3,5-Diacetyl­heptane-2,6-dione

The title compound, C₁₁H₁₆O₄, was produced when pentane-2,4-dione (acacH) was treated with formaldehyde in a ca 2.16:1 molar ratio. The compound exists in the solid state as the keto tautomer, although the enol tautomer also exists in solution. The C=O distances are in the range 1.2097 (18)–1.2169 (18) Å. Inter­molecular C=O...C=O inter­actions exist, the shortest having a C...O distance of 3.378 (2) Å.

Key indicators

• Single-crystal X-ray study
• T = 100 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.041
• wR factor = 0.113
• Data-to-parameter ratio = 18.9

checkCIF/PLATON results

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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           33.70
           From the CIF: _reflns_number_total               2647
           Count of symmetry unique reflns         2661
           Completeness (_total/calc)             99.47%
           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

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

   0 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
   0 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

The title compound, (I), was first explored by Scholtz (1897) and Knoevenagel et al. (1903). Our goal was to utilize the title compound (I) in the preparation of polynuclear metal complexes.

Solutions of (I) in CHCl₃ show evidence in ¹H NMR spectra for both keto and enol tautomers, but the crystal contains only the keto form. C3 and C9 (Fig. 1) are protonated and tetrahedral, all the C—C bond lengths to them are typical of single bonds, and the four C═O distances (Table 1) are typical of double bonds.

Allen et al. (1998) have shown that intermolecular carbonyl···carbonyl interactions in ketones can significantly influence the packing of such molecules, and have identified three major geometric types. The shortest such contact in (I), O3···C10 (1 - x, y - 1/2, 3/2 - z) resembles their perpendicular interaction, and its O···C distance 3.387 (2) Å is near the mean distance they report. However, the O atom in this interaction is actually nearer the methyl C [O3···C11 = 3.267 (2) Å].

Related literature

The title compound was described over 100 years ago (Scholtz, 1897; Knoevenagel et al., 1903). We have recently reported the structure of 1,1',1"-[(5R,6R)-6-hydroxy-6-methyl-tetrahydro-2H-pyran-3,\ 3,5-triyl]triethanone (Burton et al., 2007), which is formed when excess formaldehyde is used in the synthesis.

For related literature, see: Allen et al. (1998); Wilson (1963).

S2. Experimental

In accordance with previously described preparative methods (Knoevenagel et al., 1903; Wilson, 1963), a mixture of 40 ml acetylacetone (0.39 mol) and 13.5 ml of formaldehyde (37% aqueous solution; 0.18 mol) was stirred for 5 days. The product separated on standing into a gold-colored organic bottom layer (40 ml) and a pale-yellow aqueous top layer (10 ml). The organic layer was dried over MgSO₄ and an equal volume of diethyl ether was added. The resulting solution was cooled in a dry ice-acetone bath to produce a white solid. After repeatedly taking up the viscous portions in a minimum of diethyl ether and cooling in the dry ice-acetone bath, a total of 11.0 g (0.052 mole, 26% yield) of crystalline solid, mp 39.5–41.0 °C, was isolated. X-ray quality crystals were obtained by cooling a solution in diethyl ether in a dry ice-acetone bath.

S3. Refinement

H atoms were placed in idealized positions with C—H distances 0.98 - 1.00 Å and thereafter treated as riding. U_iso for H was assigned as 1.2 times U_eq of the attached C atoms (1.5 for methyl). A torsional parameter was refined for each methyl group. The absolute structure could not be determined, and Friedel pairs were averaged.

Computing details

Data collection: COLLECT (Nonius, 2000); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997) and SCALEPACK; program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. Numbering scheme and ellipsoids at the 50% level. H atoms are represented with arbitrary radius.

3,5-Diacetylheptane-2,6-dione

Crystal data

C11H16O4	Dx = 1.203 Mg m^−3
Mr = 212.24	Melting point = 313.5–314.0 K
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 2556 reflections
a = 7.810 (2) Å	θ = 2.5–33.7°
b = 8.611 (2) Å	µ = 0.09 mm^−1
c = 17.431 (4) Å	T = 100 K
V = 1172.3 (5) Å^3	Fragment, colourless
Z = 4	0.47 × 0.43 × 0.40 mm
F(000) = 456

Data collection

Nonius KappaCCD (with Oxford Cryostream) diffractometer	2352 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.016
Graphite monochromator	θmax = 33.7°, θmin = 2.8°
ω scans with κ offsets	h = −11→11
15692 measured reflections	k = −13→13
2647 independent reflections	l = −27→27

