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A 1-L, round-bottom flask was fitted with a paddle stirrer, reflux condenser, thermometer, and pressure-equalizing dropping funnel. Added successively were 1,2-dichloroethane (531 g, 5.37 mol, 430 ml), methyltricaprylammonium chloride (0.93 g, 2.1 mmol; Adogen 464, Aldrich Chemical Co.), and under nitrogen atmosphere to prevent oxidation, benzenethiol (redistilled, bp 62—64 °C/18 mm; 44.64 g, 40.9 ml; 0.405 mol). It was convenient to feed in nitrogen through the dropping funnel side arm. A bubbler tube with an oil seal that would permit release of excess pressure if necessary was attached to the condenser opening. This device monitored pressure change while maintaining a sealed system. The mixture was stirred vigorously, and a solution of NaOH (20.5 g, 0.500 mol) in water (250 ml) was added at the rate of 33 ml/h during 7.5 h at 23—25 °C, while cooling if necessary. Stirring of the biphasic mixture was continued for 16 h at 20—24 °C. A sample of the aqueous layer showed that none of the benzenethiol remained; GC of the organic layer showed [(2-chloroethyl)thio]benzene and bis-adduct in a molar ratio of greater than 50:1. The upper, aqueous layer was removed by suction tube to a 1-L suction flask. The organic layer was washed by stirring with 1 M HCl (20 mL) and then with water (25 mL). The condenser was replaced by a distillation head and 10-in. Vigreux column, and the liquid mixture was stirred to prevent bumping. An azeotrope of dichloroethane with water distilled first, bp 71—82 °C, followed by dichloroethane, bp 82—83 °C. The azeotrope (50 mL) was used to rinse the reaction flask and then to extract any product from the aqueous layer. The combined organic layer was dried (CaCl2). Liquid product was decanted and the solid rinsed with dry dichloroethane into a distillation (pot) flask which was attached to the Vigreux distillation column and head. All of the dichloroethane was removed when the pot temperature reached 60 °C at a water pump pressure of 13 mm. The liquid residue (70.21 g, 0.406 mol; 100% conversion, by wt) was nearly pure [(2-chloroethyl)thio]benzene. A portion (17.3 g, 100 mmol) was oxidized to pure [(2-chloroethyl)sulfonyl]benzene in 87.1% yield.
The remaining product liquid (52.91 g) was distilled (without Vigreux column) using an oil bath kept at 139—142 °C; this gave [(2-chloroethyl)thio]benzene, bp 122—124 °C/15 mm, 46.00 g (266 mmol; 91.5% yield) (lit. bp 123 °C/14mm) (GC: [(2-chloroethyl)thio]benzene, 99.05%). The residue, 6.85 g, was a mixture of [(2-chloroethyl)thio]benzene, 1,2-bis(phenylthio)ethane, and diphenyl disulfide.
A similar experiment that employed benzenethiol (0.200 mol), 1,2-dichloroethane (6.240 mol), NaOH (0.3385 mol in 250 mL of water), and methyltricaprylammonium chloride (0.60 g; 1.4 mmol) gave [(2-chloroethyl)thio]benzene (30.88 g, 89.4 % distilled yield; GC homogeneous) and residue (2.61 g). The product mixture (before distillation) consisted of 1,2-dichloroethane, 40.58%; [(2-chloroethyl)thio]benzene, 57.92%; diphenyl disulfide, 0.40%; and 1,2-bis(phenylthio)ethane, 0.55% (determined by capillary column GC). Relative amounts were thus: [(2-chloroethyl)thio]benzene, 98.38%; diphenyl disulfide, 0.68%; and 1,2-bis(phenylthio)ethane, 0.94%.
© Collected Ruslan Anatolievich Kiper, burewestnik@mail.ru