3-Methyl-3-pyrazolin-5-one

The title compound, C₄H₆N₂O, is an intermediate in the further synthesis of theterocyclic compounds. The present crystal structure is orthorhombic (space group Fdd2), and a monoclinic form (P2₁/a) has been reported by De Camp & Stewart [(1971). Acta Cryst. B27, 1227-1232].

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.005 Å
• R factor = 0.043
• wR factor = 0.115
• Data-to-parameter ratio = 7.0

checkCIF/PLATON results

No syntax errors found



Alert level B
ABSTM02_ALERT_3_B  The ratio of expected to reported Tmax/Tmin(RR') is < 0.75
            Tmin and Tmax reported:      0.557     0.981
            Tmin' and Tmax expected:      0.970     0.980
            RR' =      0.574
            Please check that your absorption correction is appropriate.
PLAT061_ALERT_3_B Tmax/Tmin Range Test RR' too Large .............       0.57

Alert level C
PLAT024_ALERT_4_C Merging of Friedel Data Preferred for Z<=Si ....          !
PLAT031_ALERT_4_C Refined Extinction Parameter within Range ......       2.50 Sigma
PLAT089_ALERT_3_C Poor Data / Parameter Ratio (Zmax .LT. 18) .....       6.97
PLAT125_ALERT_4_C No _symmetry_space_group_name_Hall Given .......          ?
PLAT152_ALERT_1_C Supplied and Calc Volume s.u. Inconsistent .....          ?
PLAT340_ALERT_3_C Low Bond Precision on C-C bonds (x 1000) Ang ...          5

Alert level G
REFLT03_ALERT_4_G 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.
           From the CIF: _diffrn_reflns_theta_max           25.00
           From the CIF: _reflns_number_total                460
           Count of symmetry unique reflns          459
           Completeness (_total/calc)            100.22%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured         1
           Fraction of Friedel pairs measured     0.002
           Are heavy atom types Z>Si present           no

   0 ALERT level A = In general: serious problem
   2 ALERT level B = Potentially serious problem
   6 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   4 ALERT type 3 Indicator that the structure quality may be low
   4 ALERT type 4 Improvement, methodology, query or suggestion

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Computing details

Data collection: SMART (Bruker, 2000); cell refinement: SAINT (Bruker, 2000); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL/PC (Sheldrick, 1999); software used to prepare material for publication: SHELXTL/PC.

3-Methyl-3-Pyrazolin-5-one

Crystal data

C4H6N2O	Dx = 1.326 Mg m^−3
Mr = 98.11	Melting point: 215 K
Orthorhombic, Fdd2	Mo Kα radiation, λ = 0.71073 Å
a = 11.722 (2) Å	Cell parameters from 867 reflections
b = 16.945 (3) Å	θ = 5.9–44.4°
c = 9.898 (2) Å	µ = 0.10 mm^−1
V = 1966.0 (7) Å^3	T = 293 K
Z = 16	Block, colorless
F(000) = 832	0.30 × 0.20 × 0.20 mm

Data collection

Smart CCD diffractometer	460 independent reflections
Radiation source: fine-focus sealed tube	439 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.034
ω scan	θmax = 25.0°, θmin = 3.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −13→13
Tmin = 0.557, Tmax = 0.981	k = −20→9
1933 measured reflections	l = −11→11

Refinement

Refinement on F^2	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F^2 > 2σ(F^2)] = 0.043	w = 1/[σ^2(Fo^2) + (0.063P)^2 + 1.0082P] where P = (Fo^2 + 2Fc^2)/3
wR(F^2) = 0.115	(Δ/σ)max = 0.011
S = 1.16	Δρmax = 0.13 e Å^−3
460 reflections	Δρmin = −0.16 e Å^−3
66 parameters	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
1 restraint	Extinction coefficient: 0.0020 (8)
Primary atom site location: structure-invariant direct methods	Absolute structure: see text
Secondary atom site location: difference Fourier map

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.9969 (2)	0.38889 (15)	0.3766 (3)	0.0597 (9)
N1	0.9383 (3)	0.21227 (16)	0.5257 (3)	0.0489 (9)
H1	0.8992	0.1829	0.5794	0.059*
N2	0.9171 (3)	0.28983 (16)	0.4984 (3)	0.0464 (9)
H2	0.8611	0.3168	0.5303	0.056*
C1	1.0662 (5)	0.1058 (2)	0.4573 (6)	0.0750 (15)
H1A	1.0528	0.0834	0.5450	0.113*
H1B	1.1461	0.1031	0.4366	0.113*
H1C	1.0240	0.0767	0.3907	0.113*
C2	1.0284 (3)	0.1899 (2)	0.4565 (4)	0.0456 (9)
C3	1.0689 (3)	0.2535 (2)	0.3862 (4)	0.0481 (10)
H3	1.1326	0.2545	0.3301	0.058*
C4	0.9962 (3)	0.3171 (2)	0.4151 (4)	0.0435 (9)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0520 (15)	0.0400 (15)	0.087 (2)	0.0018 (12)	0.0107 (14)	0.0231 (14)
N1	0.068 (2)	0.0273 (15)	0.0514 (18)	−0.0046 (13)	0.0136 (16)	0.0091 (13)
N2	0.0478 (17)	0.0296 (15)	0.062 (2)	0.0035 (12)	0.0154 (14)	0.0064 (13)
C1	0.101 (4)	0.043 (2)	0.081 (3)	0.025 (2)	0.008 (3)	0.003 (2)
C2	0.055 (2)	0.040 (2)	0.0419 (17)	0.0078 (16)	−0.0005 (16)	−0.0021 (16)
C3	0.041 (2)	0.053 (2)	0.0502 (19)	0.0032 (16)	0.0044 (16)	0.0086 (17)
C4	0.0385 (17)	0.041 (2)	0.051 (2)	0.0032 (14)	0.0016 (16)	0.0068 (17)

Geometric parameters (Å, º)

O1—C4	1.275 (3)	C1—H1A	0.9600
N1—C2	1.315 (5)	C1—H1B	0.9600
N1—N2	1.365 (4)	C1—H1C	0.9600
N1—H1	0.8600	C2—C3	1.368 (5)
N2—C4	1.324 (4)	C3—C4	1.403 (5)
N2—H2	0.8600	C3—H3	0.9300
C1—C2	1.493 (4)
C2—N1—N2	108.7 (3)	H1B—C1—H1C	109.5
C2—N1—H1	125.7	N1—C2—C3	108.5 (3)
N2—N1—H1	125.7	N1—C2—C1	120.7 (4)
C4—N2—N1	109.4 (3)	C3—C2—C1	130.7 (4)
C4—N2—H2	125.3	C2—C3—C4	106.8 (3)
N1—N2—H2	125.3	C2—C3—H3	126.6
C2—C1—H1A	109.5	C4—C3—H3	126.6
C2—C1—H1B	109.5	O1—C4—N2	121.6 (3)
H1A—C1—H1B	109.5	O1—C4—C3	131.8 (3)
C2—C1—H1C	109.5	N2—C4—C3	106.6 (3)
H1A—C1—H1C	109.5

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1^i	0.86	1.93	2.694 (4)	148
N2—H2···O1^ii	0.86	1.81	2.654 (4)	169

Symmetry codes: (i) −x+7/4, y−1/4, z+1/4; (ii) x−1/4, −y+3/4, z+1/4.