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.041	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.113	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0668P)^2 + 0.1309P] where P = (Fo^2 + 2Fc^2)/3
2647 reflections	(Δ/σ)max = 0.006
140 parameters	Δρmax = 0.29 e Å^−3
0 restraints	Δρmin = −0.18 e Å^−3

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	0.05730 (14)	0.48942 (13)	0.67423 (5)	0.0284 (2)
O2	−0.06423 (14)	0.21860 (16)	0.54715 (7)	0.0388 (3)
O3	0.52584 (15)	0.07629 (14)	0.65558 (6)	0.0346 (3)
O4	0.45874 (17)	0.10347 (15)	0.84527 (6)	0.0383 (3)
C1	0.1592 (2)	0.53906 (18)	0.54771 (8)	0.0296 (3)
H1A	0.0884	0.6328	0.5508	0.044*
H1B	0.1286	0.4802	0.5016	0.044*
H1C	0.2803	0.5686	0.5452	0.044*
C2	0.12923 (16)	0.44037 (15)	0.61741 (7)	0.0212 (2)
C3	0.19679 (15)	0.27436 (14)	0.61312 (6)	0.0184 (2)
H3	0.3141	0.2768	0.5901	0.022*
C4	0.08071 (18)	0.17786 (17)	0.56105 (7)	0.0246 (2)
C5	0.1554 (2)	0.03050 (19)	0.52954 (9)	0.0366 (3)
H5A	0.0644	−0.0469	0.5234	0.055*
H5B	0.2423	−0.0092	0.5650	0.055*
H5C	0.2082	0.0514	0.4796	0.055*
C6	0.20811 (15)	0.19736 (15)	0.69250 (6)	0.0195 (2)
H6A	0.1052	0.2245	0.7228	0.023*
H6B	0.2105	0.0831	0.6863	0.023*
C7	0.69870 (18)	0.2565 (2)	0.72430 (11)	0.0348 (3)
H7A	0.7860	0.1755	0.7298	0.052*
H7B	0.6838	0.3103	0.7734	0.052*
H7C	0.7351	0.3310	0.6851	0.052*
C8	0.53220 (16)	0.18388 (16)	0.70076 (7)	0.0231 (2)
C9	0.36884 (15)	0.24996 (14)	0.73593 (6)	0.0182 (2)
H9	0.3751	0.3659	0.7337	0.022*
C10	0.36087 (17)	0.20085 (16)	0.82022 (7)	0.0236 (2)
C11	0.22526 (19)	0.27536 (18)	0.86857 (7)	0.0294 (3)
H11A	0.2417	0.2456	0.9223	0.044*
H11B	0.1122	0.2407	0.8512	0.044*
H11C	0.2332	0.3885	0.8638	0.044*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0318 (5)	0.0291 (5)	0.0243 (4)	0.0065 (4)	0.0051 (4)	−0.0015 (4)
O2	0.0300 (5)	0.0493 (7)	0.0371 (6)	0.0006 (5)	−0.0138 (5)	−0.0062 (5)
O3	0.0336 (5)	0.0348 (6)	0.0354 (5)	0.0123 (5)	−0.0005 (4)	−0.0080 (5)
O4	0.0445 (7)	0.0436 (6)	0.0269 (5)	0.0058 (6)	−0.0062 (5)	0.0120 (4)
C1	0.0315 (6)	0.0299 (6)	0.0275 (6)	0.0059 (5)	0.0050 (5)	0.0104 (5)
C2	0.0197 (5)	0.0237 (5)	0.0201 (4)	0.0015 (4)	−0.0005 (4)	0.0018 (4)
C3	0.0182 (5)	0.0219 (5)	0.0152 (4)	0.0000 (4)	−0.0008 (4)	−0.0002 (4)
C4	0.0287 (6)	0.0280 (6)	0.0169 (4)	−0.0038 (5)	−0.0027 (4)	−0.0007 (4)
C5	0.0404 (8)	0.0341 (7)	0.0353 (7)	−0.0033 (7)	−0.0031 (6)	−0.0142 (6)
C6	0.0203 (5)	0.0220 (5)	0.0163 (4)	−0.0024 (4)	−0.0024 (4)	0.0018 (4)
C7	0.0203 (6)	0.0335 (7)	0.0506 (9)	−0.0010 (6)	−0.0019 (6)	0.0075 (7)
C8	0.0211 (5)	0.0231 (5)	0.0250 (5)	0.0033 (5)	−0.0009 (4)	0.0053 (4)
C9	0.0197 (4)	0.0184 (4)	0.0165 (4)	−0.0011 (4)	−0.0014 (4)	0.0012 (4)
C10	0.0283 (6)	0.0249 (5)	0.0175 (4)	−0.0066 (5)	−0.0043 (4)	0.0018 (4)
C11	0.0338 (7)	0.0348 (7)	0.0198 (5)	−0.0117 (6)	0.0050 (5)	−0.0036 (5)

