4-Acetyl-5-methyl-2-phenyl-1,2-di­hydro-3H-pyrazol-3-one hydrate

The title compound, C₁₂H₁₂O₂N₂·H₂O, is described. Although the keto-enol form of the ligand in solution is known, the compound crystallized in the orthorhombic space group P2₁2₁2₁ with only the monohydrated 1,3-diketo form. The intermolecular hydrogen bond between the imino N-H group of the ligand and O atom of the water mol­ecule recorded an H...O distance of 1.73 (3) Å.

S1. Comment

4-Acetyl-5-methyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one hydrate, (I), has been of versatile application in the extraction of transition metal ions from aqueous media (Bukowsky et al., 1992; Uzoukwu et al., 1998). The nature of the ligand in solution and its mode of interaction with metal ions have been studied mainly by spectroscopic methods (Okafor, 1984; Uzoukwu, 1995) because crystals of the ligand that are suitable for X-ray diffraction studies have been very difficult to obtain. Hence, X-ray diffraction studies of its complexes with metal ions have appeared in the literature (Pettinari et al., 1994, 1998) with no X-ray diffraction report on the elusive structure of the ligand. No reference of a demonstrated method of obtaining good crystal form of (I) is apparently available. We report here the X-ray data of (I) and also a method for getting good crystals of the ligand. \scheme

Some selected bond length and angles of (I) are given in Table 1. The compound crystallized with a structural configuration in which the phenyl ring is twisted with a dihedral angle of 37.82 (6)° with respect to a plane defined by the pyrazole ring. The pyrazole ring and the O1/C4/C3/C11/O2 plane are nearly coplanar [dihedral angle 3.18 (14)°]. The C4═O1 carbonyl group usually participates in intraligand hydrogen bonding within the chelate ring of the ketoenol tautomer. In (I), it has a bond distance of 1.257 (3) Å that is much shorter than 1.319 (5) and 1.323 (3) Å reported for C—O single bond of the corresponding carbonyl groups in the 4-butanoyl (Uzoukwu et al., 1993) and 4-benzyol derivatives (Akama et al., 1995), respectively. This shows the double bond nature of the C4═O1 bond. The other carbonyl group, C11═O2, with a bond distance of 1.216 (3) Å is also shorter than the 1.256 (6) and 1.247 (3) Å reported for the corresponding carbonyl groups in the 4-butanoyl (Uzoukwu et al., 1993) and 4-benzyol derivatives, and it has an approximate 180° orientation from the position of these carbonyl groups as well. The reduction in the bond distances of both carbonyl groups has been associated with the strain around the C11—C3—C2 and C11—C3—C4 carbon skeletons as a result of the close to 180° twist of the acyl group along the C3—C11 bond axis during the formation of the diketo tautomer. This may account for the longer N2—C4 bond distance of 1.375 (3) Å when compared with 1.348 (3) Å reported for a similar bond. There is an imino–water N—H···O intermolecular hydrogen bonding between the NH group of the ligand and water molecule, with an O3···H1 distance of 1.73 (3) Å. This intermolecular hydrogen bond is probably the most important bond formation that stabilized the crystallization of the compound as a 1,3-diketone rather than as a 1,3-ketoenol.

The UV spectrum of the compound in chloroform exhibited two absorption bands at 250 nm and 286 nm assigned to intramolecular π to π* transitions. The IR spectrum indicated a very strong asymmetric C═O stretching frequency at 1635 cm⁻¹. Vibrational frequency bands due to O—H group of the water molecule appeared at 3300 cm⁻¹ as a broad band. Another broad band centred at 2500 cm⁻¹ has been assigned to stretching frequency of the intermolecular N—H···O hydrogen bond. The ¹H NMR data, however, showed that in an organic solvent the ligand rearranges to the ketoenol form with C4—O1—H species, for which the singlet at 10.38 p.p.m. was assigned to the O—H proton.

S2. Experimental

Compound (I) was synthesized and purified as reported elsewhere (Jensen, 1959). The diketo crystal was grown as follows. A warm ethanol solution of the ligand (1 g in 50 ml) was obtained. Warm water (200 ml) was poured into the ethanol solution and the white suspension was decanted. It was redissolved in 200 ml of warm water in a beaker with addition of drops of ethanol, covered with a dish and kept aside for one week for the crystals to grow.

