trans-Decahydro­naphthalene (deca­lin) from powder diffraction data

The title compound, C₁₀H₁₈, a deca­lin stereoisomer, crystallizes with Z' = 0.5 in the space group P2₁/n. The trans-deca­lin mol­ecule is located on an inversion centre with both rings in a chair conformation, making for a quasi-flat overall shape. Despite the absence of hydrogen bonds, it crystallizes easily. In this work the unknown crystal structure of trans-deca­lin has been solved and refined using X-ray powder diffraction data.

S1. Comment

Decahydronaphthalene, or decalin, is the hydrogen-saturated analogue of naphthalene. It has a wide range of applications in research and industry, from multi-purpose solvent, prospective use as a jet fuel for high-mach aircraft (Lai & Song, 1996) to a hydrogen-storage medium for fuel cells (Tsuji et al., 2007). As a solvent it is typically used for index matching in optical studies of polymers or colloids due to its high refractive index of n = 1.47. Its two isomers, cis and trans (Fig. 3), have different thermodynamic properties (Lal & Swinton, 1969), which makes it a system of choice for studies of the effect of stereoisomerism on physical properties in liquids.

In the field of glass physics the influence of the isomers on the behaviour of decalin recently caused interest. The fragility, a property quantifying the `rapidity' of solidification as a function of temperature at the glass transition point, of decalin has been investigated. It was found to have one of the highest fragility values for molecular liquids at a mixing ratio of 1:1, while the fragility of cis-decalin was found to be moderate (Wang et al., 2002; Duvvuri & Richert, 2002). This would imply dependence of the fragility on isomeric composition, which is unusual in this domain and so prompted research on the microscopic origin of the effect (Dalle-Ferrier et al., 2007). The study of anharmonicity of vibrational modes in solidified cis-decalin investigated that microscopic origin (Plazanet & Schober, 2008) and also led to this work.

The two known isomers are distinct in their conformational freedom. trans-Decalin, (I), is rigid and confined to one conformation with a centre of symmetry at the centre of mass, whereas cis-decalin by contrast can interchange between several conformations, with two chiral chair–chair ground states (Gerig & Roberts, 1966). Experiments on a differential scanning calorimeter with high cooling rate show a very pronounced exothermic signal on crystallization of trans-decalin with no further features appearing down to liquid nitrogen temperature. Observations made during experiments that involved cooling past the melting temperature confirm this finding in showing quick crystallization and a crystal structure that is stable and independent of cooling history.

As the crystallization of trans-decalin (Fig. 1) happens very quickly it is hard to bypass. In the course of experiments, attempts have been made to vitrify trans-decalin by quenching it in liquid nitrogen. Quantities as small as a few milligrams quenched from room temperature in aluminium containers did not show any signature of amorphicity during further investigation. In the course of crystal structure determination of trans-decalin difficulties arose from the quick crystallization behaviour. Measurements of an in situ crystallized sample on the high-resolution X-ray powder diffractometer ID31 at ESRF (Fitch, 2004) showed very narrow peaks and suggested large grain sizes. Although the sample was spun for angular averaging during data acquisition the grain sizes were reckoned to be too big for accurate sampling of peak intensities. Hence a further investigation of the crystallization behaviour was conducted on the X-ray diffractometer SNBL BM01 on a bending magnet at ESRF, which operates a two-dimensional mar345 detector. The two-dimensional pattern showed strongly inhomogeneous angular intensity distribution and so proved the intensities first collected on ID31 to be insufficient for accurate refinement. During further treatment the one-dimensional pattern was used to determine cell parameters, while the integrated two-dimensional pattern was used for intensity-sensitive evaluation and structure solution.

The molecules of (I) are located on crystallographic centres of inversion. Both rings have the chair conformation. The packing of the molecules in the unit cell is shown in Fig. 4.

Related literature

For related literature, see: Boultif & Louër (2004); Coelho (2000); Dalle-Ferrier, Thibierge, Alba-Simionesco, Berthier, Biroli, Bouchaud, Ladieu, L'Hôte & Tarjus (2007); David et al. (2006); Delley (1990); Duvvuri & Richert (2002); Fitch (2004); Gerig & Roberts (1966); Hammersley et al. (1996); Lai & Song (1996); Lal & Swinton (1969); Plazanet & Schober (2008); Rietveld (1969); Tsuji et al. (2007); Wang et al. (2002).

