Biology Reference
In-Depth Information
2.3. Synthesis and Purification of Alkanethiols
The progress of reactions is monitored by thin layer chromatography (TLC)
using 0.25-mm silica gel plates (Merck, Mannheim, Germany, or VWR). Col-
umn chromatography is performed under nitrogen with silica gel (60-200
mesh, Mallinckrodt). Reactions in nonacqueous solvents are carried out under
nitrogen or argon. Organic solvents, unless specified, are HPLC grade
(Mallinckrodt, Phillipsburg, NJ). Tetrahydrofuran (THF) that was used as a
reaction solvent is distilled freshly on a still that contains benzophenone (1 g/L,
Aldrich) and sodium (1 g/L, Aldrich). Dichloromethane used as a reaction sol-
vent is distilled freshly on a still that contains calcium hydride (1 g/L, Aldrich).
NMR spectra were collected on samples dissolved in chloroform- d (Cambridge
Isotope Laboratory). General synthetic procedures are described; the specified
quantities of material can be varied by keeping the molar ratios constants to fit
the needs of each laboratory. More detailed descriptions of basic organic labo-
ratory techniques are found in Zubrick (25) .
2.3.1. Purification of Hexadecanethiol (HDT; 2 mM in ethanol)
Hexadecanethiol (HDT) (Aldrich) is purified by flash chromatography using
hexane as the eluant or by distillation at reduced pressure. The major impurity
is a disulfide. The R f of the product is approx 0.4. The typical 1 H NMR spec-
trum has the following peaks:
δ
1.25 (broad singlet, 29 H), 1.6 (quintet, 2 H),
2.5 (quartet, 2 H).
2.3.2. (1-mercaptoundec-11-yl)tri(ethylene glycol)
(EGT; 2 mM in ethanol) (26-28)
Reaction mixtures are concentrated by rotary evaporation at reduced pres-
sure. The purification of the final product and of the intermediates is carried
out using flash column chromatography with silica gel and 98:2 dichloro-
methane:methanol as the eluant; typical values of R f are provided.
2.3.2.1. U NDEC -1- EN -11- YL ( TRIETHYLENEGLYCOL )
Mix 0.34 mL (4.3 mmol) of 50% aqueous sodium hydroxide with 3.2 g
(21 mmol) of tri(ethylene glycol) (Aldrich) and stir for 30 min in an oil bath at
100
C. Add 1 g (4.3 mmol) of 11-bromoundec-1-ene (Pfaltz and Bauer) and
stir at 100
°
C for 24 h under argon. After cooling, the reaction mixture is
extracted six times with hexane (50-100 mL aliquots), and dried with sodium
sulfate (Aldrich). Combine the hexane portions, concentrate them, and purify
the resulting yellow oil ( R f = 0.3): a typical yield is approx 70%. 1 H NMR (250 MHz)
δ
°
1.2 (broad singlet, 12 H), 1.55 (quintet, J = 7 Hz), 2.0 (quartet, 2 H, J = 7 Hz),
2.7 (broad singlet, 1 H), 3.45 (triplet, 2 H, J = 7 Hz), 3.5-3.8 (multiplet, 12 H),
4.9-5.05 (multiplet, 2 H), 5.75-5.85 (multiplet, 1 H).
Search WWH ::




Custom Search