S3. Refinement

Friedel pairs were merged because anomalous dispersion effects are negligible. The H atoms bonded to N and O were located in difference Fourier maps and refined freely isotropically [N—H = 0.97 (3) Å, and O—H = 0.82 (5) and 0.84 (4) Å], all other were included in the refinement in calculated positions (C—H = 0.93 and 0.96 Å), riding on their carrier atoms.

Computing details

Data collection: CAD-4 EXPRESS (Nonius, 1992); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4/PC (Harms, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997a); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997b); software used to prepare material for publication: SHELXL97.

4-Acetyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazole-3-one hydrate

Crystal data

C12H12N2O2·H2O	Dx = 1.278 Mg m^−3
Mr = 234.25	Melting point: 331 K
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
a = 7.419 (4) Å	Cell parameters from 25 reflections
b = 7.522 (4) Å	θ = 19.8–28.2°
c = 21.814 (8) Å	µ = 0.09 mm^−1
V = 1217.2 (10) Å^3	T = 293 K
Z = 4	Prism, colourless
F(000) = 496	1.0 × 0.58 × 0.58 mm

Data collection

Nonius CAD-4 diffractometer	Rint = 0.043
Radiation source: fine-focus sealed tube	θmax = 25.0°, θmin = 3.3°
Graphite monochromator	h = −8→8
ω/2θ scans	k = −8→0
2346 measured reflections	l = −25→0
2130 independent reflections	3 standard reflections every 400 reflections
1907 reflections with I > 2σ(I)	intensity decay: 4%

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.037	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.103	w = 1/[σ^2(Fo^2) + (0.06P)^2 + 0.0872P] where P = (Fo^2 + 2Fc^2)/3
S = 1.06	(Δ/σ)max = 0.001
1264 reflections	Δρmax = 0.16 e Å^−3
167 parameters	Δρmin = −0.13 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.016 (3)

Special details

Geometry. Mean plane data from final SHELXL refinement run:

Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane)

− 6.9207 (0.0045) x + 2.6720 (0.0070) y + 1.2907 (0.0258) z = 1.6311 (0.0280)

* 0.0009 (0.0017) C5 * 0.0040 (0.0017) C6 * −0.0049 (0.0020) C7 * 0.0008 (0.0020) C8 * 0.0041 (0.0020) C9 * −0.0049 (0.0019) C10

Rms deviation of fitted atoms = 0.0037

7.0968 (0.0044) x + 2.1883 (0.0076) y − 0.3198 (0.0290) z = 3.2426 (0.0273)

Angle to previous plane (with approximate e.s.d.) = 37.82 (0.06)

* −0.0128 (0.0014) N1 * 0.0036 (0.0014) N2 * 0.0169 (0.0015) C2 * −0.0138 (0.0015) C3 * 0.0062 (0.0015) C4

Rms deviation of fitted atoms = 0.0118

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.

