2,5-Bis(1,1,3,3-tetra­methyl­butyl)thio­phene

Hassan Y Elnagar; Mahmood Sabahi; Vince J Gatto; Frank R Fronczek

doi:10.1107/S1600536808037434

. 2008 Nov 20;64(Pt 12):o2396. doi: 10.1107/S1600536808037434

2,5-Bis(1,1,3,3-tetramethylbutyl)thiophene

Hassan Y Elnagar ^a, Mahmood Sabahi ^a, Vince J Gatto ^a, Frank R Fronczek ^b,^*

PMCID: PMC2960047 PMID: 21581366

Abstract

There are two independent molecules in the asymmetric unit of the title compound, C₂₀H₃₆S. Crystals are non-merohedrally twinned by twofold rotation about [001]. The bulky octyl groups of each molecule are on the same side of the thiophene plane and are approximately parallel. S—C distances are in the range 1.729 (4)–1.745 (3) Å, and the C—S—C angles are 92.98 (18) and 93.08 (17)°. The CH₂ groups of the octyl groups are involved in weak C—H⋯S intramolecular interactions.

Related literature

For previous synthetic work, see: Kutz & Corson (1946 ▶); Caeser (1948 ▶). For the catalyst system, see: Elnagar et al. (2006 ▶). For a related structure, see: Krebs et al. (1992 ▶). For a description of the Cambridge Strucural Database, see: Allen (2002 ▶).

Experimental

Crystal data

C₂₀H₃₆S
M _r = 308.55
Monoclinic,
a = 21.2367 (6) Å
b = 7.9954 (2) Å
c = 11.7987 (3) Å
β = 105.059 (2)°
V = 1934.57 (9) Å³
Z = 4
Cu Kα radiation
μ = 1.40 mm⁻¹
T = 90.0 (5) K
0.20 × 0.15 × 0.10 mm

Data collection

Bruker Kappa APEXII diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2004 ▶) T _min = 0.766, T _max = 0.872
9297 measured reflections
9297 independent reflections
9129 reflections with I > 2σ(I)
R _int = 0.029

Refinement

R[F ² > 2σ(F ²)] = 0.070
wR(F ²) = 0.182
S = 1.08
9297 reflections
403 parameters
2 restraints
H-atom parameters constrained
Δρ_max = 1.11 e Å⁻³
Δρ_min = −0.42 e Å⁻³
Absolute structure: 2248/609 Friedel pairs corresponding to each component of the non-merohedral twin.

Data collection: APEX2 (Bruker, 2006 ▶); cell refinement: SAINT (Bruker, 2006 ▶); data reduction: SAINT and ROTAX (Cooper et al., 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶) and CrystMol (Duchamp, 2005 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808037434/fb2113sup1.cif

e-64-o2396-sup1.cif^{(31.9KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808037434/fb2113Isup2.hkl

e-64-o2396-Isup2.hkl^{(445.5KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C8—H8B⋯S1	0.99	2.82	3.301 (4)	111
C16—H16A⋯S1	0.99	2.78	3.243 (4)	109
C28—H28A⋯S2	0.99	2.72	3.209 (4)	111
C36—H36A⋯S2	0.99	2.86	3.312 (4)	108

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supplementary crystallographic information

Comment

Kutz & Corson (1946) first reported acid catalyzed alkylation of thiophene with olefins and alcohols. They suggested that the mono-alkylation reaction occurred at the 2-position of the thiophene ring. Higher boiling liquid products were also isolated, which they believed to be di-alkylated thiophenes. Caeser (1948) synthesized 2,5-di-(1,1,3,3-tetramethylbutyl)thiophene by reacting diisobutylene with thiophene and isolated it as a low-melting solid (b.p. 146–147°C, m.p. 36–37°C). He correctly proposed the structure from its physical properties as well as from the work by Kutz & Corson (1946) on the mono-alkyl derivatives.

The two independent molecules of the asymmetric unit are shown in Fig. 1. Their conformations are quite similar, having both octyl chains on the same side of the thiophene plane. A least-squares fit, overlaying the thiophene and three central C atoms of the octyl groups yields an average deviation (11 atoms) of 0.182 Å, as shown in Fig. 2 (Duchamp, 2005). The thiophene rings in both molecules exhibit maximum deviation 0.011 (4) Å from planarity; it is pertinent for C2 in one molecule and C23 in the other. Some geometric features of the thiophene rings are given in Abstract. The molecules deviate slightly from mirror symmetry, as described by the S—C—C—C torsion angles about the bonds attaching the octyl groups to the thiophenes. Torsion angle magnitudes are about 12° larger on one side of the molecule than on the other: S1—C1—C5—C8 = -59.2 (4) and S2—C24—C33—C36 = -57.1 (4)° vs. S1—C4—C13—C16 = 47.8 (4) and S2—C21—C25—C28 = 44.7 (4)°.

No otherwise unsubstituted thiophenes having tertiary C atoms adjacent to both S atoms are present in the Cambridge Structural Database (Version 5.29 of November 2007; Allen, 2002) except for several macrocyclic molecules: AMADIB, FOJPOK, FOJPUK, FOJQAX, FOJQEB, LOHVEJ, XEMDOJ, XEMFAX, and YOZHEA. The structure of tetra-t-butylthiophene has been reported (Krebs et al., 1992). It has its thiophene twisted out of planarity as a result of the four bulky substituents.

Weak intramolecular C—H···S interactions involving the CH₂ groups of the octyl substituents and the thiophene S atoms are listed in Tab. 1. The C—H···S angles are quite small for this type of interaction, near the tetrahedral angle.

Experimental

Thiophene (42.4 g, 0.50 mol) and diisobutylene (60.8 g, 0.54 mol) were mixed at 20°C, and then the catalyst system containing triethylaluminum (30 ml, 1.0 M solution in heptane, 0.03 mol)/hydrogen chloride (120 ml, 1.0 M solution in ether, 0.12 mol) was carefully added to control the exothermic reaction, under a nitrogen atmosphere (Elnagar et al., 2006). The resulting reaction mixture was heated for 1 h at 80° C. After workup with 12% NaOH solution, the crude product (67.2 g, 87% yield based on diisobutylene) was obtained as a liquid. It solidified upon standing at room temperature. The solidified material was recrystallized from 20% aqueous 2-propanol to obtain colorless plate-like crystals with a melting point range of 36.9–38.1° C. ¹H NMR (CDCl₃) δ 6.57 (s, 2 H), 1.72 (s, 4 H), 1.42 (s, 12 H), 0.86 (s, 18 H); ¹³C NMR (CDCl₃) δ 154.4, 121.3, 58.3, 38.7, 33.1, 32.8, 31.8.