (3)0.1091 (3)0.2021 (5)0.066 (3)
C70.0867 (2)0.1487 (2)0.2826 (4)0.053 (2)
C80.1125 (6)0.2115 (3)0.1989 (7)0.103 (5)
C90.0034 (4)0.1513 (4)0.2832 (9)0.107 (5)
C100.1156 (5)0.1603 (4)0.4139 (6)0.106 (5)
H10.068 (3)0.082 (3)0.0587 (5)0.032 (12)*
H40.17270.01800.37380.047*
H6a0.15640.14670.15450.050*
H6b0.19420.12450.29550.066*
H6c0.24080.10690.16160.066*
H8a0.08820.20660.11100.066*
H8b0.16920.20950.19000.104*
H8c0.09730.26120.23900.104*
H9a0.01430.20170.31700.104*
H9b0.01610.14410.19230.107*
H9c0.01640.10970.34050.107*
H10a0.10040.11640.47040.107*
H10b0.09400.20870.45010.107*
H10c0.17250.16390.41200.107*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0526 (17)0.0477 (17)0.0377 (16)0.0048 (13)0.0070 (13)0.0020 (12)
N20.0527 (18)0.0520 (18)0.0416 (16)0.0052 (13)0.0041 (13)0.0062 (13)
C30.0441 (18)0.049 (2)0.049 (2)0.0001 (14)0.0007 (15)0.0011 (15)
C40.0498 (19)0.048 (2)0.0416 (18)0.0038 (14)0.0069 (15)0.0015 (15)
C50.0434 (17)0.0443 (18)0.0366 (17)0.0030 (13)0.0033 (13)0.0018 (13)
C60.073 (3)0.054 (2)0.072 (3)0.005 (2)0.008 (2)0.002 (2)
C70.059 (2)0.051 (2)0.048 (2)0.0065 (15)0.0033 (17)0.0055 (16)
C80.163 (7)0.053 (3)0.095 (4)0.009 (3)0.032 (4)0.004 (3)
C90.072 (3)0.095 (4)0.153 (7)0.010 (3)0.005 (4)0.053 (5)
C100.161 (7)0.085 (4)0.073 (4)0.047 (4)0.044 (4)0.034 (3)
Geometric parameters (Å, º) top
N1—H10.93 (5)C7—C101.513 (8)
N1—N21.342 (5)C7—C91.521 (8)
N1—C51.354 (5)C7—C81.527 (8)
N2—C31.344 (5)C8—H8c1.040
C3—C41.396 (5)C8—H8b1.040
C3—C61.479 (6)C8—H8a1.040
C4—H41.040C9—H9a1.040
C4—C51.370 (5)C9—H9c1.040
C5—C71.498 (5)C9—H9b1.040
C6—H6b1.040C10—H10a1.040
C6—H6c1.040C10—H10c1.040
C6—H6a1.040C10—H10b1.040
H1—N1—N2124 (3)C10—C7—C9109.9 (6)
H1—N1—C5123 (3)C10—C7—C8109.2 (5)
N2—N1—C5112.8 (3)C9—C7—C8106.7 (6)
N1—N2—C3105.5 (3)H8c—C8—H8b109.4
N2—C3—C4109.2 (3)H8c—C8—H8a109.4
N2—C3—C6121.3 (4)H8c—C8—C7109.4
C4—C3—C6129.4 (4)H8b—C8—H8a109.8
H4—C4—C5126.2H8b—C8—C7109.5
H4—C4—C3126.5H8a—C8—C7109.4
C5—C4—C3107.3 (3)H9a—C9—H9c109.5
N1—C5—C4105.1 (3)H9a—C9—H9b109.3
N1—C5—C7121.9 (3)H9a—C9—C7109.8
C4—C5—C7132.9 (3)H9c—C9—H9b109.7
H6b—C6—H6c109.0H9c—C9—C7109.0
H6b—C6—H6a109.9H9b—C9—C7109.4
H6b—C6—C3109.8H10a—C10—H10c109.2
H6c—C6—H6a110.0H10a—C10—H10b109.7
H6c—C6—C3109.2H10a—C10—C7109.6
H6a—C6—C3108.9H10c—C10—H10b109.6
C5—C7—C10110.4 (4)H10c—C10—C7109.5
C5—C7—C9110.0 (4)H10b—C10—C7109.3
C5—C7—C8110.7 (4)
C5—N1—N2—C31.0 (4)C5—C7—C8—H8a64.2
H1—N1—N2—C3180 (4)C5—C7—C8—H8b56.1
N2—N1—C5—C40.7 (4)C5—C7—C8—H8c176.0
N2—N1—C5—C7177.1 (3)C9—C7—C8—H8a55.4
H1—N1—C5—C4180 (4)C9—C7—C8—H8b175.7
H1—N1—C5—C74 (4)C9—C7—C8—H8c64.4
N1—N2—C3—C40.9 (4)C10—C7—C8—H8a174.1
N1—N2—C3—C6179.2 (4)C10—C7—C8—H8b65.6
N2—C3—C4—C50.5 (4)C10—C7—C8—H8c54.3
N2—C3—C4—H4179.8C5—C7—C9—H9a179.1
C6—C3—C4—C5179.6 (4)C5—C7—C9—H9b59.2
C6—C3—C4—H40.1C5—C7—C9—H9c60.8
N2—C3—C6—H6a37.4C8—C7—C9—H9a59.1
N2—C3—C6—H6b157.8C8—C7—C9—H9b60.9
N2—C3—C6—H6c82.7C8—C7—C9—H9c179.1
C4—C3—C6—H6a142.7C10—C7—C9—H9a59.1
C4—C3—C6—H6b22.3C10—C7—C9—H9b179.1
C4—C3—C6—H6c97.1C10—C7—C9—H9c60.9
C3—C4—C5—N10.1 (4)C5—C7—C10—H10a55.4
C3—C4—C5—C7175.9 (4)C5—C7—C10—H10b175.6
H4—C4—C5—N1179.7C5—C7—C10—H10c64.4
H4—C4—C5—C73.8C8—C7—C10—H10a177.2
N1—C5—C7—C858.2 (6)C8—C7—C10—H10b62.5
N1—C5—C7—C959.4 (6)C8—C7—C10—H10c57.5
N1—C5—C7—C10179.2 (5)C9—C7—C10—H10a66.1
C4—C5—C7—C8126.5 (6)C9—C7—C10—H10b54.1
C4—C5—C7—C9115.9 (6)C9—C7—C10—H10c174.2
C4—C5—C7—C105.5 (7)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···N2i0.93 (5)1.99 (6)2.896 (5)165 (5)
Symmetry code: (i) y, x, z.

