Icosane-1,20-di­thiol

In the molecular structure of the title compound, C₂₀H₄₂S₂, (I), the skeleton of the hydro­carbon has an all-trans conformation. The terminal S-H bond is in a gauche conformation with respect to the skeleton. In the crystal structure, the mol­ecules are arranged along the c axis, the longest axis, forming layers in which the long axis of the mol­ecule is inclined to the layer plane. This packing is very similar to that of the smectic C structure of liquid crystals. Except for the length of the c axis, no big difference was observed between the crystal data obtained here and those of homologues with even numbers of C atoms already reported.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.057
• wR factor = 0.159
• Data-to-parameter ratio = 19.1

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level A:



ABSTM_02  Alert A Test not performed as the _exptl_absorpt_correction_type
          has not been identified. See test ABSTY_01.

ABSTY_01  Alert A The absorption correction should be one of the following
          *  none
          *  analytical
          *  integration
          *  numerical
          *  gaussian
          *  empirical
          *  psi-scan
          *  multi-scan
          *  refdelf
          *  sphere
          *  cylinder


 Alert Level C:



PLAT_420  Alert C D-H Without Acceptor       S(1)   -   H(1S)             ?


 2 Alert Level A = Potentially serious problem

 0 Alert Level B = Potential problem

 1 Alert Level C = Please check

---

Computing details

Data collection: MSC/AFC Diffractometer Control Software (Molecular Structure Corporation, 1992); cell refinement: MSC/AFC Diffractometer Control Software; data reduction: TEXSAN (Molecular Structure Corporation, 2000); program(s) used to solve structure: SAPI91 (Fan, 1991); program(s) used to refine structure: TEXSAN; software used to prepare material for publication: TEXSAN.

(I)

Crystal data

C20H42S2	Z = 1
Mr = 346.67	Dx = 1.063 Mg m^−3
Triclinic, P1	Cu Kα radiation, λ = 1.5418 Å
a = 4.2261 (6) Å	Cell parameters from 24 reflections
b = 5.4283 (6) Å	θ = 9.8–17.5°
c = 23.819 (3) Å	µ = 2.17 mm^−1
α = 87.43 (1)°	T = 296 K
β = 86.56 (1)°	Plate, colorless
γ = 83.37 (1)°	0.7 × 0.15 × 0.01 mm
V = 541.4 (1) Å^3

Data collection

Rigaku AFC-5R diffractometer	Rint = 0.045
ω scans	θmax = 70.5°
Absorption correction: ψ (North et al., 1968)	h = −4→5
Tmin = 0.767, Tmax = 0.996	k = −6→2
3008 measured reflections	l = −29→29
1967 independent reflections	2 standard reflections every 150 reflections
1453 reflections with F^2 > 2σ(F^2)	intensity decay: 11.8%

Refinement

Refinement on F^2	H atoms treated by a mixture of independent and constrained refinement
R[F^2 > 2σ(F^2)] = 0.057	w = 1/[σ^2(Fo^2) + {0.05[Max(Fo^2,0) + 2Fc^2]/3}^2]
wR(F^2) = 0.159	(Δ/σ)max = 0.001
S = 1.77	Δρmax = 0.15 e Å^−3
1966 reflections	Δρmin = −0.35 e Å^−3
103 parameters

Special details

Geometry. none

Refinement. Refinement using reflections with F² > -3.0 σ(F²). The weighted R-factor (wR) and goodness of fit (S) are based on F². R-factor (gt) are based on F. The threshold expression of F² > 2.0 σ(F²) is used only for calculating R-factor (gt).