Geometric parameters (Å, º)

O1—C2	1.2145 (15)	C5—H5C	0.9800
O2—C4	1.2097 (18)	C6—C9	1.5343 (16)
O3—C8	1.2169 (18)	C6—H6A	0.9900
O4—C10	1.2158 (17)	C6—H6B	0.9900
C1—C2	1.5011 (18)	C7—C8	1.500 (2)
C1—H1A	0.9800	C7—H7A	0.9800
C1—H1B	0.9800	C7—H7B	0.9800
C1—H1C	0.9800	C7—H7C	0.9800
C2—C3	1.5256 (17)	C8—C9	1.5256 (18)
C3—C4	1.5284 (17)	C9—C10	1.5301 (17)
C3—C6	1.5370 (16)	C9—H9	1.0000
C3—H3	1.0000	C10—C11	1.498 (2)
C4—C5	1.501 (2)	C11—H11A	0.9800
C5—H5A	0.9800	C11—H11B	0.9800
C5—H5B	0.9800	C11—H11C	0.9800
C2—C1—H1A	109.5	C9—C6—H6B	109.4
C2—C1—H1B	109.5	C3—C6—H6B	109.4
H1A—C1—H1B	109.5	H6A—C6—H6B	108.0
C2—C1—H1C	109.5	C8—C7—H7A	109.5
H1A—C1—H1C	109.5	C8—C7—H7B	109.5
H1B—C1—H1C	109.5	H7A—C7—H7B	109.5
O1—C2—C1	122.37 (12)	C8—C7—H7C	109.5
O1—C2—C3	121.72 (11)	H7A—C7—H7C	109.5
C1—C2—C3	115.90 (10)	H7B—C7—H7C	109.5
C2—C3—C4	109.48 (10)	O3—C8—C7	121.98 (13)
C2—C3—C6	112.33 (10)	O3—C8—C9	120.65 (12)
C4—C3—C6	109.52 (10)	C7—C8—C9	117.37 (12)
C2—C3—H3	108.5	C8—C9—C10	108.47 (10)
C4—C3—H3	108.5	C8—C9—C6	112.08 (10)
C6—C3—H3	108.5	C10—C9—C6	111.04 (10)
O2—C4—C5	122.38 (14)	C8—C9—H9	108.4
O2—C4—C3	121.09 (13)	C10—C9—H9	108.4
C5—C4—C3	116.53 (12)	C6—C9—H9	108.4
C4—C5—H5A	109.5	O4—C10—C11	122.55 (12)
C4—C5—H5B	109.5	O4—C10—C9	120.66 (12)
H5A—C5—H5B	109.5	C11—C10—C9	116.78 (11)
C4—C5—H5C	109.5	C10—C11—H11A	109.5
H5A—C5—H5C	109.5	C10—C11—H11B	109.5
H5B—C5—H5C	109.5	H11A—C11—H11B	109.5
C9—C6—C3	111.34 (9)	C10—C11—H11C	109.5
C9—C6—H6A	109.4	H11A—C11—H11C	109.5
C3—C6—H6A	109.4	H11B—C11—H11C	109.5
O1—C2—C3—C4	106.19 (14)	O3—C8—C9—C10	107.67 (13)
C1—C2—C3—C4	−74.56 (13)	C7—C8—C9—C10	−72.17 (14)
O1—C2—C3—C6	−15.71 (16)	O3—C8—C9—C6	−15.27 (16)
C1—C2—C3—C6	163.54 (11)	C7—C8—C9—C6	164.88 (12)
C2—C3—C4—O2	−20.20 (17)	C3—C6—C9—C8	−70.39 (13)
C6—C3—C4—O2	103.37 (14)	C3—C6—C9—C10	168.12 (10)
C2—C3—C4—C5	160.62 (12)	C8—C9—C10—O4	−11.25 (17)
C6—C3—C4—C5	−75.80 (14)	C6—C9—C10—O4	112.32 (14)
C2—C3—C6—C9	−79.56 (12)	C8—C9—C10—C11	170.22 (11)
C4—C3—C6—C9	158.56 (10)	C6—C9—C10—C11	−66.21 (14)