S2. Experimental

trans-Decalin was purchased from Sigma Aldrich with a purity higher than 99% and used without further treatment. For both measurements glass capillaries with a diameter of 1 mm for ID31 and 0.5 mm for SNBL BM01A were used as sample containers. The sample was mounted on the instruments at room temperature, where it is liquid, and then cooled down to 100 K using a cryostream cold N₂ gas blower. An in situ phase change from liquid to crystalline powder could thus be achieved. The measurement on ID31 was performed at a wavelength of 0.79984 (4) Å; for the SNBL BM01A measurement the wavelength used was 0.694 (1) Å.

S3. Refinement

The high-resolution powder diffraction pattern from ID31 was indexed using the program DICVOL (Boultif & Louër, 2004), implemented in the program package DASH (David et al., 2006) via the positions of 25 diffraction peaks. Systematic absences suggested space group P2₁/n. The resulting unit cell holds two molecules situated on centres of symmetry with half a molecule as an asymmetric unit. A molecular structure of trans-decalin was optimized using the ab initio code DMol3 (Delley, 1990), then converted into z-matrix format and its centre fixed on the centre of symmetry (0,0,0) of the cell. Data from SNBL BM01A was reduced using the Fit2D (Hammersley et al., 1996) package. With the simulated annealing feature of the program TOPAS (Coelho, 2000) the three degrees of freedom corresponding to the orientations of the molecule were optimized to obtain the best agreement with the two-dimensional data from SNBL BM01A. The solved structure was refined using TOPAS with H atoms fixed at a distance of 0.96 Å from C atoms. In the refinement (Rietveld, 1969) (Fig. 2) a total of four parameters, three orientational degrees of freedom and B_overall, were fitted to reflections contributing to the profile. Peak shapes were modelled using a Thompson–Cox–Hastings function and residual preferred orientation was described by spherical harmonics of order four. Standard uncertainties were calculated by the bootstrap method implemented in TOPAS.

Computing details

Data collection: ESRF: ID31 and BM01A (name of software?); cell refinement: DASH (David et al., 2006); data reduction: Fit2D (Hammersley et al., 1996); program(s) used to solve structure: TOPAS (Coelho, 2000); program(s) used to refine structure: TOPAS (Coelho, 2000); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2009).

Figures

	Fig. 1. Structure of the trans-decalin molecule. Symmetry code i = -x, -y, -z.
	Fig. 2. Final Rietveld refinement: Observed, calculated and difference profiles for trans-decalin.
	Fig. 3. Decalin exists in a cis (1) or trans (2) isomer, with the relative position of the H atoms to the two common C atoms as a distinction criterion. The ground state of trans-decalin is not chirally split as it is for cis-decalin.
	Fig. 4. Packing diagram of crystalline trans-decalin viewed along the c axis.

trans-Decahydronaphthalene

Crystal data

C10H18	Dx = 1.067 Mg m^−3
Mr = 138.25	Melting point: 242 K
Monoclinic, P21/n	Synchrotron radiation, λ = 0.694(1) Å
a = 7.8101 (5) Å	µ = 0.03 mm^−1
b = 10.4690 (12) Å	T = 100 K
c = 5.2638 (3) Å	Particle morphology: plate-like
β = 90.990 (7)°	colourless
V = 430.33 (6) Å^3	cylinder, 10 × 0.5 mm
Z = 2	Specimen preparation: Prepared at 293 K and 100 kPa

Data collection

SNBL diffractometer	Data collection mode: transmission
Radiation source: ESRF Synchrotron	Scan method: continuous
None monochromator	2θmin = 2°, 2θmax = 28.5°, 2θstep = 0.02°
Specimen mounting: in situ crystallised liquid in capillary

Refinement

Rp = ?	Profile function: Thompson-Cox-Hastings (Thompson et al., 1987)
Rwp = 0.093	4 parameters
Rexp = ?	H atoms treated by a mixture of independent and constrained refinement
RBragg = 0.039
χ^2 = ?	Background function: square polynomial
? data points	Preferred orientation correction: sph. harm. of order four (Järvinen, 1993)
Excluded region(s): none

Special details

Experimental. Please find the TOPAS input file for structure refinement and the experimental data in the given supplementary information.

