Redetermination of 9,10-dimethyl­anthracene

The crystal structure of the title compound, C₁₆H₁₄, was refined by Iball & Low [Acta Cryst. (1974). B30, 2203-2205] to an R value of 0.080. The present redetermination confirms the previous study but with improved precision and with all H atoms located and refined. The atoms of the methyl group are disordered over two sites with occupancies 0.55 (3) and 0.45 (3). The mol­ecular symmetry is C_i. The crystal structure is stabilized by van der Waals inter­actions.

Key indicators

• Single-crystal X-ray study
• T = 290 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.045
• wR factor = 0.137
• Data-to-parameter ratio = 10.8

checkCIF/PLATON results

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Alert level C
PLAT390_ALERT_3_C Deviating Methyl C8      X-C-H Bond Angle ......     117.00 Deg.

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   1 ALERT level C = Check and explain
   0 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
   1 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   0 ALERT type 5 Informative message, check

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S1. Comment

In the literature, there is a single paper related to the crystal structure of 9,10-dimethylanthracene (I) [Iball & Low, 1974; CSD refcode DMANTR (Cambridge Structural Database, Version 5.28; Allen, 2002)]. In that determination, a reliability factor was R=0.080 for 712 data, and hydrogen atom coordinates were included in calculated positions without any refinement. However, the redetermination of (I) from recollected intensity data is presented here. The disorder of methyl group was detected over two sites (Fig. 1) with site occupancy factors 0.55 (3) and 0.45 (3). Apart from this disorder and the higher precision of the geometric parameters [σ(C—C) = 0.002–0.003 Å in the present work, compared with 0.009–0.012 Å in the earlier work (Iball & Low, 1974)], the results obtained agree well with the already published data. In the crystal structure of (I) the asymmetric unit consists of a half-molecule whereas the other half is generated by a centre of inversion. The molecule is planar with the largest r.m.s. deviation from the best least-square plane being 0.005 (1) Å for C5. The crystal packing is stabilized by van der Waals interactions (Fig. 2).

Related literature

For the previous structure determination, see: Iball & Low (1974) [refcode DMANTR, Cambridge Structural Database, Version 5.28; Allen, 2002)].

S2. Experimental

The crystals of (I) were obtained from the vapour in a specially constructed glass apparatus consisting of the two main parts, namely a cold copper plate used as a substrate and an electrically heated molybdenic boat, both equipped with the Fe/constantan thermocouples which allowed an independent control of the T₁ and T₂ temperatures of these parts, respectively. Under a low background pressure of 10^-3 mbar, the crystals were nucleated at 311 K/330 K (T₁/T₂) and grown at 318 K /330 K.

S3. Refinement

All C-bound H atoms, except those on C8 atom were included in the refinement at the geometrically calculated positions and refined using a riding model with C—H distances of 0.93 Å and with U_iso(H)=1.2U_eq(C). The H atoms of methyl group were located in a difference Fourier map and refined with U_iso(H)=1.5U_eq(C). These atoms were found to be disordered over two sites with refined occupancies of 0.55 (3): 0.45 (3).

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2007); cell refinement: CrysAlis RED (Oxford Diffraction, 2007); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003) and DIAMOND (Brandenburg, 2006); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. View of molecule of (I) showing the atom-numbering scheme and disordered H atoms of methyl group. Displacement ellipsoids are drawn at the 20% probability level and H atoms are shown as small spheres of arbitrary radii. Symetry code (a): 1 - x, -y, 1 - z.
	Fig. 2. The crystal packing, viewed along the a axis.

9,10-dimethylanthracene

Crystal data

C16H14	F(000) = 220
Mr = 206.27	Dx = 1.228 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3013 reflections
a = 7.8229 (6) Å	θ = 2.6–25.4°
b = 5.3093 (4) Å	µ = 0.07 mm^−1
c = 13.4649 (10) Å	T = 290 K
β = 93.861 (7)°	Columnar, yellow
V = 557.98 (7) Å^3	0.50 × 0.16 × 0.04 mm
Z = 2

Data collection

Oxford Diffraction Xcalibur3 CCD diffractometer	1003 independent reflections
Radiation source: fine-focus sealed tube	692 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.020
ω scans	θmax = 25.4°, θmin = 2.6°
Absorption correction: analytical (CrysAlis RED; Oxford Diffraction, 2007)	h = −9→9
Tmin = 0.947, Tmax = 0.994	k = −3→6
3013 measured reflections	l = −16→16

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)] = 0.046	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.137	w = 1/[σ^2(Fo^2) + (0.0784P)^2 + 0.0148P] where P = (Fo^2 + 2Fc^2)/3
S = 1.11	(Δ/σ)max < 0.001
1003 reflections	Δρmax = 0.17 e Å^−3
93 parameters	Δρmin = −0.17 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: 0.13 (2)