Experimental details

Crystal data
Chemical formulaC8H14N2
Mr138.21
Crystal system, space groupTetragonal, I41/a
Temperature (K)240
a, c (Å)18.2451 (16), 10.6667 (8)
V3)3550.8 (7)
Z16
Radiation typeCu Kα
µ (mm1)0.48
Crystal size (mm)0.50 × 0.10 × 0.10
Data collection
DiffractometerPhilips PW100
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
1509, 1509, 1100
Rint0
(sin θ/λ)max1)0.588
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.088, 0.117, 0.98
No. of reflections1100
No. of parameters95
No. of restraints39
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.39, 0.31

Computer programs: Philips PW1100 (Hornstra & Vossers, 1973), LSUCRE (Appleman, 1984), Xtal3.6 ADDREF DIFDAT SORTRF (Hall et al., 1999), SIR97 (Altomare et al., 1997), Xtal3.6 CRYLSQ, Xtal3.6 BONDLA CIFIO.

Selected bond and torsion angles (º) top
N2—N1—C5112.8 (3)N2—C3—C4109.2 (3)
N1—N2—C3105.5 (3)N1—C5—C4105.1 (3)
N1—C5—C7—C858.2 (6)N1—C5—C7—C10179.2 (5)
N1—C5—C7—C959.4 (6)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···N2i0.93 (5)1.99 (6)2.896 (5)165 (5)
Symmetry code: (i) y, x, z.
 

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