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell esds are taken into account in the estimation of distances, angles and torsion angles

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

	x	y	z	Uiso*/Ueq
C1	0.0821 (4)	0.1533 (3)	0.1730 (11)	0.40 (17)
C2	−0.0156 (2)	0.0269 (3)	0.1338 (2)	0.395025
C4	0.2085 (3)	−0.0442 (5)	−0.1779 (9)	0.395025
C5	0.3055 (3)	0.0819 (6)	−0.1382 (10)	0.395025
C6	0.2744 (4)	0.1358 (4)	0.1283 (11)	0.395025
H3	0.0374 (6)	0.21675 (12)	0.0582 (16)	0.395025
H4	0.0651 (7)	0.1845 (7)	0.3422 (14)	0.395025
H5	0.0276 (4)	−0.0335 (5)	0.2562 (3)	0.395025
H7	0.2537 (3)	−0.1075 (4)	−0.0631 (14)	0.395025
H8	0.2267 (6)	−0.0749 (8)	−0.3471 (12)	0.395025
H9	0.4259 (4)	0.0687 (7)	−0.1615 (14)	0.395025
H10	0.2682 (6)	0.1429 (7)	−0.2636 (11)	0.395025
H11	0.3216 (4)	0.0786 (6)	0.2537 (10)	0.395025
H12	0.3326 (6)	0.2160 (5)	0.1487 (16)	0.395025

Geometric parameters (Å, º)

C1—C2	1.540 (4)	C2—H5	0.960 (4)
C1—C6	1.535 (5)	C4—H7	0.960 (7)
C2—C2^i	1.540 (2)	C4—H8	0.960 (8)
C2—C4^i	1.539 (3)	C5—H9	0.960 (4)
C4—C5	1.535 (7)	C5—H10	0.960 (9)
C5—C6	1.535 (8)	C6—H11	0.960 (7)
C1—H3	0.960 (7)	C6—H12	0.960 (7)
C1—H4	0.960 (9)
C5···H9^ii	3.043 (7)	H7···H3^i	2.546 (5)
H3···H5^i	2.578 (7)	H8···H4^i	2.552 (8)
H3···H7^i	2.546 (5)	H9···C5^ii	3.043 (7)
H4···H8^i	2.552 (8)	H9···H9^ii	2.496 (9)
H5···H7	2.578 (6)	H9···H11^ii	2.557 (7)
H5···H11	2.579 (5)	H10···H5^i	2.579 (6)
H5···H3^i	2.578 (7)	H11···H5	2.579 (5)
H5···H10^i	2.579 (6)	H11···H9^ii	2.557 (7)
H7···H5	2.578 (6)
C2—C1—C6	111.2 (3)	C5—C4—H7	109.4 (4)
C1—C2—C2^i	110.6 (3)	C5—C4—H8	109.5 (6)
C1—C2—C4^i	111.3 (3)	H7—C4—H8	107.1 (7)
C2^i—C2—C4^i	110.6 (2)	C2^i—C4—H7	109.7 (4)
C2^i—C4—C5	111.1 (3)	C2^i—C4—H8	109.9 (4)
C4—C5—C6	110.8 (4)	C4—C5—H9	109.9 (7)
C1—C6—C5	110.8 (4)	C4—C5—H10	109.6 (5)
C2—C1—H3	109.7 (4)	C6—C5—H9	109.9 (6)
C2—C1—H4	109.9 (5)	C6—C5—H10	109.4 (6)
C6—C1—H3	109.4 (5)	H9—C5—H10	107.1 (7)
C6—C1—H4	109.5 (5)	C1—C6—H11	109.5 (5)
H3—C1—H4	107.1 (7)	C1—C6—H12	109.9 (5)
C1—C2—H5	108.0 (3)	C5—C6—H11	109.5 (5)
C2^i—C2—H5	108.3 (3)	C5—C6—H12	110.0 (7)
C4^i—C2—H5	108.1 (3)	H11—C6—H12	107.1 (7)
C6—C1—C2—C2^i	−56.6 (4)	C4^i—C2—C2^i—C4	180.0 (3)
C6—C1—C2—C4^i	−179.9 (4)	C1—C2—C4^i—C5^i	179.9 (4)
C2—C1—C6—C5	56.6 (5)	C2^i—C4—C5—C6	56.6 (4)
C1—C2—C2^i—C4	56.3 (3)	C4—C5—C6—C1	−56.4 (5)
C1—C2—C2^i—C1^i	180.0 (2)

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