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

	x	y	z	Uiso*/Ueq
C1	0.3006 (5)	0.6554 (4)	0.80572 (10)	0.0642 (8)
H1A	0.3405	0.5381	0.8165	0.096*
H1B	0.3926	0.7139	0.7822	0.096*
H1C	0.1924	0.6474	0.7818	0.096*
C2	0.2640 (4)	0.7595 (3)	0.86275 (9)	0.0442 (6)
C3	0.2065 (3)	0.9329 (3)	0.87092 (10)	0.0450 (6)
C4	0.2025 (3)	0.9646 (3)	0.93560 (10)	0.0405 (5)
C5	0.2472 (3)	0.7556 (3)	1.02564 (9)	0.0403 (5)
C6	0.1852 (3)	0.5886 (3)	1.04159 (11)	0.0473 (6)
H6	0.1477	0.5087	1.0116	0.057*
C7	0.1801 (4)	0.5423 (4)	1.10320 (11)	0.0580 (7)
H7	0.1403	0.4299	1.1146	0.070*
C8	0.2335 (4)	0.6613 (4)	1.14730 (12)	0.0653 (8)
H8	0.2286	0.6293	1.1884	0.078*
C9	0.2936 (4)	0.8261 (4)	1.13119 (11)	0.0607 (8)
H9	0.3289	0.9059	1.1615	0.073*
C10	0.3027 (3)	0.8759 (3)	1.06971 (11)	0.0492 (6)
H10	0.3452	0.9877	1.0586	0.059*
C11	0.1504 (4)	1.0539 (3)	0.82234 (12)	0.0619 (8)
C12	0.0708 (6)	1.2292 (4)	0.83890 (14)	0.0762 (10)
H12A	0.0403	1.2929	0.8022	0.114*
H12B	0.1568	1.2967	0.8622	0.114*
H12C	−0.0359	1.2110	0.8630	0.114*
O1	0.1666 (2)	1.1021 (2)	0.96597 (7)	0.0500 (5)
O2	0.1599 (5)	1.0093 (3)	0.76881 (9)	0.1074 (11)
O3	0.4281 (3)	0.3596 (2)	0.93939 (8)	0.0551 (5)
N1	0.2858 (3)	0.6831 (2)	0.91714 (8)	0.0431 (5)
N2	0.2520 (3)	0.8067 (2)	0.96254 (7)	0.0402 (4)
H1	0.337 (4)	0.566 (4)	0.9243 (13)	0.061 (8)*
H2	0.367 (5)	0.270 (5)	0.9496 (15)	0.085 (11)*
H3	0.490 (7)	0.369 (6)	0.9703 (19)	0.125 (17)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.084 (2)	0.0710 (16)	0.0375 (12)	−0.0125 (16)	0.0015 (14)	−0.0071 (11)
C2	0.0458 (12)	0.0538 (12)	0.0330 (11)	−0.0090 (11)	−0.0040 (11)	0.0038 (10)
C3	0.0448 (13)	0.0526 (12)	0.0375 (11)	−0.0109 (10)	−0.0043 (11)	0.0077 (9)
C4	0.0368 (12)	0.0463 (11)	0.0384 (11)	−0.0055 (9)	−0.0020 (11)	0.0046 (9)
C5	0.0319 (10)	0.0558 (12)	0.0330 (10)	0.0039 (10)	−0.0024 (10)	0.0044 (9)
C6	0.0410 (12)	0.0571 (12)	0.0438 (12)	0.0026 (11)	−0.0011 (11)	0.0087 (11)
C7	0.0520 (14)	0.0714 (16)	0.0506 (14)	0.0075 (13)	0.0062 (14)	0.0226 (12)
C8	0.0590 (16)	0.102 (2)	0.0354 (12)	0.0169 (17)	0.0014 (13)	0.0190 (14)
C9	0.0562 (17)	0.090 (2)	0.0358 (12)	0.0091 (15)	−0.0074 (13)	−0.0063 (12)
C10	0.0456 (13)	0.0632 (13)	0.0387 (12)	0.0011 (11)	−0.0026 (11)	−0.0016 (11)
C11	0.0751 (19)	0.0642 (16)	0.0463 (13)	−0.0182 (14)	−0.0160 (15)	0.0163 (11)
C12	0.097 (2)	0.0596 (15)	0.0717 (17)	−0.0058 (18)	−0.033 (2)	0.0198 (14)
O1	0.0555 (10)	0.0478 (8)	0.0469 (9)	0.0003 (8)	0.0034 (8)	0.0026 (7)
O2	0.180 (3)	0.1033 (16)	0.0388 (9)	0.009 (2)	−0.0126 (16)	0.0184 (10)
O3	0.0647 (11)	0.0487 (10)	0.0520 (10)	−0.0030 (9)	−0.0091 (10)	0.0012 (8)
N1	0.0476 (11)	0.0460 (10)	0.0356 (9)	0.0000 (9)	−0.0015 (9)	0.0004 (8)
N2	0.0449 (10)	0.0461 (9)	0.0298 (8)	−0.0011 (9)	0.0001 (8)	0.0010 (7)

Geometric parameters (Å, º)