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	Occ. (<1)
C1	0.1584 (2)	0.1546 (3)	0.30410 (13)	0.0641 (5)
H1	0.0550	0.1503	0.2657	0.077*
C2	0.1862 (2)	−0.0076 (3)	0.38108 (13)	0.0571 (5)
H2	0.1008	−0.1222	0.3944	0.069*
C3	0.34228 (18)	−0.0089 (2)	0.44254 (10)	0.0464 (5)
C4	0.62951 (19)	0.1785 (2)	0.47711 (11)	0.0468 (5)
C5	0.47336 (19)	0.1693 (2)	0.41972 (10)	0.0464 (5)
C6	0.4366 (2)	0.3365 (3)	0.33742 (12)	0.0580 (5)
H6	0.5191	0.4533	0.3216	0.070*
C7	0.2856 (2)	0.3297 (3)	0.28208 (13)	0.0649 (6)
H7	0.2658	0.4412	0.2293	0.078*
C8	0.7676 (3)	0.3651 (4)	0.45414 (18)	0.0626 (6)
H8A	0.798 (6)	0.474 (9)	0.514 (4)	0.094*	0.55 (3)
H8B	0.732 (7)	0.460 (10)	0.402 (4)	0.094*	0.55 (3)
H8C	0.871 (7)	0.268 (9)	0.440 (4)	0.094*	0.55 (3)
H8D	0.801 (8)	0.352 (10)	0.379 (5)	0.094*	0.45 (3)
H8E	0.876 (9)	0.355 (11)	0.495 (4)	0.094*	0.45 (3)
H8F	0.732 (8)	0.540 (11)	0.449 (5)	0.094*	0.45 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0578 (11)	0.0703 (11)	0.0630 (11)	0.0084 (9)	−0.0039 (9)	−0.0041 (9)
C2	0.0506 (9)	0.0576 (10)	0.0629 (10)	−0.0015 (7)	0.0020 (8)	−0.0076 (8)
C3	0.0471 (9)	0.0439 (8)	0.0487 (9)	0.0016 (6)	0.0077 (7)	−0.0091 (6)
C4	0.0459 (9)	0.0446 (8)	0.0511 (9)	−0.0023 (6)	0.0116 (7)	−0.0077 (6)
C5	0.0507 (9)	0.0422 (8)	0.0476 (8)	0.0021 (6)	0.0126 (7)	−0.0057 (6)
C6	0.0615 (11)	0.0539 (10)	0.0596 (10)	0.0013 (7)	0.0109 (8)	0.0031 (7)
C7	0.0689 (12)	0.0666 (11)	0.0592 (10)	0.0119 (9)	0.0048 (9)	0.0048 (8)
C8	0.0575 (11)	0.0609 (11)	0.0699 (13)	−0.0118 (9)	0.0093 (10)	0.0028 (10)

Geometric parameters (Å, º)

C1—C2	1.354 (2)	C6—C7	1.355 (2)
C1—C7	1.408 (3)	C6—H6	0.9300
C1—H1	0.9300	C7—H7	0.9300
C2—C3	1.428 (2)	C8—H8A	1.00 (5)
C2—H2	0.9300	C8—H8B	0.90 (5)
C3—C4^i	1.414 (2)	C8—H8C	0.99 (5)
C3—C5	1.443 (2)	C8—H8D	1.07 (6)
C4—C5	1.402 (2)	C8—H8E	0.98 (6)
C4—C8	1.513 (2)	C8—H8F	0.97 (6)
C5—C6	1.434 (2)
C2—C1—C7	120.1 (2)	C4—C8—H8A	110 (2)
C2—C1—H1	119.9	C4—C8—H8B	110 (3)
C7—C1—H1	119.9	H8A—C8—H8B	110 (4)
C1—C2—C3	122.3 (2)	C4—C8—H8C	108 (3)
C1—C2—H2	118.9	H8A—C8—H8C	108 (4)
C3—C2—H2	118.9	H8B—C8—H8C	111 (4)
C4^i—C3—C2	122.0 (1)	C4—C8—H8D	112 (3)
C4^i—C3—C5	120.3 (1)	H8A—C8—H8D	137 (4)
C2—C3—C5	117.7 (1)	H8B—C8—H8D	51 (3)
C5—C4—C3^i	119.0 (1)	H8C—C8—H8D	62 (3)
C5—C4—C8	121.2 (2)	C4—C8—H8E	117 (3)
C3^i—C4—C8	119.8 (2)	H8A—C8—H8E	55 (3)
C4—C5—C6	121.7 (1)	H8B—C8—H8E	133 (4)
C4—C5—C3	120.7 (1)	H8C—C8—H8E	53 (3)
C6—C5—C3	117.5 (2)	H8D—C8—H8E	106 (4)
C7—C6—C5	122.0 (2)	C4—C8—H8F	116 (3)
C7—C6—H6	119.0	H8A—C8—H8F	63 (3)
C5—C6—H6	119.0	H8B—C8—H8F	48 (4)
C6—C7—C1	120.3 (2)	H8C—C8—H8F	136 (4)
C6—C7—H7	119.8	H8D—C8—H8F	95 (4)
C1—C7—H7	119.8	H8E—C8—H8F	109 (4)
C7—C1—C2—C3	0.1 (2)	C2—C3—C5—C4	179.9 (1)
C1—C2—C3—C4^i	179.9 (1)	C4^i—C3—C5—C6	−179.9 (1)
C1—C2—C3—C5	−0.5 (2)	C2—C3—C5—C6	0.6 (2)
C3^i—C4—C5—C6	179.8 (1)	C4—C5—C6—C7	−179.6 (1)
C8—C4—C5—C6	−0.5 (2)	C3—C5—C6—C7	−0.2 (2)
C3^i—C4—C5—C3	0.5 (2)	C5—C6—C7—C1	−0.2 (3)
C8—C4—C5—C3	−179.8 (2)	C2—C1—C7—C6	0.2 (3)
C4^i—C3—C5—C4	−0.5 (2)

Symmetry code: (i) −x+1, −y, −z+1.