Butane­di­thiol di­acetate

In the solid state, molecules of butane-1,4-diyl bis(S-thio­acetate), C₈H₁₄O₂S₂, are centrosymmetric and are associated via weak hydrogen bonds. The molecular structure, determined by X-ray crystallography, is in good agreement with that obtained by density functional geometry optimization.

Key indicators

• Single-crystal X-ray study
• T = 187 K
• Mean [sigma](C-C) = 0.003 Å
• R factor = 0.048
• wR factor = 0.134
• Data-to-parameter ratio = 18.1

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level B:



RINTA_01  Alert B The value of Rint is greater than 0.15
          Rint given   0.169


 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 0 Alert Level C = Please check

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S1. Comment

Thioesters are very important acetylating agents in biochemical processes, as well as in many chemical transformations (Nicolaou, 1977; Hirama et al., 1979; Zheng et al., 1999). We obtained butanedithiol diacetate, H₃CC(O)SCH₂CH₂CH₂CH₂SC(O)CH₃, (I), as a by-product in the synthesis of 1,4-butanedithiol monoacetate, HSCH₂CH₂CH₂CH₂SC(O)CH₃, (II), in a procedure similar to the preparation of ethanedithiol monoacetate and ethanedithiol diacetate (Wiesler et al., 1996; Fleischer & Schollmeyer, 2001). Crystals of (I) precipitated at 278 K from its solution in (II). They were washed with cold petrol ether and identified by elemental analysis and ¹H NMR. One of them was selected for single-crystal X-ray diffraction.

The molecular structure of (I) as found in the solid state is depicted in Fig. 1. Table 1 shows selected structural parameters from the XRD experiment in comparison to those obtained by a density functional (DF) geometry optimization. The molecular structure was first optimized at the Hartree–Fock level with a 6–31 G(d) basis set, starting from the molecular structure as found in the solid state. Subsequently the structure was re-optimized employing density functional theory (DFT) and a larger basis set [B3LYP/6–311+G(2,p)]. Apart from the two S—C and the C1—C1a distances, the DF bond lengths and angles agree quite well with the experimental values. The torsion angles C1a—C1—C2—S3 and C1—C2—S3—C4 differ substantially between the solid state and the DF-calculated isolated molecule. We attribute the differences in the bond distances mentioned to the chosen level of theory, but the difference in torsion angles to intermolecular hydrogen bridges in the solid state [O5ⁱ···C6 = 3.497 (3) Å and O5ⁱ···H—C6 = 168.1 (2)°; symmetry code: (i) x, 1/2 − y, 1/2 + z]. The structural parameters of (I) agree well with those found for other compounds exhibiting an S-acetyl moiety (Fleischer & Schollmeyer, 2001; Evans et al., 1999; Divajakovic et al., 1992; Mackay et al., 1992; Huber et al., 1984; Mattes & Waldmann, 1983; Mattes et al., 1977; Kiel et al., 1974). This implies that the S-acetyl fragment is a relatively rigid structural unit, a hypothesis supported by an analysis of the bonding situation in terms of natural bond orbitals (Fleischer & Schollmeyer, 2001).

S2. Experimental

Butanedithiol diacetate, (I), was obtained as a by-product in the synthesis of 1,4-butanedithiol monoacetate, (II), in a procedure similar to the preparation of ethanedithiol monoacetate and ethanedithiol diacetate (Wiesler et al., 1996; Fleischer & Schollmeyer, 2001). Crystals of (I) precipitated at 278 K from its solution in (II). They were washed with cold petroleum ether and identified by elemental analysis and ¹H NMR.

S3. Refinement

Chemically equivalent H atoms were refined isotropically with the same displacement parameters. The two different groups of H atoms due to the disordering of the methyl group were treated with two independent displacement parameters. [The CIF contains no H-atom geometry; please supply these data for inclusion in the final CIF]

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: CORINC (Dräger & Gattow, 1971); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: please supply; software used to prepare material for publication: please supply.

Figures

Fig. 1. ORTEPII (Johnson, 1976) view of the centrosymmetric molecule of (I). Displacement ellipsoids are shown at the 50% probability level. H atoms are shown as spheres of fixed radius. The methyl group is disordered (0.52:0.48) and only one set of H atoms bound to C6 is shown.