C1—C2	1.495 (3)	C7—H7	0.9300
C1—H1A	0.9600	C8—C9	1.363 (4)
C1—H1B	0.9600	C8—H8	0.9300
C1—H1C	0.9600	C9—C10	1.394 (3)
C2—N1	1.328 (3)	C9—H9	0.9300
C2—C3	1.384 (3)	C10—H10	0.9300
C3—C4	1.431 (3)	C11—O2	1.217 (3)
C3—C11	1.458 (3)	C11—C12	1.489 (4)
C4—O1	1.256 (3)	C12—H12A	0.9600
C4—N2	1.376 (3)	C12—H12B	0.9600
C5—C6	1.382 (3)	C12—H12C	0.9600
C5—C10	1.383 (3)	O3—H2	0.84 (4)
C5—N2	1.430 (3)	O3—H3	0.82 (5)
C6—C7	1.389 (3)	N1—N2	1.381 (3)
C6—H6	0.9300	N1—H1	0.97 (3)
C7—C8	1.372 (4)
C2—C1—H1A	109.5	C9—C8—H8	119.8
C2—C1—H1B	109.5	C7—C8—H8	119.8
H1A—C1—H1B	109.5	C8—C9—C10	120.5 (3)
C2—C1—H1C	109.5	C8—C9—H9	119.7
H1A—C1—H1C	109.5	C10—C9—H9	119.7
H1B—C1—H1C	109.5	C5—C10—C9	118.6 (3)
N1—C2—C3	109.3 (2)	C5—C10—H10	120.7
N1—C2—C1	119.7 (2)	C9—C10—H10	120.7
C3—C2—C1	131.1 (2)	O2—C11—C3	120.6 (3)
C2—C3—C4	106.9 (2)	O2—C11—C12	120.0 (3)
C2—C3—C11	125.7 (2)	C3—C11—C12	119.3 (2)
C4—C3—C11	127.3 (2)	C11—C12—H12A	109.5
O1—C4—N2	122.8 (2)	C11—C12—H12B	109.5
O1—C4—C3	131.4 (2)	H12A—C12—H12B	109.5
N2—C4—C3	105.75 (19)	C11—C12—H12C	109.5
C6—C5—C10	121.2 (2)	H12A—C12—H12C	109.5
C6—C5—N2	119.66 (19)	H12B—C12—H12C	109.5
C10—C5—N2	119.1 (2)	H2—O3—H3	99 (3)
C5—C6—C7	118.7 (2)	C2—N1—N2	109.10 (18)
C5—C6—H6	120.6	C2—N1—H1	125.7 (17)
C7—C6—H6	120.6	N2—N1—H1	124.5 (17)
C8—C7—C6	120.5 (3)	C4—N2—N1	108.86 (17)
C8—C7—H7	119.8	C4—N2—C5	129.56 (18)
C6—C7—H7	119.8	N1—N2—C5	120.94 (17)
C9—C8—C7	120.4 (2)
N1—C2—C3—C4	3.0 (3)	C2—C3—C11—O2	−3.8 (5)
C1—C2—C3—C4	−177.3 (3)	C4—C3—C11—O2	−179.5 (3)
N1—C2—C3—C11	−173.4 (3)	C2—C3—C11—C12	172.6 (3)
C1—C2—C3—C11	6.3 (4)	C4—C3—C11—C12	−3.1 (4)
C2—C3—C4—O1	176.9 (2)	C3—C2—N1—N2	−3.0 (3)
C11—C3—C4—O1	−6.7 (5)	C1—C2—N1—N2	177.3 (2)
C2—C3—C4—N2	−1.9 (3)	O1—C4—N2—N1	−178.8 (2)
C11—C3—C4—N2	174.4 (2)	C3—C4—N2—N1	0.2 (3)
C10—C5—C6—C7	−0.3 (4)	O1—C4—N2—C5	10.5 (4)
N2—C5—C6—C7	−179.4 (2)	C3—C4—N2—C5	−170.5 (2)
C5—C6—C7—C8	0.8 (4)	C2—N1—N2—C4	1.7 (3)
C6—C7—C8—C9	−0.5 (4)	C2—N1—N2—C5	173.4 (2)
C7—C8—C9—C10	−0.3 (4)	C6—C5—N2—C4	136.8 (2)
C6—C5—C10—C9	−0.5 (4)	C10—C5—N2—C4	−42.3 (4)
N2—C5—C10—C9	178.6 (2)	C6—C5—N2—N1	−32.9 (3)
C8—C9—C10—C5	0.9 (4)	C10—C5—N2—N1	147.9 (2)