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

	x	y	z	Uiso*/Ueq
S1	1.3470 (2)	−0.2802 (1)	0.05060 (3)	0.0784 (2)
C1	1.1699 (6)	0.0041 (5)	0.08170 (10)	0.0626 (7)
C2	1.0508 (6)	−0.0239 (5)	0.14241 (9)	0.0563 (7)
C3	0.9202 (6)	0.2219 (4)	0.16753 (9)	0.0534 (6)
C4	0.7989 (6)	0.1982 (4)	0.22849 (9)	0.0546 (7)
C5	0.6752 (6)	0.4440 (4)	0.25398 (9)	0.0530 (6)
C6	0.5533 (6)	0.4242 (4)	0.31487 (9)	0.0531 (6)
C7	0.4287 (6)	0.6702 (4)	0.34032 (9)	0.0524 (6)
C8	0.3073 (6)	0.6504 (4)	0.40118 (9)	0.0520 (6)
C9	0.1840 (6)	0.8966 (4)	0.42645 (9)	0.0523 (6)
C10	0.0616 (6)	0.8770 (4)	0.48742 (9)	0.0519 (6)
H1a	1.3258	0.1176	0.0796	0.0752*
H1b	0.9946	0.0700	0.0604	0.0752*
H1s	1.122 (8)	−0.393 (6)	0.050 (1)	0.0942*
H2a	0.8860	−0.1296	0.1445	0.0675*
H2b	1.2226	−0.0971	0.1637	0.0675*
H3a	1.0856	0.3272	0.1653	0.0641*
H3b	0.7490	0.2948	0.1460	0.0641*
H4a	0.6305	0.0959	0.2306	0.0655*
H4b	0.9689	0.1220	0.2498	0.0655*
H5a	0.8440	0.5462	0.2517	0.0636*
H5b	0.5054	0.5199	0.2325	0.0636*
H6a	0.3849	0.3218	0.3172	0.0638*
H6b	0.7232	0.3488	0.3363	0.0638*
H7a	0.5970	0.7728	0.3379	0.0630*
H7b	0.2586	0.7455	0.3189	0.0630*
H8a	0.1386	0.5483	0.4036	0.0624*
H8b	0.4772	0.5748	0.4226	0.0624*
H9a	0.3529	0.9986	0.4241	0.0628*
H9b	0.0144	0.9724	0.4049	0.0628*
H10a	−0.1111	0.7787	0.4905	0.0624*
H10b	0.2284	0.8018	0.5097	0.0624*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0960 (6)	0.0717 (5)	0.0627 (4)	0.0077 (4)	0.0184 (3)	−0.0224 (3)
C1	0.075 (2)	0.063 (1)	0.046 (1)	0.002 (1)	0.010 (1)	−0.009 (1)
C2	0.065 (1)	0.059 (1)	0.041 (1)	0.004 (1)	0.006 (1)	−0.0066 (10)
C3	0.060 (1)	0.054 (1)	0.043 (1)	0.004 (1)	0.0075 (10)	−0.0077 (9)
C4	0.062 (1)	0.056 (1)	0.042 (1)	0.005 (1)	0.007 (1)	−0.0079 (10)
C5	0.060 (1)	0.055 (1)	0.041 (1)	0.004 (1)	0.0071 (10)	−0.0080 (9)
C6	0.062 (1)	0.054 (1)	0.040 (1)	0.003 (1)	0.007 (1)	−0.0082 (9)
C7	0.060 (1)	0.054 (1)	0.040 (1)	0.004 (1)	0.0064 (10)	−0.0079 (9)
C8	0.060 (1)	0.052 (1)	0.040 (1)	0.005 (1)	0.0066 (10)	−0.0083 (9)
C9	0.060 (1)	0.053 (1)	0.041 (1)	0.004 (1)	0.0080 (10)	−0.0084 (9)
C10	0.059 (1)	0.054 (1)	0.039 (1)	0.005 (1)	0.0061 (10)	−0.0071 (10)

Geometric parameters (Å, º)

S1—C1	1.806 (3)	C6—C7	1.516 (3)
C1—C2	1.509 (3)	C7—C8	1.512 (3)
C2—C3	1.518 (3)	C8—C9	1.514 (3)
C3—C4	1.515 (3)	C9—C10	1.515 (3)
C4—C5	1.515 (3)	C10—C10^i	1.512 (4)
C5—C6	1.513 (3)
S1—C1—C2	114.8 (2)	C5—C6—C7	114.6 (2)
C1—C2—C3	112.8 (2)	C6—C7—C8	114.6 (2)
C2—C3—C4	113.8 (2)	C7—C8—C9	114.4 (2)
C3—C4—C5	113.8 (2)	C8—C9—C10	114.4 (2)
C4—C5—C6	114.6 (2)	C9—C10—C10^i	114.3 (2)
C2—C1—S1—H1s	67 (1)

Symmetry code: (i) −x, −y+2, −z+1.