(I)

Crystal data

C8H14O2S2	F(000) = 220
Mr = 206.31	Dx = 1.310 Mg m^−3
Monoclinic, P21/c	Cu Kα radiation, λ = 1.54178 Å
a = 6.1998 (7) Å	Cell parameters from 25 reflections
b = 8.0292 (7) Å	θ = 57–73°
c = 10.565 (1) Å	µ = 4.31 mm^−1
β = 95.942 (4)°	T = 187 K
V = 523.09 (9) Å^3	Block, colorless
Z = 2	0.25 × 0.20 × 0.15 mm

Data collection

Enraf–Nonius CAD-4 diffractometer	908 reflections with I > 2σ(I)
Radiation source: rotating anode	Rint = 0.169
Graphite monochromator	θmax = 73.8°, θmin = 6.9°
θ/2ω scans	h = −7→7
Absorption correction: ψ scan (CORINC; Dräger & Gattow, 1971)	k = 0→10
Tmin = 0.383, Tmax = 0.524	l = 0→13
1126 measured reflections	3 standard reflections every 60 min
1067 independent reflections	intensity decay: 5%

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)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.134	H-atom parameters constrained
S = 1.12	w = 1/[σ^2(Fo^2) + (0.0915P)^2] where P = (Fo^2 + 2Fc^2)/3
1067 reflections	(Δ/σ)max < 0.001
59 parameters	Δρmax = 0.34 e Å^−3
0 restraints	Δρmin = −0.84 e Å^−3

Special details

Experimental. ψ scans using CORINC (Dräger, 1971)

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	0.5767 (4)	0.4575 (3)	0.4587 (2)	0.0251 (5)
H1A	0.7275	0.4885	0.4896	0.032 (5)*
H1B	0.5468	0.4987	0.3704	0.032 (5)*
C2	0.5571 (4)	0.2683 (3)	0.4584 (2)	0.0268 (5)
H2A	0.6432	0.2226	0.3926	0.037 (5)*
H2B	0.4036	0.2376	0.4347	0.037 (5)*
S3	0.64823 (9)	0.17358 (7)	0.60986 (5)	0.0284 (3)
C4	0.9309 (4)	0.1645 (3)	0.6010 (2)	0.0287 (6)
O5	1.0158 (3)	0.2125 (3)	0.50988 (18)	0.0392 (5)
C6	1.0538 (5)	0.0903 (4)	0.7179 (3)	0.0430 (7)
H6A	0.9519	0.0604	0.7792	0.044 (11)*	0.48
H6B	1.1584	0.1719	0.7564	0.044 (11)*	0.48
H6C	1.1309	−0.0096	0.6942	0.044 (11)*	0.48
H6D	1.2089	0.0880	0.7074	0.062 (12)*	0.52
H6E	1.0024	−0.0234	0.7302	0.062 (12)*	0.52
H6F	1.0299	0.1581	0.7924	0.062 (12)*	0.52

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0297 (12)	0.0258 (11)	0.0197 (10)	0.0031 (9)	0.0025 (9)	0.0007 (8)
C2	0.0316 (12)	0.0266 (11)	0.0209 (10)	0.0038 (9)	−0.0039 (8)	−0.0027 (9)
S3	0.0317 (4)	0.0310 (4)	0.0224 (4)	0.0026 (2)	0.0028 (2)	0.0055 (2)
C4	0.0326 (13)	0.0279 (12)	0.0243 (12)	0.0045 (9)	−0.0034 (9)	−0.0045 (9)
O5	0.0342 (10)	0.0471 (11)	0.0371 (10)	0.0007 (8)	0.0076 (8)	0.0053 (8)
C6	0.0446 (15)	0.0516 (17)	0.0300 (13)	0.0145 (13)	−0.0102 (11)	−0.0019 (12)

Geometric parameters (Å, º)

C1—C1^i	1.517 (4)	S3—C4	1.766 (3)
C1—C2	1.523 (3)	C4—O5	1.207 (3)
C2—S3	1.809 (2)	C4—C6	1.506 (3)
C1^i—C1—C2	113.3 (2)	O5—C4—C6	123.7 (3)
C1—C2—S3	113.55 (15)	O5—C4—S3	123.1 (2)
C4—S3—C2	101.02 (12)	C6—C4—S3	113.2 (2)
C1^i—C1—C2—S3	−67.6 (3)	C2—S3—C4—C6	179.51 (18)
C1—C2—S3—C4	−82.70 (19)	C2—C1—C1^i—C2^i	180.0
C2—S3—C4—O5	−0.8 (2)

Symmetry code: (i) −x+1, −y+1, −z+1.